Strain-Gradient Position Mapping of Semiconductor Quantum Dots.

We introduce a nondestructive method to determine the position of randomly distributed semiconductor quantum dots (QDs) integrated in a solid photonic structure. By setting the structure in an oscillating motion, we generate a large stress gradient across the QDs plane. We then exploit the fact that the QDs emission frequency is highly sensitive to the local material stress to map the position of QDs deeply embedded in a photonic wire antenna with an accuracy ranging from ±35 nm down to ±1 nm. In the context of fast developing quantum technologies, this technique can be generalized to different photonic nanostructures embedding any stress-sensitive quantum emitters.

Strain-mediated coupling in a quantum dot-mechanical oscillator hybrid system.

Recent progress in nanotechnology has allowed the fabrication of new hybrid systems in which a single two-level system is coupled to a mechanical nanoresonator. In such systems the quantum nature of a macroscopic degree of freedom can be revealed and manipulated. This opens up appealing perspectives for quantum information technologies, and for the exploration of the quantum-classical boundary. Here we present the experimental realization of a monolithic solid-state hybrid system governed by material strain: a quantum dot is embedded within a nanowire that features discrete mechanical resonances corresponding to flexural vibration modes. Mechanical vibrations result in a time-varying strain field that modulates the quantum dot transition energy. This approach simultaneously offers a large light-extraction efficiency and a large exciton-phonon coupling strength g0. By means of optical and mechanical spectroscopy, we find that g0/2 π is nearly as large as the mechanical frequency, a criterion that defines the ultrastrong coupling regime.

[Beneficial effect of cochlear implants in the elderly]. / Bénéfice de l'implant cochléaire chez le sujet âgé.

OBJECTIVE: To evaluate the benefit of cochlear implantation in older adults aged 60 Years and over. METHODS: Fifty-six profoundly or totally hearing-impaired patients, aged 60 Years and over, were studied retrospectively. At the end of the preoperative evaluation, 28 patients received a cochlear implant. The mean age was 66 Years and the median follow-up was 22.5 Months. Speech perception scores before and after implantation were analyzed in order to evaluate the benefit of cochlear implantation. The speech perception score before implantation was compared to that of the non-implanted patients. RESULTS: There was a significant improvement of the dissyllabic words and sentences scores after implantation. The patients who are over 70 Years performed as well as those who are younger (between 60 and 70 Years). One patient developed a postoperative vertigo due a perilymphatic fistula. There was no flap-related problems. In the non-implanted group (mean age: 68 Years), 18 patients declined the cochlear device because they thought the subjective benefit of their hearing aid was sufficient and 5 patients declined because of surgical risk. The mean age, the cause and the duration of the deafness, and the speech perception scores were similar between implanted and non-implanted patients. CONCLUSION: This study demonstrates the beneficial effect of cochlear implantation in the elderly. These results suggest that a similar benefit could have been obtained in the patients who declined surgery. An early implantation could reduce the duration of the deafness and preserve binaural sound perception allowing increased performance in older people.

Thrombin induces angiogenesis and vascular endothelial growth factor expression in human endothelial cells: possible relevance to HIF-1alpha.

The serine protease thrombin present at the site of vascular injury triggers fibrin formation, platelet activation and different cellular responses including angiogenesis. We report a role for thrombin in the human monolayer cultured endothelial cell growth and angiogenesis in 3D collagen gel angiogenesis assay. The angiogenic activity of thrombin is, in part, related to the expression of the vascular endothelial growth factor (VEGF)165 mRNA, assessed by reverse transcriptase-polymerase chain reaction, either in monolayer cultured endothelial cells or in endothelial cells forming capillary-like structures in the 3D collagen gel assay. This expression of VEGF mRNA is associated with a VEGF secretion in the supernatant of thrombin-treated human umbilical vein endothelial cells. The thrombin-induced VEGF165 mRNA expression is associated with the regulation of hypoxia-inducible factor 1alpha, analyzed by Western Blot, in endothelial cells.

Embolized ischemic lesions of toes in an afibrinogenemic patient: possible relevance to in vivo circulating thrombin.

