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A Besson

Publications and source records attributed to A Besson.

At least 19 recordsLinked to original sources
PubMed2001

Search for heavy particles decaying into electron-positron pairs in pp collisions.

We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.

Journal Article↗
PubMed2001

Quasi-model-independent search for new high p(T) physics at D0.

We apply a quasi-model-independent strategy ("Sleuth") to search for new high p(T) physics in approximately 100 pb(-1) of pp collisions at square root of (s) = 1.8 TeV collected by the D0 experiment during 1992-1996 at the Fermilab Tevatron. We systematically analyze many exclusive final states and demonstrate sensitivity to a variety of models predicting new phenomena at the electroweak scale. No evidence of new high p(T) physics is observed.

Journal Article↗
PubMed2001

Ratio of jet cross sections at square root of s = 630 GeV and 1800 GeV.

The D0 Collaboration has measured the inclusive jet cross section in barpp collisions at square root of s = 630 GeV. The results for pseudorapidities (eta)<0.5 are combined with our previous results at square root of s = 1800 GeV to form a ratio of cross sections with smaller uncertainties than either individual measurement. Next-to-leading-order QCD predictions show excellent agreement with the measurement at 630 GeV; agreement is also satisfactory for the ratio. Specifically, despite a 10% to 15% difference in the absolute magnitude, the dependence of the ratio on jet transverse momentum is very similar for data and theory.

Journal Article↗
PubMed2001

Ratios of multijet Cross Sections in p p collisions at radical(s) = 1.8 TeV.

We report on a study of the ratio of inclusive three-jet to inclusive two-jet production cross sections as a function of total transverse energy in p&pmacr; collisions at a center-of-mass energy sqrt[s] = 1.8 TeV, using data collected with the D0 detector during the 1992-1993 run of the Fermilab Tevatron Collider. The measurements are used to deduce preferred renormalization scales in perturbative O(alpha(3)(s)) QCD calculations in modeling soft-jet emission.

Journal Article↗
PubMed2001

Inclusive jet production in pp(macro) collisions.

We report a new measurement of the pseudorapidity (eta) and transverse-energy ( E(T)) dependence of the inclusive jet production cross section in pp(macro) collisions at square root of s = 1.8 TeV using 95 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron. The differential cross section d(2)sigma/(dE(T)d eta) is presented up to eta = 3, significantly extending previous measurements. The results are in good overall agreement with next-to-leading order predictions from QCD and indicate a preference for certain parton distribution functions.

Journal Article↗
PubMed2001

Search for large extra dimensions in dielectron and diphoton production.

We report a search for effects of large extra spatial dimensions in pp collisions at a center-of-mass energy of 1.8 TeV with the D0 detector, using events containing a pair of electrons or photons. The data are in good agreement with the expected background and do not exhibit evidence for large extra dimensions. We set the most restrictive lower limits to date, at the 95% C.L. on the effective Planck scale between 1.0 and 1.4 TeV for several formalisms and numbers of extra dimensions.

Journal Article↗
PubMed2001

Mitogenic signaling and the relationship to cell cycle regulation in astrocytomas.

The activity and regulation of a number of mitogenic signaling pathways is aberrant in astrocytomas, and this is thought to play a crucial role in the development of these tumors. The cascade of events leading to the formation and the progression from low-grade to high-grade astrocytomas is well characterized. These events include activating mutations, amplification, and overexpression of various growth factor receptors (e.g. epidermal growth factor receptor (EGFR), platelet derived growth factor receptor (PDGFR), c-Met), signaling intermediates (e.g. Ras and Protein kinase C (PKC)), and cell cycle regulatory molecules (e.g. mouse double minute-2 (Mdm2), cyclin-dependent kinase-4 (CDK4), and CDK6), that positively regulate proliferation and cell cycle progression. Inactivating mutations and deletions of signaling and cell cycle regulatory molecules that negatively regulate proliferation and cell cycle progression (e.g. p53, p16/INK4a, p14/ARF, p15/INK4b, retinoblastoma protein (Rb), and Phosphatase and tensin homologue deleted from chromosome 10 (PTEN)) also participate actively in the development of the transformed phenotype. Several mitogenic pathways are also stimulated via an autocrine loop, with astrocytoma cells expressing both the receptors and the respective cognate ligand. Due to the multitude of factors involved in astrocytoma pathogenesis, attempts to target a single pathway have not given satisfactory results. The simultaneous targeting of several pathways or the targeting of signaling intermediates, such as Ras or PKC, situated downstream of many growth factor receptor signaling pathways may show more efficacy in astrocytoma therapy. We will give an overview of how the combination of these aberrations drive astrocytoma cells into a relentless proliferation and how these signaling molecules may constitute relevant therapeutic targets.

