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Biomedical subjects

D Oliva

Publications and source records attributed to D Oliva.

At least 91 records · Page 5Linked to original sources
PubMed1987

Introducing EMR children to arithmetical operations: a program involving pictorial problems and distinctive-feature prompts.

This study assessed a program involving distinctive-feature prompts for teaching four EMR children to use the appropriate arithmetical operations (addition, subtraction, multiplication, and division) in the presence of multicomponent pictorial problems. The prompts highlighted critical features of the problems and cued the operations implied. The operations were computed by means of pocket calculators adapted to the response requirements. Training was carried out according to a modified multiple-probe design. Data indicate that the program was effective in establishing the use of operations with all subjects. This behavior was also displayed on problems portraying actions not included in training. The findings are discussed in terms of distinctive-feature prompting, orienting responses, and self-cueing. Attention is given to the generalization of responding across problems, and to educational implications of the program.

Child↗
PubMed1987

Molecular relationship among Salmonella dublin isolates identified at the Center for Enterobacteriaceae of Palermo during the years 1971-85.

A molecular epidemiological study was carried out on 60 Salmonella dublin isolates identified at the Southern Italy Enterobacteriaceae Center between 1971 and 1985. These included 23 isolates from children with diarrhoea in Palermo obtained during 1984. All isolates from the outbreak of gastroenteritis in children were resistant to chloramphenicol and streptomycin and harboured two plasmids of 50 MDa and 3 MDa molecular weight, whereas the majority of the isolates identified before 1984 were susceptible to these antibiotics and carried only a 50 MDa molecular weight plasmid. Four S. dublin strains successively identified from cattle (Palermo, Foggia, Portici) and from a child (Palermo) were shown to possess similar antibiotic resistance patterns and plasmid profiles to S. dublin isolates from the outbreak of gastroenteritis in children. The 50 MDa plasmid was shown to be associated with virulence in mice, while it was not possible to assign any genetic function to the 3 MDa plasmid.

Ampicillin Resistance↗
PubMed1987

(5Z)-carbacyclin discriminates between prostacyclin-receptors coupled to adenylate cyclase in vascular smooth muscle and platelets.

(5E)- and (5Z)-carbacyclin are prostacyclin (PGI2) analogues endowed with antiaggregating and vasodilator properties, which stimulate adenylate cyclase activity in membranes from human platelets and cultured myocytes from rabbit mesenteric artery. In platelets they display the same efficacy as prostaglandin E1 (PGE1), and hence PGI2 both as activators of adenylate cyclase and as inhibitors of aggregation. In contrast, in vascular smooth muscle cells (5Z)-carbacyclin fails to produce the same degree of stimulation of the enzyme as PGI2, (5E)-carbacyclin and PGE1, nor does it induce the maximal relaxation of the mesenteric artery as do the other prostaglandins. (5Z)-carbacyclin is also able to antagonize the activation of adenylate cyclase and the relaxation elicited by PGE1 or PGI2 in the mesenteric artery, and therefore it displays partial agonist properties in these cells. We conclude that the receptors for PGI2 coupled to adenylate cyclase in platelets and vascular smooth muscle cells are different from each other, because (5Z)-carbacyclin can discriminate between them, being a partial agonist at myocyte but not at platelet level.

Adenylyl Cyclases↗
PubMed1987

Characteristics and distribution of specific binding sites for leukotriene C4 in human bronchi.

The binding of [3H]leukotriene (LT) C4 to membranes from human bronchi has been characterized. The specific binding, measured at 4 degrees C, was very rapid, equilibrium being attained within 1 to 5 min. The binding was also rapidly reversible and saturable (maximum binding = 187 pmol/mg of protein). LTC4, LTD4, LTE4 and the LT antagonist FPL 55712 competed with [3H]LTC4 for its binding sites, with the following IC50 values: 0.12; 2.3; 30; and 20 microM. Therefore, the binding sites displayed a higher affinity for LTC4 than for the other sulfidopeptide LTs. Computer-assisted analysis of either the saturation or the competition curves for LTC4 indicated the existence of two classes of binding sites with different affinities (Kd1 and Kd2 = 70 nM and 0.58 microM, respectively), in agreement with the curved semilog plot of the dissociation time course. CaCl2 or MgCl2 increased and GTP or 5'-guanylylimidodiphosphate did not decrease the specific binding. In addition, the distribution of the binding sites for [3H]LTC4 along the human respiratory tree was investigated. At a fixed (10 nM) [3H]LTC4 concentration, membranes obtained from bronchi removed at different levels of the airway tree did not bind LTC4 in a significantly different amount. This is compatible with the finding that LTC4 receptors should be present on bronchi of various caliber, as both small and large airways respond to LTs.