Fibrinogen plays a complex role in hemostasis, thrombosis, and vascular disease. Hyperfibrinogenemia is an independent vascular risk factor and dysfibrinogenemia can provoke thrombosis. Afibrinogenemia is usually responsible for hemorrhagic diathesis, and unexpected ischemic lesions are intriguing. We report the case of an afibrinogenemic patient, who at the age of 30 developed ischemic lesions of the feet related to severe stenosis of the iliac and hypogastric arteries. The biopsy of the iliac artery lesion showed an intense myointimal hyperplasia. We performed standard hemostatic analysis and analyzed the activation markers of platelets and coagulation factors and the kinetics of thrombin generation in the patient and in normal control plasmas treated or not with reptilase. Occlusive arterial lesions were attributed to a disruptive hematoma penetrating the vascular lumen. Thrombin concentration after calcium addition increase markedly in the afibrinogenemic patient and in defibrinated normal plasma, as compared to untreated normal plasma. Thrombin-antithrombin complexes (T-AT) were markedly enhanced while F1+2 prothrombin fragments stayed in the normal range. These results suggested activation of coagulation and in vivo circulating thrombin. Thrombin activates the platelets that secrete growth factors for smooth muscle cells and generate the intimal hyperplasia. Recurrent hemorrhage within the vessel wall might induce injury and local thrombin generation. Thrombin not trapped by the clot is available for platelet activation and smooth muscle cell migration and proliferation. The absence of a protective fibrin cap on the intima might account for intima vulnerability and embolization. Afibrinogenemia appears in this paradoxical situation as a vascular risk factor.

[Behcet's disease manifested as a intracranial aneurysm]. / Maladie de Behçet révélée par un anévrisme intracrânien.

INTRODUCTION: Mostly venous (95% of all vascular complications), and less frequently arterial (2 to 7% of all cases), vascular complications are commonplace in Behçet's disease (23 to 64% of the patients, depending on the series). Arterial complications are stenosis, occlusions and especially severe due to their unpredictable rupture risk, aneurysms. Intracranial aneurysms associated with Behçet's disease are exceptional. Until now, only ten cases have been published. EXEGESIS: We report the case of a 36-year-old patient of Armenian origin in whom the diagnosis of Behçet's disease was made after a subarachnoid hemorrhage caused by the rupture of a left superior cerebellar artery aneurysm. The endovascular treatment of the aneurysm was associated with an immunosuppressive treatment consisting of cyclophosphamide, corticoids and colchicine. Within a 6-month period of follow up the evolution has been favorable. This is the first published case report of Behçet's disease associated with an aneurysm of the posterior circulation treated endovascularly. A review of the literature is also included. CONCLUSION: Intracranial aneurysms are an exceptional but nevertheless severe localization of vascular complications in Behçet's disease. As in all other arterial lesions, recurrences are frequent. The treatment involves surgical or endovascular treatment that should be associated with corticoids and immunosuppressive therapy. Colchicine is useful for the prevention of relapses.

[Homocysteine, 5,10-methylenetetrahydrofolate reductase and deep venous thrombosis. Survey of 120 patients in internal medicine]. / Homocystéine, 5,10-méthylènetétrahydrofolate réductase et thrombose veineuse profonde. Enquête auprès de 120 patients en médecine interne.

BACKGROUND: In the last few years, the association of deep vein thrombosis with frequent biological risk factors and genetic polymorphisms has significantly modified the field of venous thrombosis. In this study, we measured plasma homocysteine levels and tested the C677T methylenetetrahydrofolate reductase (MTHFR) mutation. PATIENTS AND METHODS: Plasma homocysteine levels and test for C677T MTHFR mutation were performed in 120 consecutive patients with objectively diagnosed deep vein thrombosis, and in 120 controls. RESULTS: We found a strong association between hyperhomocysteinemia and thrombosis (odd ratio: 2.43 IC 95% [1.27-4.7]). Conversely the C677T MTHFR gene polymorphism is only associated with hyperhomocysteinemia but not associated with thrombosis. CONCLUSION: This is a preliminary study to the ongoing international multicentric study of SNFMI (Société nationale française de m0+edecine interne) concerning hyperhomocysteinemia and venous thrombosis.

Induction of endothelial cell adhesion molecules by serum and immunoglobulins G from a patient with vasculitis and monoclonal gammapathy: potential relevance to vasculitis.

Interactions between endothelial cell adhesion molecules and their beta2 integrin adhesive receptors on leukocytes are thought to play a role in the pathogenesis of inflammatory diseases and probably vasculitis. We describe a case in whom leukocytoclastic vasculitis was associated to a monoclonal immunoglobulin G2 kappa (IgG2K). During the vasculitic crisis, the patient's serum and the isolated IgG from this serum induced the expression of E-selectin, VCAM-1 and ICAM-1 at the HUVEC surface, but not tissue factor activity, whereas normal, control serum and patient serum at remission were without any effect. A close relationship between the vasculitis and the serum level of the monoclonal IgG was observed. We suggest that the monoclonal IgG might induce the vasculitis by increasing the expression of E-selectin, VCAM-1 and ICAM-1 which facilitate the interaction of leukocytes with vascular endothelium.