Animals↗
PubMed2000

Interleukin-1 is a key regulator of matrix metalloproteinase-9 expression in human neurons in culture and following mouse brain trauma in vivo.

An acute trauma to the CNS rapidly results in the upregulation of inflammatory cytokines that include interleukin-1 (IL-1). We report here that the levels of several matrix metalloproteinases (MMPs) are also elevated following a corticectomy trauma injury to the mouse CNS. The delayed upregulation of MMPs compared to that for IL-1 suggests the possibility that inflammatory cytokines regulate MMP production in CNS trauma. To resolve this, we developed a method to isolate and maintain highly enriched human fetal neurons or astrocytes in culture and examined the regulation by cytokines of the activity of a subgroup of MMPs, the gelatinases (MMP-2 and -9). While both neuronal and astrocytic cultures displayed comparable MMP-2 activity, as evidenced by gelatin zymography, levels of MMP-9 were proportionately higher in neurons compared to astrocytes. Of a variety of cytokines and growth factors tested in vitro, only IL-1beta was effective in increasing the neuronal expression of MMP-9. Finally, an IL-1 receptor antagonist attenuated the increase of neuronal MMP-9 in culture and abolished the injury-induced increase of MMP-9 in the mouse brain. These results implicate IL-1beta as a key regulator of neuronal MMP-9 in culture and of the elevation of MMP-9 that occurs following mouse CNS trauma.

Animals↗
PubMed2000

Effects of the co-administration of mirtazapine and paroxetine on serotonergic neurotransmission in the rat brain.

The alpha(2)-adrenoreceptor antagonist mirtazapine, which is also a 5-HT(2), 5-HT(3) and H(1) receptors antagonist and the selective serotonin (5-HT) reuptake inhibitor paroxetine are effective antidepressant drugs which enhance 5-HT neurotransmission via different mechanisms. The present studies were undertaken to determine whether the mirtazapine-paroxetine combination could induce an earlier and/or a greater effect on the 5-HT system than either drug alone. Using in vivo electrophysiological paradigms, the firing activity of dorsal raphe 5-HT neurons was decreased by 70% in rats treated with paroxetine (10 mg/kg/day, s.c.) for 2 days and was back to normal after 21 days. In contrast, a 2-day treatment with mirtazapine (5 mg/kg/day, s.c.) did not alter the firing of 5-HT neurons whereas it was increased by 60% after 21 days of treatment. A low dose of mirtazapine (5 mg/kg/day, s.c.x2 days) failed to offset the decremental effect of paroxetine on the 5-HT neuron firing activity, but a higher dose (10 mg/kg/day, s.c.x2 days) did attenuate the decremental effect of paroxetine. In the dorsal hippocampus, neither mirtazapine (5 mg/kg/day, s.c.) nor a paroxetine (10 mg/kg/day, s.c.) treatment altered the responsiveness of 5-HT(1A) receptors to microiontophoretically-applied 5-HT. Both in controls and in rats treated for 2 days with paroxetine alone, the administration of the 5-HT(1A) antagonist WAY 100635 (25-100 microg/kg, i.v.) did not change the firing activity of dorsal hippocampus CA(3) pyramidal neurons. However, WAY 100635 increased significantly the firing activity of these neurons in rats treated with mirtazapine alone but to a greater extent with both mirtazapine and paroxetine for 2 days. After 21 days of treatment, WAY 100635 increased to a greater degree the firing rate of CA(3) pyramidal neurons in rats which received the combination over rats given either drug alone. It is concluded that the mirtazapine-paroxetine combination shortened the delay in enhancing the tonic activation of postsynaptic 5-HT(1A) receptors and produced a greater activation of the postsynaptic 5-HT(1A) receptors than either drug given alone. The present results suggested that mirtazapine may have a faster onset of action than a SSRI, and that the co-administration of mirtazapine and paroxetine may accelerate the antidepressant response and as well as being more effective than either drug alone.

