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M Pelosi

Publications and source records attributed to M Pelosi.

At least 19 recordsLinked to original sources
PubMed2006

The Akt signaling pathway determines the different proliferative capacity of chronic lymphocytic leukemia B-cells from patients with progressive and stable disease.

Chronic lymphocytic leukemia (CLL) B-cells are hyporesponsive to many proliferative signals that induce activation of normal B-lymphocytes. However, a heterogeneous response has recently been observed with immunostimulatory CpG-oligodeoxynucleotides (CpG ODN). We now show that CpG ODN induce proliferation mainly in CLL B-cells from patients with progressive disease and unmutated immunoglobulin V(H) genes, whereas G(1)/S cell cycle arrest and apoptosis are induced in leukemic B-cells from stable/V(H) mutated CLL. Examination of early signaling events demonstrated that all CLL B-cells respond to CpG ODN stimulation by degradation of the NF-kappaB inhibitor IkappaB and activation of the Akt, ERK, JNK and p38 MAPK kinases, but the magnitude and duration of the signaling response was greater in the proliferating cases. Pharmacological inhibition of these pathways showed that simultaneous activation of Akt, ERK and JNK is required for cell cycle progression and proliferation. Conversely, introduction of constitutively active Akt in nonproliferating CLL B-cells resulted in induction of cyclin A following CpG ODN stimulation, indicating that increased Akt activation is sufficient to overcome the hyporesponsiveness of these cells to proliferative signals. Thus, the magnitude of Akt signaling may determine the distinct responses observed in leukemic B-cells belonging to the different prognostic subgroups.

Adult↗
PubMed2001

A potential role for protein tyrosine kinase p56(lck) in rheumatoid arthritis synovial fluid T lymphocyte hyporesponsiveness.

Rheumatoid arthritis (RA) synovial fluid (SF)-T lymphocytes appear relatively inactive in situ and respond only weakly to diverse stimuli ex vivo. To characterize the molecular defects underlying this hyporesponsiveness we analyzed the expression level of several proteins involved in TCR-proximal signal transduction. As compared to peripheral blood (PB)-T lymphocytes, SF-T cells from some (but not all) of the patients analyzed expressed lower levels of TCRalphabeta, CD3epsilon, TCRzeta, p56(lck) and LAT, while p59(fyn), phospholipase C-gamma1 and ZAP-70 expression was unaltered. Semi-quantitative analysis of T cells from several patients revealed that the degree of TCRzeta chain and p56(lck) modulation correlated statistically significantly with the level of SF-T cell hyporesponsiveness. The differential reactivity of p56(lck) specific monoclonal and polyclonal antibodies in SF-T but not PB-T lymphocytes indicated that p56(lck) modulation consists of a conformational change rather than loss of expression. Our results indicate that multiple signaling molecules can be modulated in RA SF-T cells and show for the first time a direct quantitative correlation between T cell hyporesponsiveness and modulation of TCRzeta and of p56(lck), a critical protein tyrosine kinase required for T cell activation.

Adult↗
PubMed2000

Localization, purification, and characterization of the rabbit sarcoplasmic reticulum associated calmodulin-dependent protein kinase.

The Ca2+/calmodulin dependent protein kinase associated with the sarcoplasmic reticulum membranes (SR CaM kinase) plays a specific and important role in the modulation of both Ca2+ uptake and release functions of the sarcoplasmic reticulum itself. In this work we have localized a 60 kD SR CaM kinase in slow and fast twitch rabbit skeletal muscle fractions; the kinase was present in both the longitudinal and the junctional sarcoplasmic reticulum. We then developed a procedure for the purification of the active kinase from the longitudinal sarcoplasmic reticulum and performed biochemical and functional characterization of the enzyme. Differently from what was previously suggested, our analysis shows that the biochemical properties of the purified SR CaM kinase (Ca2+ sensitivity, K0.5 for calmodulin, Km for ATP, IC50 for the specific inhibitory peptide (290-309), autophosphorylation properties) are not significantly different from those of the soluble multifunctional CaM kinase II. Moreover, we show that the purified SR CaM kinase retains the ability to autophosphorylate in a Ca2+/calmodulin-dependent manner, becoming a Ca2+-independent enzyme. In the light of the knowledge of the rabbit SR CaM kinase biochemical properties, we propose and discuss the possibility that, under physiological conditions, the activity of the autophosphorylated kinase persists when the Ca2+ transient is over.

