PubMed Health⌕ Search

Biomedical subjects

R Brambilla

Publications and source records attributed to R Brambilla.

At least 55 records · Page 3Linked to original sources
PubMed1995

G protein-dependent activation of phospholipase C by adenosine A3 receptors in rat brain.

The recently cloned G protein-coupled adenosine A3 receptor has been proposed to play a role in the pathophysiology of cerebral ischemia. Because phospholipase C activation occurs as a very early response to brain ischemia, we evaluated the ability of A3- selective and nonselective adenosine analogues to elicit phosphoinositide hydrolysis. In myo-[3H]inositol-labeled rat striatal and hippocampal slices, A3 agonists stimulated formation of [3H]inositol phosphates in a concentration-dependent manner. In striatum, the potency order was 2-chloro-N6-(3-iodobenzyl)- adenosine-5'-N-methyluronamide > or = N6-(3-iodobenzyl)- adenosine-5'-N-methyluronamide >> N-methyl-1,3-di-n-butylxanthine-7-beta-D-ribofuronamide > or = 5'-N-ethylcarboxamidoadenosine > or = N6-2-(4-aminophenyl)-ethyladenosine > N6-(p-sulfophenyl)-adenosine = 1,3-dibutylxanthine-7- riboside, which is identical to the potency order in binding studies at cloned rat A3 receptors. Stimulation of phospholipase C activity was abolished by guanosine-5'-O-(2-thiodiphosphate), confirming the involvement of a G protein-coupled receptor. Activation of phospholipase C was higher in the striatum than in the hippocampus, consistent with A3 receptor densities. Stimulation of phospholipase C activity by adenosine analogues was only modestly antagonized by xanthine derivatives and at much higher concentrations than needed for blocking adenosine A1, A2A, and A2b receptors. In the presence of an A1/A2 antagonist, a selective A3 in rat striation. Thus, stimulation of phospholipase C activity agonist only weakly inhibited forskolin-stimulated adenylyl cyclase activity represents a principal transduction mechanism for A3 receptors in mammalian brain, and perhaps A3 receptor-mediated increases of inositol phosphates in the ischemic brain contribute to neurodegeneration by raising intracellular calcium levels.

Adenosine↗
PubMed1994

Disruption of the neurotrophin-3 receptor gene trkC eliminates la muscle afferents and results in abnormal movements.

The trkC gene is expressed throughout the mammalian nervous system and encodes a series of tyrosine protein kinase isoforms that serve as receptors for neurotrophin-3 (NT3), a member of the nerve growth factor (NGF) family of neurotrophic factors. One of these isoforms, gp145trkC/TrkC K1, mediates the trophic properties of NT3 in cultured cells. Here we show that homozygous mice defective for TrkC tyrosine protein kinase receptors lack Ia muscle afferent projections to spinal motor neurons and have fewer large myelinated axons in the dorsal root and posterior columns of the spinal cord. These mice display abnormal movements and postures, indicating that NT3/TrkC-dependent sensor; neurons may play a primary role in proprioception, the sense of position and movement of the limbs.

Amino Acid Sequence↗
PubMed1994

Molecular cloning of PISSLRE, a novel putative member of the cdk family of protein serine/threonine kinases.

Several members of the cdk family of protein kinases are involved in the regulation of the eukaryotic cell cycle. Using a PCR-based strategy we have screened different human tumor cell lines for cdk-related cDNAs. One clone isolated from the bladder carcinoma cell line RT112 encodes a novel protein kinase named PISSLRE, based on its predicted sequence at the conserved PSTAIRE motif. PISSLRE showed 50% amino acid identity with the previously isolated p58KGTA. PISSLRE contained all the structural elements featured by cyclin dependent kinases, including a proline in the PSTAIRE motif, which might be important for cyclin binding. PISSLRE was found expressed as 2.0 kb messenger RNA in a variety of human cell lines. Its expression was not restricted to tumor cells as it was detectable also in normal fibroblasts. In adult tissues, PISSLRE mRNA showed the highest expression in lung, liver and kidney. The broad expression pattern in adult tissues might suggest that PISSLRE could be involved in processes distinct from cell proliferation.

Amino Acid Sequence↗
PubMed1992

Cloning by functional complementation of a mouse cDNA encoding a homologue of CDC25, a Saccharomyces cerevisiae RAS activator.