Adrenergic alpha-Antagonists↗
PubMed2000

Involvement of p21(Waf1/Cip1) in protein kinase C alpha-induced cell cycle progression.

Protein kinase C (PKC) plays an important role in the regulation of glioma growth; however, the identity of the specific isoform and mechanism by which PKC fulfills this function remain unknown. In this study, we demonstrate that PKC activation in glioma cells increased their progression through the cell cycle. Of the six PKC isoforms that were present in glioma cells, PKC alpha was both necessary and sufficient to promote cell cycle progression when stimulated with phorbol 12-myristate 13-acetate. Also, decreased PKC alpha expression resulted in a marked decrease in cell proliferation. The only cell cycle-regulatory molecule whose expression was rapidly altered and increased by PKC alpha activity was the cyclin-cyclin-dependent kinase (CDK) inhibitor p21(Waf1/Cip1). Coimmunoprecipitation studies revealed that p21(Waf1/Cip1) upregulation was accompanied by an incorporation of p21(Waf1/Cip1) into various cyclin-CDK complexes and that the kinase activity of these complexes was increased, thus resulting in cell cycle progression. Furthermore, depletion of p21(Waf1/Cip1) by antisense strategy attenuated the PKC-induced cell cycle progression. These results suggest that PKC alpha activity controls glioma cell cycle progression through the upregulation of p21(Waf1/Cip1), which facilitates active cyclin-CDK complex formation.

Cell Cycle↗
PubMed2000

[Bankart procedure: clinical and radiological long-term outcome].

PURPOSE OF THE STUDY: There are few reports onlong-term outcome after Bankart procedure. The purpose of this study was to determine the rate of recurrent dislocation, the clinical results and the incidence of glenohumeral osteoarthritis after a minimum 10-year follow-up. MATERIAL AND METHODS: Ninety-seven Bankart procedures were performed in 97 patients between 1972 and 1986 for treatment of anterior shoulder instability with recurrent dislocations. We retrospectively reviewed 74 patients and obtained 64 complete radioclinical evaluations for an average follow-up of 16 years. Clinical evaluation was based on the G. Walch and the Duplay group score but for easier comparisons, we also calculated the Rowe et al. score. Radiographical evaluation was established on the Samilson and Prieto classification but real glenohumeral osteoarthritis with joint narrowing was noted independently as grade four. We also studied the contralateral shoulder. RESULTS: At last follow-up, 7 shoulders (9.5%) had recurrent dislocation, but two of them occurred subsequent to severe trauma over 18 months. Most patients (95 %) were satisfied or very satisfied. Six patients (8.1%) had persistent apprehension but in some it was not due to anterior apprehension. According to the Duplay score (or the Rowe score), 25 shoulders (44.6%) had an excellent result (35/61.4 %) 16 (28.6%) a good result (7/12.3%), 11 (19.7%) a fair result (11.19.3) and 4 (5.4 %) a poor result (4/7%). Operated shoulders were pain free for 75% and painful for forced movements only for 25%. External rotation at 90 degrees of abduction was reduced by 8.7 +/- 15.7 degrees. There was no limitation of internal rotation. Patients returned to preoperative sports activities at the same level for 70.9 % and at a lower level for 12.7%. According to the Samilson classification, 7 (13%) of the shoulders had grade 2 and 2 (3.7%) had grade 3 glenohumeral osteoarthritis. We found 4 cases (7.4%) of real glenohumeral osteoarthritis (grade four) and 2 of these patients had contralateral osteoarthritis of a non unstable shoulder. There was no perioperative complication. DISCUSSION: In our hands the Bankart procedure is appeared as a safe procedure with a low rate of glenohumeral osteoarthritis and a high rate of patient satisfaction.