Animals↗
PubMed1999

Tyrosine 319 in the interdomain B of ZAP-70 is a binding site for the Src homology 2 domain of Lck.

T-cell antigen receptor-induced signaling requires both ZAP-70 and Lck protein-tyrosine kinases. One essential function of Lck in this process is to phosphorylate ZAP-70 and up-regulate its catalytic activity. We have previously shown that after T-cell antigen receptor stimulation, Lck binds to ZAP-70 via its Src homology 2 (SH2) domain (LckSH2) and, more recently, that Tyr319 of ZAP-70 is phosphorylated in vivo and plays a positive regulatory role. Here, we investigated the possibility that Tyr319 mediates the SH2-dependent interaction between Lck and ZAP-70. We show that a phosphopeptide encompassing the motif harboring Tyr319, YSDP, interacted with LckSH2, although with a lower affinity compared with a phosphopeptide containing the optimal binding motif, YEEI. Moreover, mutation of Tyr319 to phenylalanine prevented the interaction of ZAP-70 with LckSH2. Based on these results, a gain-of-function mutant of ZAP-70 was generated by changing the sequence Y319SDP into Y319EEI. As a result of its increased ability to bind LckSH2, this mutant induced a dramatic increase in NFAT activity in Jurkat T-cells, was hyperphosphorylated, and displayed a higher catalytic activity compared with wild-type ZAP-70. Collectively, our findings indicate that Tyr319-mediated binding of the SH2 domain of Lck is crucial for ZAP-70 activation and consequently for the propagation of the signaling cascade leading to T-cell activation.

Amino Acid Sequence↗
PubMed1999

Tyrosine 319, a newly identified phosphorylation site of ZAP-70, plays a critical role in T cell antigen receptor signaling.

Following T cell antigen receptor (TCR) engagement, the protein tyrosine kinase (PTK) ZAP-70 is rapidly phosphorylated on several tyrosine residues, presumably by two mechanisms: an autophosphorylation and a trans-phosphorylation by the Src-family PTK Lck. These events have been implicated in both positive and negative regulation of ZAP-70 activity and in coupling this PTK to downstream signaling pathways in T cells. We show here that Tyr315 and Tyr319 in the interdomain B of ZAP-70 are autophosphorylated in vitro and become phosphorylated in vivo upon TCR triggering. Moreover, by mutational analysis, we demonstrate that phosphorylation of Tyr319 is required for the positive regulation of ZAP-70 function. Indeed, overexpression in Jurkat cells and in a murine T cell hybridoma of a ZAP-70 mutant in which Tyr319 was replaced by phenylalanine (ZAP-70-Y319F) dramatically impaired anti-TCR-induced activation of the nuclear factor of activated T cells and interleukin-2 production, respectively. Surprisingly, an analogous mutation of Tyr315 had little or no effect. The inhibitory effect of ZAP-70-Y319F correlated with a substantial loss of its activation-induced tyrosine phosphorylation and up-regulation of catalytic activity, as well as with a decreased in vivo capacity to phosphorylate known ZAP-70 substrates, such as SLP-76 and LAT. Collectively, our data reveal the pivotal role of Tyr319 phosphorylation in the positive regulation of ZAP-70 and in TCR-mediated signaling.

Amino Acid Sequence↗
PubMed1999

MRI appearance of placenta percreta and placenta accreta.

The purpose of this paper is to describe the magnetic resonance imaging (MR) features of placenta accreta and percreta. We retrospectively reviewed MRI findings in four cases of placenta accreta/percreta to determine features which assist in identifying the presence and extent of placental implantation abnormality. All patients had ultrasound (US) examinations. Pathologic correlation was available in all cases. There were two cases of placenta percreta and two cases of placenta accreta. All cases were treated by hysterectomy. In the two cases of placenta percreta, the placenta demonstrated transmural extension through the uterus (percreta) on MRI. In the two cases of placenta accreta, the location of thinning in the uterine wall correlated with the location of placental invagination into the myometrium at pathology. US correlation was available in all four cases. Gray scale US did not demonstrate placental invasion in any of the four cases of placenta accreta/percreta, however, in two of three cases in which color Doppler was performed, there was flow at the uterine margin suspicious for implantation abnormality. In conclusion, MRI is useful for identifying the presence and extent of placenta accreta/percreta.