Binding, Competitive↗
PubMed1986

A new case for a presynaptic role of dendrites: an immunocytochemical study of the n. raphé dorsalis.

The distribution of serotonin (5-HT) was determined by the application of the preembedding peroxidase-anti-peroxidase (PAP) technique in vibratome and ultrathin sections of the brain stem. The antiserum stained the neuronal groups B1 to B9. Somata, dendrites and axons of multipolar and bipolar neurons were recognized in the usual locations. The most commonly found profiles in the area of the n. raphe dorsalis were dendrites. The search for axon terminals was unsuccessful. The labeled dendrites appear in synaptic contact with unlabeled endings containing round or pleomorphic vesicles, and occasionally some large dense core vesicles. Contacts between two labeled dendrites or processes were not found. Occasionally a dendrodendritic junction between a 5-HT labeled dendrite and an unlabeled dendrite has been found. There are areas of the dendritic membrane free of synaptic junctions and free of glial insulation. Results are discussed in relation with the previously proposed presynaptic role of the dendrites in the neuronal circuitry of the n. raphé dorsalis.

Animals↗
PubMed1986

Response to heat shock of different sea urchin species.

It is demonstrated that sea urchin embryos of the species Sphaerechinus granularis are able to respond to heat shock by producing heat shock proteins at the same stage as embryos of Paracentrotus lividus, i.e. after hatching. Arbacia lixula embryos are able to synthesize heat shock proteins already at the stage of 64-128 blastomeres. Embryonic survival is observed if the embryos are heated at the stages at which they can synthesize the heat shock proteins. The inhibition of the bulk protein synthesis after heating at 31 degrees C is never less than 50%.

Animals↗
PubMed1986

Acquisition of thermotolerance in sea urchin embryos correlates with the synthesis and age of the heat shock proteins.

Preheating at 31 degrees C induces thermotolerance in Paracentrotus lividus embryos, which therefore become able to withstand 1-h treatment at the otherwise lethal temperature of 35 degrees C, and to develop normally. The acquisition of thermotolerance is positively correlated with the amount of heat shock proteins produced during the 31 degrees C treatment. Evidence is provided that the heat shock proteins, although present in the embryo for long periods after synthesis, lose their effect on thermotolerance within 3 h of the cessation of synthesis.

Acclimatization↗
PubMed1985

Identification of specific binding sites for leukotriene C4 in membranes from human lung.

Leukotriene C4 (LTC4), one of the major components of the slow-reacting substance of anaphylaxis (SRS-A), is a potent constrictor of bronchial smooth muscle in many species including humans. Here we report the identification and characterization of specific binding sites for LTC4 in membranes from human lung parenchyma. At 4 degrees, 3H-LTC4 binding is specific, saturable (Bmax = 32-41 pmoles/mg prot.), rapid (equilibrium being attained within 15 min), reversible and of high affinity (Kd = 3.6-7 X 10(-8) M). The binding sites are sensitive to heat and probably possess a protein moiety, being inactivated upon trypsinization. CaCl2 affects both the association and the dissociation rate and dose-dependently enhances the binding of 3H-LTC4 at equilibrium; maximal enhancement (4-fold) occurred at 10(-2)M CaCl2. Unlabelled LTC4 is able to complete with 3H-LTC4 for its binding sites with an IC50 of 7.8 X 10(-8) M. The addition of 10(-2) M CaCl2 increases the potency of LTC4 in inhibiting the binding (2.2-fold); both the competition curves are monophasic, indicating the existence of a homogeneous class of binding sites. In the presence of CaCl2, LTD4, LTE4 and the SRS-A antagonist FPL 55712 can inhibit 3H-LTC4 specific binding, being, however, less potent than LTC4 (IC50 S = 2.2 X 10(-6), 2.4 X 10(-5) M, for LTD4, LTE4 and FPL 55712, respectively). FPL 55712 displayed a competitive mechanism; its affinity, however, was lower if absorption to glass was not prevented. The present studies indicate that specific binding sites for 3H-LTC4 exist in human lung parenchyma, and that a receptor-mediated process might be involved in the bronchoconstriction induced by LTC4.

Calcium Chloride↗
PubMed1985

Evaluation of novel compounds interacting with H2-histamine receptors: effect on histamine-sensitive adenylate cyclase activity in guinea-pig gastric mucosa.

