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D Salvi

Publications and source records attributed to D Salvi.

7 recordsLinked to original sources
PubMed2000

Organic solvent extraction as a versatile procedure to identify hydrophobic chloroplast membrane proteins.

As a complementary approach to genome projects, proteomic analyses have been set up to identify new gene products. One of the major challenges in proteomics concerns membrane proteins, especially the minor ones. A procedure based on the differential extraction of membrane proteins in chloroform/methanol mixtures, was tested on the two different chloroplast membrane systems: envolope and thylakoid membranes. Combining the use of classical sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry analyses, this procedure enabled identification of hydrophobic proteins. The propensity of hydrophobic proteins to partition in chloroform/methanol mixtures was directly correlated with the number of amino acid residues/number of putative transmembrane regions (Res/TM ratio). Regardless of the particular case of some lipid-interacting proteins, chloroform/methanol extractions allowed enrichment of hydrophobic proteins and exclusion of hydrophilic proteins from both membrane systems, thus demonstrating the versatility of the procedure.

Chloroplasts↗
PubMed1998

Selectivity of endotoxin-induced defect in endothelial calcium mobilization.

BACKGROUND: We hypothesized that endotoxin (LPS) would impair bradykinin (BK)-induced calcium (Ca2+) mobilization in aortic endothelial cells, perhaps due to cytotoxicity or via stimulation of nitric oxide (NO) synthesis. As well, we sought to define contributions of LPS-stimulated Ca2+ mobilization to these effects. METHODS: LPS- or BK-induced increments of intracellular Ca2+ were assessed by microspectrofluorimetry with fura-2 in passaged bovine aortic endothelial cells. Time- and dose-dependent effects of LPS exposure (+/- inhibitors of NO or prostaglandin synthesis) on subsequent BK-induced Ca2+ mobilization and on attached cell counts were determined. RESULTS: LPS (0.1 to 1.0 mg/ml) led to rapid increments of Ca2+, while Ca2+ responses were delayed following LPS (1 to 10 microg/ml) and lower doses were without effect. By contrast, LPS more potently (1.0 pg to 1.0 microg/ml) led to dose- and time-dependent impairment of subsequent BK-induced Ca2+ mobilization, with peak effect at four to six hours, persisting for at least 18 hours. This delayed effect on BK-response was unaltered by inhibition of either NO synthase or cyclooxygenase. The effect of LPS on BK-responsivity depended importantly on cell confluence, as it was not observed in subconfluent cells. By contrast, LPS-induced cell detachment, which was observed only at doses > or = 1.0 microg/ml, did not depend on confluence. CONCLUSIONS: Different mechanisms lead to endothelial cytotoxicity and to impaired BK-response following LPS. Only the former effect, occurring at higher doses, might depend on initial LPS-induced Ca2+ mobilization.

Animals↗
PubMed1995

Androgen up-regulates epidermal growth factor receptor expression and binding affinity in PC3 cell lines expressing the human androgen receptor.

Androgens are required for the optimal growth and development of both the normal prostate and steroid-sensitive prostate cancer. PC3 prostate cancer cell lines stably expressing the human androgen receptor (AR) and possessing an androgen-sensitive phenotype (PC3-hAR) were used to examine the role of the epidermal growth factor receptor (EGFR) in androgen-stimulated prostate cancer cell growth. Epidermal growth factor (EGF) and dihydrotestosterone (DHT) independently induced the growth of PC3-hAR cells. Moreover, EGF and DHT in combination exerted a synergistic effect on PC3-hAR cell growth. DHT-exposed PC3-hAR cells expressed a greater than 2-fold increase in EGFR mRNA and 50% more EGFR protein than controls. Time course radioligand-binding assays confirmed these findings by showing an elevation in EGF binding in the DHT-exposed PC3-hAR cells. In addition, radioligand competition-binding studies revealed a 2-fold increase in EGFR-EGF binding affinity in the PC3-hAR cells after DHT treatment. However, no enhancement of transforming growth factor alpha or EGF expression was detected because DHT did not affect the levels of these cytokines in the PC3-hAR cell lysate or conditioned media. Our observations suggest that DHT increases both EGFR number and receptor-ligand affinity in androgen-sensitive prostate cancer cells and that these effects correlate with increased EGF binding and an enhanced mitogenic response to EGF.

Adenocarcinoma↗
PubMed1989

Language use in intergroup contexts: the linguistic intergroup bias.

Three experiments examine how the type of language used to describe in-group and out-group behaviors contributes to the transmission and persistence of social stereotypes. Two experiments tested the hypothesis that people encode and communicate desirable in-group and undesirable out-group behaviors more abstractly than undesirable in-group and desirable out-group behaviors. Experiment 1 provided strong support for this hypothesis using a fixed-response scale format controlling for the level of abstractness developed from Semin and Fiedler's (1988a) linguistic category model. Experiment 2 yielded the same results with a free-response format. Experiment 3 demonstrated the important role that abstract versus concrete communication plays in the perpetuation of stereotypes. The implications of these findings and the use of the linguistic category model are discussed for the examination of the self-perpetuating cycle of stereotypes in communication processes.

Aggression↗
PubMed1986

Effects of high-calcium and/or high-sodium diet on basal and angiotensin II-stimulated blood pressure in the spontaneously hypertensive rat.

Direct conscious blood pressure (BP) was measured via indwelling femoral cannula to evaluate the effects of chronic diet supplements with Na, Ca or both, offered to 3-week-old weanling spontaneously hypertensive rats (SHR). Despite similar food intakes, body weights were reduced within 1-2 weeks on high-Ca diets. Blood pressure was unchanged by 5.5 weeks of diet treatments. However, irrespective of concomitant Na supplement, more prolonged treatment with the high-Ca diet completely abolished the further increase in BP between the 9th and 12th weeks of age, which was noted in the rats fed the normal or high-Na diets. Angiotensin-stimulated BP was attenuated by high-Ca diets regardless of diet Na, similar to basal readings. These weight and pressure effects of Ca were not reproduced by high-Na diet alone. For all four groups, BP was directly and significantly correlated with body weight, both at 9 and 12 weeks of age. These studies demonstrate the potential role of growth retardation in the antihypertensive action of oral Ca loading in young rats.

Angiotensin II↗
PubMed1980

Analogues of formycins A and B: synthesis and some properties of methyl derivatives of 7-amino and 7-keto pyrazolo(4,3-d)pyrimidines.

Starting from the synthesis of 3-propyl-7-ketopyrazolo(4,3-d)pyrimidine (a formal analogue of formycin B), this was converted to the 7-thio derivative, which was aminated to give 3-propyl-7-aminopyrazolo(4,3-d(pyrimidine (a formal analogue of formycin A) and its methylamino derivatives. With the aid of different methylating agents, all four possible ring N-mono-methyl derivatives of the foregoing have been synthesized. Dimethyl derivatives were prepared on a small scale and identified by cross-methylation reactions, spectral properties and chromatographic behaviour. The basic physico-chemical properties of all the foregoing are described, including ultraviolet absorption spectra, spectrophotometrically determined pK values, and the 1H chemical shifts in aqueous medium and/or dimthjyl sulphoxide. The spectral properties of the various analogues indicate that the N6-methyl derivatives exist predominantly in the imino form, in contrast to the predominant amino form of the corresponding analogue from the adenine series, N1-methyladenine, but similar to the fixed imino form of N1-methyl-9-substituted adenines.

Amination↗