In the yeast Saccharomyces cerevisiae genetic and biochemical evidence indicates that the product of the CDC25 gene activates the RAS/adenylyl cyclase/protein kinase A pathway by acting as a guanine nucleotide protein. Here we report the isolation of a mouse brain cDNA homologous to CDC25. The mouse cDNA, called CDC25Mm, complements specifically point mutations and deletion/disruptions of the CDC25 gene. In addition, it restores the cAMP levels and CDC25-dependent glucose-induced cAMP signalling in a yeast strain bearing a disruption of the CDC25 gene. The CDC25Mm-encoded protein is 34% identical with the catalytic carboxy terminal part of the CDC25 protein and shares significant homology with other proteins belonging to the same family. The protein encoded by CDC25Mm, prepared as a glutathione S-transferase fusion in Escherichia coli cells, activates adenylyl cyclase in yeast membranes in a RAS2-dependent manner. Northern blot analysis of mouse brain poly(A)+ RNA reveals two major transcripts of approximately 1700 and 5200 nucleotides. Transcripts were found also in mouse heart and at a lower level in liver and spleen.

Adenylyl Cyclases↗
PubMed1991

Characterization of the tyrosine phosphorylation of calpactin I (annexin II) induced by platelet-derived growth factor.

Stimulation in vivo of Swiss 3T3 fibroblasts with platelet-derived growth factor (PDGF) in the presence of orthovanadate induces the tyrosine phosphorylation of a 39 kDa protein, identified as the phosphorylated slow-migrating form of calpactin I (annexin II) heavy chain, p36. In fact, in PDGF-stimulated cells, anti-(calpactin I) antibodies recognize a doublet of bands, p36 and p39, and the latter disappears upon treatment with phosphatase. In many regards phosphorylation of p39 differs from the rapid and transient phosphorylation of the PDGF receptor and of other substrates: (a) it has slower kinetics but is then stable for longer periods of time; (b) it occurs at 37 degrees C but not at 4 degrees C; and (c) whereas most of the tyrosine-phosphorylated proteins are associated with membrane-enriched preparations, membrane association of p39 only occurs in the presence of Ca2+. Moreover, calpactin I leaks out of permeabilized cells at 0.1 microM free Ca2+, whereas it remains associated with the cells at concentrations of Ca2+ greater than or equal to 1 microM. PDGF does not stimulate phosphoinositide turnover (and thus Ca2+ mobilization) at 4 degrees C; thus it can be suggested that the Ca(2+)-dependent translocation of the protein to membrane/cytoskeletal structures is a necessary condition for its phosphorylation. In addition, calpactin I may not be a direct substrate for the PDGF receptor kinase, but rather the substrate of another tyrosine kinase activated by the receptor.

Animals↗
PubMed1991

Bombesin stimulates a high affinity GTPase activity in membranes of Swiss 3T3 fibroblasts.

Peptides of the bombesin family are mitogenic for Swiss 3T3 fibroblasts and in these cells stimulate the turnover of polyphosphoinositides. Recent studies have suggested that G protein(s) may be involved in the signal transduction pathway triggered by bombesin. In this study we have found and characterized a high affinity GTPase activity stimulated by bombesin in membranes of Swiss 3T3 fibroblasts. Our results support the involvement of a G protein in the response of Swiss 3T3 cells to bombesin.

Animals↗
PubMed1990

Kinetics of tyrosine phosphorylation and internalization of human EGF receptors overexpressed in NIH 3T3 fibroblasts.

Binding of epidermal growth factor (EGF) to cells rapidly induces tyrosine phosphorylation of its receptor which is followed by its internalization and dephosphorylation. The kinetics of these processes differs widely in time from minutes to hours according to cell types. In this paper we analyzed EGF receptor phosphorylation and down-regulation in NIH 3T3 cells transfected with the recombinant hEGF-R cDNA which express 4 X 10(5) receptors/cell. In the presence of EGF receptor phosphorylation reached a maximum after 1 min and was then maintained for about 1 h, while during this time the number of EGF-binding sites was reduced to 40% of the initial number. Detailed analysis of the fate of a population of receptors previously activated and autophosphorylated at 4 degrees C, after warming to 37 degrees C in the absence of the ligand, showed that internalization of the cell surface-associated EGF and dephosphorylation of the receptor were rapid (t1/2 15 min) and followed a similar kinetics. Our data indicate that at any given time only a fraction of the total cell surface receptors is phosphorylated on tyrosine and that dephosphorylation occurs at the cell surface or very rapidly after internalization. In addition the data also suggest that a certain recycling of previously internalized receptors may occur in these cells during EGF treatment.

Calcium↗
PubMed1989

Effect of the different dimeric forms of the platelet-derived growth factor on cellular responses in mouse Swiss 3T3 fibroblasts.