Adolescent↗
PubMed1999

Dopaminergic and opioidergic mediations of tricyclic antidepressants in the learned helplessness paradigm.

The roles of dopaminergic and opioid neurotransmissions in the activity of three tricyclic antidepressants endowed with different monoamine-reuptake properties [desipramine (DESI), imipramine (IMI), amineptine (AMN)] were examined using a behavioral model of depression in rats; the learned helplessness paradigm. In this model, exposure of rats to inescapable shocks (day 1) produced a subsequent escape deficit in a shuttle box test (days 3, 4, and 5). The escape deficit was reversed by AMN, DESI, and IMI administered twice daily for 5 days (16 and 32 mg/kg/day, p < 0.05, days 3, 4, and 5). In addition, AMN tended to enhance the motor activity of rats during the intertrial intervals, but on the first shuttle-box test only (day 3: p < 0.05, control vs AMN). Haloperidol, a preferential D2 dopamine receptor antagonist, acutely injected IP (37.5 microg/kg), suppressed the behavioral activity of DESI and IMI but not that of AMN. Naloxone, a preferential mu-opioid receptor antagonist, acutely injected IP (0.5 mg/kg), suppressed the behavioral activity of IMI but not that of DESI and AMN. It is concluded that an increased dopaminergic activity is a neurochemical effect common to the different tricyclic antidepressants (via a presynaptic mechanism for AMN and a postsynaptic mechanism for DESI and IMI), whereas an increased mu-opioid neurotransmission does not appear to be essential.

Adrenergic Uptake Inhibitors↗
PubMed1999

PTEN/MMAC1/TEP1 in signal transduction and tumorigenesis.

The level of phosphorylation within cells is tightly regulated by the concerted action of protein kinases and protein phosphatases [Hunter, T. (1995) Cell 80, 225-236]. Disregulation in the activity of either of these players can lead to cellular transformation. Many protein tyrosine kinases are proto-oncogenes and it has been postulated that some protein phosphatases may act as tumor suppressors. Herein we will review the recent findings addressing the roles the candidate tumor suppressor PTEN/MMAC1/TEP1 (PTEN, phosphatase and tensin homologue deleted from chromosome 10; MMAC 1, mutated in multiple advanced cancers 1; TEP1, TGF beta regulated and epithelial cell enriched phosphatase 1) plays in signal transduction and tumorigenesis. PTEN is a dual specificity protein phosphatase (towards phospho-Ser/Thr and phospho-Tyr) and, unexpectedly, also has a phosphoinositide 3-phosphatase activity. PTEN plays an important role in the modulation of the 1-phosphatidylinositol 3-kinase (PtdIns 3-kinase) pathway, by catalyzing the degradation of the PtdIns(3,4,5)P3 generated by PtdIns 3-kinase; this inhibits the downstream functions mediated by the PtdIns 3-kinase pathway, such as activation of protein kinase B (PKB, also known as Akt), cell survival and cell proliferation. Furthermore, PTEN modulates cell migration and invasion by negatively regulating the signals generated at the focal adhesions, through the direct dephosphorylation and inhibition of focal adhesion kinase (FAK). Growth factor receptor signaling is also negatively regulated by PTEN, through the inhibition of the adaptor protein Shc. While some of the functions of PTEN have been elucidated, it is clear that there is much more to discover about the roles of this unique protein.

Animals↗
PubMed1999

[Laxity and functional results of Miller-Galante total knee prosthesis with posterior cruciate ligament sparing after a 6-year follow-up].