Adult↗
PubMed1999

MRI appearance of cervical incompetence in a pregnant patient.

Ultrasonography is currently the principal imaging modality for diagnosing cervical incompetence during pregnancy. Various technical factors, both patient and technologist/transducer related, may limit its evaluation for cervical incompetence. MRI is not dependent on these technical considerations. MRI may demonstrate a higher degree of soft tissue contrast than ultrasonography for depicting uterine anatomy. MRI may, in some instances, be more accurate in depicting cervical incompetence in the gravid patient. We present the first case of cervical incompetence in a pregnant patient diagnosed by MRI, in which ultrasonography failed to provide conclusive evidence of extra-uterine herniation of the amniotic sac.

Adult↗
PubMed1996

Colocalization of the dihydropyridine receptor, the plasma-membrane calcium ATPase isoform 1 and the sodium/calcium exchanger to the junctional-membrane domain of transverse tubules of rabbit skeletal muscle.

The subcellular distribution of the calmodulin-stimulated plasma-membrane Ca(2+)-ATPase (PMCA) has been studied in rat and rabbit skeletal muscle cells by indirect (calmodulin gel overlays) and direct (Western blotting with specific antibodies) methods. It has also been studied in situ in immunocytochemistry experiments. The distribution of PMCA has been compared with that of the NA+/Ca2+ exchanger and of the dihydropyridine receptor, which has been studied by Western blotting with specific antibodies. Both PMCA and the Na+/Ca2+ exchanger had a dual localization, i.e., they were found in the plasma membrane and in the transverse-tubule fractions of the two main types of skeletal muscles studied. The pump and the exchanger were not diffusely distributed in the transverse-tubule-membrane system, but specifically confined to the membrane domain where the dihydropyridine receptor was also localized, i.e., the junctional membrane. Experiments with isoform-specific antibodies have shown that the pump isoform expressed in skeletal muscle is PMCA 1.

Animals↗
PubMed1996

Skeletal muscle sarcoplasmic reticulum phenotype in myotonic dystrophy.

In this study we investigated the sarcoplasmic reticulum (SR), alongside myofibrillar phenotype, in muscle samples from five Myotonic Dystrophy (DM) patients and five control individuals. DM muscles exhibited as a common feature, a decrease in the slow isoform of myosin heavy chain (MHC) and of troponin C in myofibrils. We observed a match between myofibrillar changes and changes in SR membrane markers specific to fiber type, i.e. the fast (SERCA1) Ca(2+)-ATPase isoform increased concomitantly with a decrease of protein phospholamban (PLB), which in native SR membranes colocalizes with the slow (SERCA2a) SR Ca(2+)-ATPase, and regulates its activity depending on phosphorylation by protein kinases. Our results outline a cellular process selectively affecting slow-twitch fibers, and non-degenerative in nature, since neither the total number of Ca(2+)-pumps or of ryanodine receptor/Ca(2+)-release channels, or their ratio to the dihydropyridine receptor/voltage sensor in junctional transverse tubules, were found to be significantly changed in DM muscle. The only documented, apparently specific molecular changes associated with this process in the SR of DM muscle, are the defective expression of the slow/cardiac isoform of Ca(2+)-binding protein calsequestrin, together with an increased phosphorylation activity of membrane-bound 60 kDa Ca(2+)-calmodulin (CaM) dependent protein kinase. Enhanced phosphorylation of PLB by membrane-bound Ca(2+)-CaM protein kinase also appeared to be most pronounced in biopsy from a patient with a very high CTG expansion, as was the overall 'slow-to-fast' transformation of the same muscle biopsy. Animal studies showed that endogenous Ca(2+)-CaM protein kinase exerts a dual activatory role on SERCA2a SR Ca(2+)-ATPase, i.e. either by direct phosphorylation of the Ca(2+)-ATPase protein, or mediated by phosphorylation of PLB. Our results seem to be consistent with a maturational-related abnormality and/or with altered modulatory mechanisms of SR Ca(2+)-transport in DM slow-twitch muscle fibers.