PDGF consists of two polypeptide chains, A and B, and all three possible dimers have been isolated from different sources. Human PDGF, essentially AB, porcine PDGF (BB) and recombinant PDGF-AA were tested on Swiss 3T3 fibroblasts for their ability to stimulate mitogenesis, phosphoinositide turnover and tyrosine phosphorylation of the PDGF receptor. When used in saturating amounts, the three isoforms were equally active in inducing mitogenesis. However, PDGF-AA was less active than AB and BB to induce the phosphorylation of the receptor and the turnover of phosphoinositides (30% and 50%, respectively). These findings suggest that, in Swiss 3T3 fibroblasts, PDGF receptors of the alpha-type are present in a slightly lower amount than beta-type. In addition, the two types of receptor appear to have similar physiological functions.

Animals↗
PubMed1989

Inhibition of phosphotyrosine phosphatases reveals candidate substrates of the PDGF receptor kinase.

In normal fibroblasts stimulated by platelet derived growth factor (PDGF), PDGF receptors are transiently phosphorylated on tyrosine and represent the major phosphotyrosine containing protein. The phosphate of the phosphotyrosine groups turns over rapidly, and extensive evidence indicates a dynamic balance between phosphorylation and dephosphorylation reactions. Thus, the effect of an inhibitor of phosphatases, orthovanadate, on the pattern of the tyrosine phosphorylations induced by PDGF in Swiss 3T3 fibroblasts was investigated. Western blot analysis with antibodies against phosphotyrosine indicated that whereas in unstimulated cells no phosphotyrosine containing proteins were detected, treatment of cells with orthovanadate alone elicited the slow phosphorylation of several proteins including a 170 kDa component that was recognized to be the phosphorylated PDGF receptor. Addition of PDGF to cells shortly pretreated with vanadate highly increased the intensity of the 170 kDa band corresponding to the phosphorylated receptor and caused its stabilization during time. In addition, the phosphorylation on tyrosine of other proteins (molecular mass 116, 80, 73, 60, 50 and 39 kDa) was also induced. Both the receptor and the other tyrosine phosphorylated proteins appeared to be associated with the detergent insoluble matrix.

Animals↗
PubMed1989

[Quantitative analysis of the lung CT in normal subjects and in patients with noncardiac pulmonary edema].

A quantitative analysis was performed of the CT images relative to 7 normal human subjects and to 22 patients affected with ARF (Acute Respiratory Failure). The CT scanner image quality was investigated, and the unit was checked with quality control procedures, in order to assure reliability and reproducibility. In every patient the lung was scanned at 3 different levels--basis, hilum and apex. The frequency distribution of CT numbers was studied. The lung areas were calculated for the different conditions, and the data correlated with functional lung data. A method was then tested to evaluate lung weight; the data obtained did not differ from literature data. All the patients were treated with different positive and expiratory pressure (PEEP). For different PEEP values, the quantitative data from CT analysis were correlated with morphofunctional indices.

Adult↗
PubMed1980

[Specificity and sensitivity of pulmonary valve motion in echocardiographic examination as an index of pulmonary hypertension].

Many investigation have been made to establish the role of echocardiography in the diagnosis of pulmonary hypertension based on some parameters derived from the pulmonic valve leaflet echo motion. By observing 160 echo tracings of pulmonary valve motion, the authors calculated the specificity, sensibility and predictive value of these parameters as predictor of pulmonary hypertension, comparing echo data with corresponding haemodynamic determination of pulmonary artery systolic, diastolic and mean pressure and the degree of pulmonary vascular resistances. By means of the statistical analysis of variance correlation between "a" wave depth and severity of pulmonary hypertension was made. "A" wave depth and RPEP/RVET ratio resulted quite sensitive and highly specific indices of pulmonary hypertension, in particular "a" wave depth proved to correlate very well with the level of pulmonary artery systolic, diastolic and mean pressure and with the degree of pulmonary vascular resistances. Highly specific, but not always detectable, was the presence of a midsystolic notch. In conclusion, pulmonary valve echo motion detected by M-mode technique provides useful index of pulmonary hypertension, chiefly by the measurement of "a" wave depth which can also predict its severity.

Echocardiography↗
PubMed1976

An improved method for the separation and quantitation of the modified nucleosides of transfer RNA.

A method is described which allows a very efficient determination of the modified nucleosides of tRNA. The technique involves enzymatic degradation of the tRNA to nucleosides at pH 7.6 and their separation by two-dimensional thin-layer chromatography on cellulose-coated aluminum foils. Based on the analysis of two mammalian tRNAs it is shown that the technique is suitable for the determination of chemically unstable nucleosides as well as the ribose-methylated compounds. At least 36 of the 45 known modified nucleosides can be separated and quantitatively determined by the method described. This procedure is especially suitable for the estimation of the nucleoside composition of unlabeled tRNAs as well as for studying the post-transcriptional modifications of tRNA.

Aluminum↗