PURPOSE OF THE STUDY: The preservation of the posterior cruciate ligament (PCL) was introduced in total knee arthroplasty to improve the quadriceps efficiency and the range of flexion in stairs. The purpose of this study was to determine if these goals were achieved with the Miller-Galante total knee prothesis and to assess the relation between knee laxity and function. MATERIALS AND METHOD: We assessed retrospectively the results of 48 consecutive Miller-Galante with PCL retaining. Four patients were excluded: 2 died, 2 lost to follow-up. Forty-four prostheses were evaluated in 38 patients mean aged 65 (33-79). The preoperative HSS score was 41 +/- 12.4 [21-63]. All the components were cemented with patellar resurfacing (25 metal-backed, 19 polyethylene). Stressed X-rays with Telos device were performed to assess frontal and antero-posterior laxity. All radiographic measurements were carried out with a digitizer (Orthographics). RESULTS: After 6 years of follow-up, 8 prostheses (18.1 p. 100) were already revised because of: 1) 3 excessive anterior tibial translations and severe polyethylene wear; 2) 5 femoro-patellar disorders. These last 5 knees (4 patellar metal-backed) had a greater patellar thickness [(25 mm +/- 1.2) (p = 0.01)]. The mean HSS knee score for the 36 remaining prostheses was 73.8 +/- 11.3 (35-92). Only 5 patients were able to climb stairs without support. The mean mechanical axis was 2.3 degrees in varus, but 81 percent of the knees were at 5 degrees around neutral position. The mean laxity in valgus was 4 degrees +/- 2.3 degrees [1-10], and 4.1 degrees +/- 2.1 degrees [1-9] in varus. The mean anterior tibial translation was 5.3 mm +/- 5 [1-17] and posterior laxity was 4.7 mm +/- 2.5 [1-10]. HSS knee score was lowered by 9 points when frontal laxity (valgus + varus) was greater than 5 degrees (p = 0.01), and by 9.8 points when posterior laxity was 5 mm or more (p = 0.02). The mean thickness of the patella was 22 mm +/- 2.3 [16-27]. DISCUSSION: These results were unsatisfactory considering the high revision rate and the low functional score observed despite of a correct implant positioning. The major challenge for PCL retaining (i.e. free stair climbing) was achieved in few cases. The wide range of posterior laxity underlined the difficulties to control PCL tension. On the other hand, PCL tension has to be controlled as it could influence knee function. Patello-femoral disorders was the main reason for revision surgery and an insufficient patellar bone resection may be contributive. Sagittal anterior laxity was the second reason for revision and it should be carefully detected as it could drive to catastrophic polyethylene wear. CONCLUSION: The advantages of PCL retaining were not demonstrated with this low constrained design. Surgical control of PCL tension could give a wide range of posterior laxity. Sagittal femoral-tibial laxity and femoro-patellar disorders should be detected before severe polyethylene wear. These results advocates for: 1) more congruent designs with PCL retaining or for PCL substituting designs, 2) improvement of patello-femoral design.

Adult↗
PubMed1998

Reversal of learned helplessness by morphine in rats: involvement of a dopamine mediation.

The aim of this study was to examine the role of dopamine neurotransmission in the effects of morphine in the learned helplessness paradigm in rats, a generally recognized model of depression. In this model, rats first exposed to inescapable shocks (stressed rats) exhibited an escape deficit in a subsequent shuttle-box test performed 48 h later for 3 consecutive days. The numbers of escape failures and intertrial crossings (motor activity during each intertrial interval) were recorded. Morphine was injected twice daily for 5 days (6 mg/kg/day, s.c.), and haloperidol, a preferential D2-dopamine receptor antagonist, was injected i.p. 15 min before each shuttle-box session. At the highest dose tested (150 microg/kg) haloperidol mimicked the behavioral deficit produced by inescapable shocks. A 37.5 microg/kg dose of haloperidol, which was ineffective by itself, reversed the morphine-induced improvement of escape behavior in previously stressed rats and the morphine-induced increase in intertrial activity in both stressed and nonstressed animals. These results support roles (a) for a dysregulation of dopaminergic neuronal activity in the expression of escape deficit subsequent to an inescapable aversive situation, and (b) for a dopaminergic mediation in the effects of morphine in the learned helplessness paradigm.

Animals↗
PubMed1998

[Reproducibility of the radiographic analysis of dysplasia of the femoral trochlea. Intra- and interobserver analysis of 68 knees].