The activity of a number of compounds belonging to the novel class of N-imidazolylphenyl-N'-alkyl-formamidines on histamine-sensitive adenylate cyclase was evaluated. All substances inhibited histamine-dependent adenylate cyclase activation. The compounds which were investigated in a wider concentration range, i.e. DA 4360, DA 4577, and DA 4626, behaved as simple competitive antagonists, yielding apparent KB values comparable with those estimated in conventional H2-receptor assays. These results provide further evidence for the highly selective H2-receptor antagonism of these new molecules, and confirm the suitability of the histamine-stimulated adenylate cyclase assay in guinea-pig gastric cells as a functionally reduced system for the study of H2 antagonists.

Adenylyl Cyclase Inhibitors↗
PubMed1985

Territorial localization of heat shock mRNA production in sea urchin gastrulae.

In situ hybridization experiments with a labeled DNA probe indicate that the ability to respond to heat shock with the production of the mRNA for the 70 kd heat shock protein is segregated into the ectodermal cells already at the gastrula stage or earlier during the embryonic development of Paracentrotus lividus.

Animals↗
PubMed1985

Differential effects of in vitro ethanol on prostaglandin E1-sensitive adenylate cyclase from smooth muscle cells and platelets.

In membranes of smooth muscle cells cultured from rabbit mesenteric artery, ethanol dose-dependently activates adenylate cyclase, both basal and PGE1- or GPP(NH)P-sensitive. The alcohol increases the maximal stimulation induced by PGE1 and GPP(NH)P, without greatly affecting their potency. The arrhenius plot displays a discontinuity point, which is only slightly lowered by ethanol. On the contrary, in membranes from human platelets ethanol inhibits basal, GPP(NH)P- and PGE1-sensitive adenylate cyclase, without modification of the prostaglandin or guanine nucleotide potency. The break point present in the Arrhenius plots is definitely lowered by the alcohol. In addition, ethanol decreases the thermostability of the enzyme. Neither in myocytes nor in platelets does ethanol affect the activation energy of the reaction. The data suggest that ethanol probably interacts directly with the membrane proteins, and that its effect is not mediated only through a perturbation of membrane lipid fluidity.

Adenylyl Cyclases↗
PubMed1984

6-Keto-prostaglandin E1-sensitive adenylate cyclase and binding sites in membranes from platelets and cultured smooth muscle cells.

6-keto-PGE1 elicits the same biological effects as PGI2 in human platelets and in rabbit aorta and mesenteric artery, being, however, less potent. We report here that 6-keto-PGE1 dose-dependently stimulates adenylate cyclase activity in membranes of human platelets and cultured myocytes from rabbit aorta and mesenteric artery. The extent of stimulation of the enzyme by 6-keto-PGE1 is the same as elicited by PGI2, while the apparent affinity is lower than that of prostacyclin, both in platelets and in vascular smooth muscle cells. At the level of platelet membranes, 6-keto-PGE1 interacts with the binding sites labelled by PGI2. However, in platelets as well as in mesenteric artery myocytes, 6-keto-PGE1 interacts with only one class of sites as demonstrated either by binding or by adenylate cyclase studies, whereas PGI2 in the same conditions recognizes two different classes.

Adenylyl Cyclases↗
PubMed1984

Prostacyclin-sensitive adenylate cyclase in cultured myocytes: differences between rabbit aorta and mesenteric artery.

Prostacyclin relaxes isolated strips of rabbit mesenteric artery and stimulates cholesteryl ester hydrolysis in rabbit aortic smooth muscle cells. Both effects are considered to be mediated by an increase in intracellular cAMP levels. Here we report that prostacyclin, prostaglandin E1 and two stable analogues of prostacyclin (5,6-dihydroprostacyclin and carbacyclin) dose dependently stimulate adenylate cyclase activity in membranes of cultured myocytes from both rabbit aorta and mesenteric artery. The rank order of potency in both systems was prostacyclin greater than carbacyclin greater than prostaglandin E1 greater than 5,6-dihydroprostacyclin, which parallels the order of potency observed for the vasodilator actions. Three other prostanoids, with limited vasoactive properties, prostaglandin D2, BW245C and 6-keto-prostaglandin F1 alpha failed to stimulate significantly adenylate cyclase activity. The two cell types differ in that the enzyme activation in aortic cell involves the interaction of each prostaglandin with one component of the adenylate cyclase system, while in mesenteric arterial cells the activation is brought about by the interaction with a higher and a lower affinity class of components.

Adenylyl Cyclases↗