Adolescent↗
PubMed1984

Bacterial colonization of amniotic fluid in patients with intact membranes during labor.

Amniotic fluid from gravidas with intact membranes was obtained for bacteriologic culture at the time of cesarean section. The incidence of positive cultures from patients not in labor was 8%. When the length of labor was eight hours or less (mean 6.1 hours) and the membranes were intact, the incidence of positive cultures was 37%; in patients whose length of labor was 12 hours or less (mean 9.7 hours) with intact membranes, 55% of cultures were positive. The incidence of endomyometritis in patients with bacterial growth from the amniotic fluid cultures in each group was 33%, 33%, and 45%, respectively.

Amniotic Fluid↗
PubMed1982

Prophylactic antibiotics for cesarean section: comparison of high- and low-risk patients for endomyometritis.

The efficacy of ticarcillin in the prevention of post-cesarean section endomyometritis was studied in 259 women randomly given either the antibiotic or a placebo. The ticarcillin group received 6 g intravenously immediately after delivery. Then 22 of those patients were also given a second 3-g dose 6 to 8 hours after delivery. Among the 139 patients who received ticarcillin, endomyometritis developed in 44 (32%), as it did in 66 of 120 patients (55%) in the placebo group. These differences are highly significant (P = .002). Of the 259 patients in the study, 238 could be classified as to risk for endomyometritis developing. Among the 124 high-risk patients, 52 received a placebo and endomyometritis developed in 71%. Only 26 of the 72 high-risk patients who received ticarcillin (36%) were so infected. Among the low-risk patients, endomyometritis developed in 10 of 54 patients (18.5%) who received prophylaxis and in 24 of 60 patients who received placebo (40%). Ticarcillin appears to be effective in reducing the incidence of post-cesarean section endomyometritis in patients at high risk and in those at low risk. The number of pelvic examinations during labor was the most important single factor in the development of endomyometritis.

Adult↗
PubMed1975

Prophylactic internal iliac artery ligation at cesarean hysterectomy.

One hundred and eight preplanned cesarean hysterectomies have been evaluated in an effort to determine that advisability of prophylactic bilateral hypogastric artery ligation when there is anticipated heavy bleeding associated with surgery. The data indicates that prophylactic bilateral internal iliac artery ligation is of questionable value in reducing operative bleeding, which can be controlled by more conventional means. However, when used therapeutically, it may be a lifesaving operation. Familiarity with the procedure is necessary for all those performing operative obstetrics and gynecology.

Adult↗
PubMed1975

Renal carcinoma in pregnancy.

A gravid patient presented with gross hematuria in the last trimester of pregnancy but did not permit diagnostic measures. After delivery a large abdominal mass, which proved to be renal cell carcinoma, was found. Previously reported cases are reviewed, and the importance of adequate workup of hematuria during pregnancy is emphasized.

Adenocarcinoma↗
PubMed1975

Comparison of sterilization by tubal ligation and hysterectomy.

A comparison was made between sterilization by hysterectomy and by tubal ligation at the time of cesarean section and as an interval procedure. All operations were done at one institution and, essentially, by the same physician population, allowing for promotion within the residency program. The major deterrent to hysterectomy was the associated high incidence of necessary blood transfusion. However, a hysterectomy does offer the benefits of a permanent and completely effective procedure and the removal of an organ which ultimately may be the source of other problems. If another pathologic condition exists, making ultimate hysterectomy likely, it is the procedure of choice for sterilization, avoiding risks, costs, and the inconvenience of another operation. Methods of elective sterilization must be individualized. If the patient is appraised of the increased risk of hysterectomy and desires this more definitive procedure on the basis of informed consent, the incidence of complications is not prohibitive. These should not deter the well trained surgeon but should mandate use of all available skills, intensive evaluation of the patient, and concerned recognition of the potential adverse consequences.

Abscess↗