PURPOSE OF THE STUDY: The relation between patello-femoral instability and trochlear dysplasia was identified by Dejour. Trochlear dysplasia, diagnosed on knee lateral Xray when the trochlear groove crosses both femoral condyles (the so-called "crossing sign"), must be corrected to improve patello-femoral stability. However surgery should be related to the severity and the shape of trochlear dysplasia, underlining the importance of a reproducible classification. The aim of this study was to establish intra and inter-observer reliability of Dejour's radiographic criteria. MATERIAL: 68 preoperative exact knee profile radiographs were harvested from clinical records of 64 patients who underwent trochleoplasty because of patello-femoral instability and trochlear dysplasia. On these 68 views, the crossing sign was identified by the senior surgeon (F.G.) who performed or supervised surgery. METHOD: The 68 radiographs were examined independently by 7 observers (2 juniors, 5 seniors) in order to assess interobserver agreement. Two juniors repeated the observation to test intraobserver agreement. Reproducibility for categorical data (7 shapes of trochlea according to Dejour (3 for dysplasia)) was evaluated by Kappa statistics, and for numerical data (depth and anterior projection of the trochlear groove with respect to anterior femoral cortex) we used the interclass correlation analysis. RESULTS: Two out of the 7 observers rated all the 68 trochleas as dysplastics. The 5 others rated as normal 1 to 6 trochleas out of the 68. None of the 68 trochleas were recognized with the same shape by the 7 examiners. At best, 6 observers agreed on the same shape and for only 12 trochleas. Disagreement was mostly related to mistakes between type I and type II of dysplasia. For trochlear morphology interobserver agreement was slight (Kappa = 0.17) and intraobserver agreement was fair (Kappa = 0.3). The mean prominence of the trochlea was 3 +/- 2.1 mm [-6 to 10], and the mean trochlea depth was 1 +/- 1.9 mm [0 to 11]. These measurements were more reliable since the interclass correlation coefficients were respectively 0.62 and 0.38. The level of experience of the observers had no influence for categorical or numerical data. DISCUSSION: Our results indicated a low interobserver agreement for trochlear shape identification according to Dejour. The most reliable criteria was measurement of the trochlear prominence which was mostly pathological in our series. The "crossing sign" was reliable to diagnose dysplasia since the probability to rate as normal a true dysplastic trochlea was only 3.1 per cent. However, once the dysplasia diagnosed, this classification gave inconsistent results to select the trochlear shape, particularly for type II. To improve reproducibility we propose to diagnose a type II only when 5 millimeters separate the crossings between the medial and lateral condyles. CONCLUSION: We recommend to use anterior projection of the trochlear groove to rate trochlear dysplasia and to determine the adequate type of trochleoplasty: elevating of the lateral facet if non prominent or deepening of the groove when prominent.

Adolescent↗
PubMed1998

[Treatment of humeral fractures by Marchetti nailing. Apropos of 45 cases].

Between 1995 and 1997 we implanted 45 Marchetti nails. These nails were implanted for traumatic fractures in 39 patients, but also for pathologic fractures in 5 patients. Among these 39 patients, 7 were lost of view, the average age was 60 years. Among these 39 patients, 4 have got an other treatment before which failed. 10 fractures were placed D1, 8 fractures placed D2, 5 fractures placed D3, 16 fractures placed D4 according to the classification of Hackethal modified by De la Caffinière. The fracture type was classified according to A. O. classification: 7 A1, 11 A2, 7 A3, 2 B1, 6 B2, 1 B3, 4 C1, 1 C2. Among the 32 patients reviewed with an average of follow-up of 11 months, we have observed 5 very good results, 14 good results, 6 passable results and 3 bad results (classification of Stewart and Hundley). The average length of consolidation was 3 months. At follow-up the average elbow mobility was 129 degrees. Among the 3 bad results, there were 2 pseudarthrosis, in D4 zone. We have got 3 supracondylar fractures during the removal of the nail and 2 impactions of the metaphysis fracture. 5 patients had a nailing for pathologic fractures, one of them bilateral (4 women and one man, average age 65 years). Only two patients were reviewed, the fracture healed without any difference with the traumatic group. Contrary to other nailing, this materiel respects the rotator cuff. The global functional result was good.

Adolescent↗