[Treatment of polycythemia. I--Using radiophosphorus with or without treatment in 483 patients over 65 years of age]. / Traitement des polyglobulies. I--Utilisation du radiophosphore avec ou sans traitement d'entretien chez 483 malades âgés du plus de 65 ans.

AIMS: To compare by a prospective study in high risk polycythemia vera (PV) patients 33P alone and 32P followed by low-dose hydroxyurea (HU) maintenance therapy. Toxicity, efficiency, and leukemogenic potential were studied. PATIENTS: 483 patients with a documented PV, aged more than 65 years at diagnosis, were included between 1980 and 1996 in a prospective study comparing 32P alone and 32P followed by low-dose HU maintenance therapy. Blood cell counts were performed every two months and a clinical evaluation by a specialist was obtained every four or six months. RESULTS: Treatments were well tolerated, but chronic leg ulcers were observed in the maintenance therapy arm. The risk of leukemia was about 15% at the 15th year in the group of patients treated by 32P alone, but reached 30% in the group receiving maintenance therapy. In both arms, there was no significant correlation between occurrence of leukemia and the total dose of 32P. There was a correlation between the leukemic risk and disease severity, estimated on the frequency of relapse. Cancer occurrence was slightly higher than expected in the maintenance arm. HU treatment did not protect against progression to myelofibrosis, probably due to the lack of maintenance of an efficient myeloid or megakaryocytic suppression. Median life-span was slightly shorter in the group receiving HU maintenance. In all cases, life-span was only one year lower than that observed in the reference population. CONCLUSION: For all these reasons, we suggest the us of 32P alone in elderly patients; complementary chemotherapy should only be prescribed in the cases with short-term relapse, and late resistance to 32P.

Nonproteolytic activation of the thrombin receptor promotes human umbilical vein endothelial cell growth but not intracellular CA2+, prostacyclin, or permeability.

Both thrombin and the synthetic tetracapeptide thrombin receptor-activating peptide (TRAP), recently described as a peptide mimicking the new amino terminus created by cleavage of the thrombin receptor, stimulated the proliferation of human umbilical vein endothelial cells (HUVEC) in culture. Although to a lesser extent, F-14, a tetradecapeptide representing the residues 365-378 of human prothrombin, also promoted HUVEC growth, thereby demonstrating that thrombin can stimulate HUVEC growth via both a proteolytic and a nonenzymatic pathway. Thrombin-TRAP, and F-14-induced HUVEC growth were inhibited by a thrombin receptor oligodeoxynucleotide antisense, showing that the growth-inducing effects of all 3 compounds were mediated through the same thrombin receptor. Thrombin and TRAP also stimulated intracellular Ca2+ increase, monolayer permeability increase, and prostacyclin release in HUVEC. None of these effects was observed with F-14 suggesting that thrombin-induced intracellular Ca2+ release, permeability increase, and prostacyclin release in HUVEC required catalytic cleavage of the receptor, whereas thrombin-induced growth might also be due to activation of the thrombin receptor through a nonproteolytic pathway.

[Antithrombotic agents and diabetes. Benefits and recommendations for use]. / Antithrombotiques et diabète. Bénéfices et précautions d'emploi.

Diabetic patients (3% of the French population) have a higher risk of coronary and peripheral vascular disease than non-diabetic subjects and develop long-term microvascular renal and retinal complications. Abnormalities of coagulation, haemostasis and fibrinolysis have been demonstrated in diabetics and contribute to these complications. The prescription of antithrombotics is therefore common in these patients. Platelet antiaggregants (aspirin and ticlopidine) are effective in primary and secondary prevention in reducing the overall number of vascular events (reduction of 17% in the last ATC meta-analysis) and of coronary and cerebrovascular complications in particular. Two studies have shown a preventive effect of antiaggregants on diabetic retinopathy in its initial stages. With regards to the value of the use of these agents, there are few complications which may be limited by appropriate measures. One problem lies in the choice of aspirin dosage, most studies having been performed with high doses ranging from 500 to 1,300 mg per 24 hours. It is therefore difficult to recommend doses less than 300 to 500 mg per 24 hours. The prescription of anticoagulants (heparin, vitamin-K antagonists) is not associated with more problems in diabetics than in non-diabetics. The same applies to the use of thrombolytics in the acute phase of myocardial infarction: the risk of haemorrhages, especially intraocular, is only theoretical, only one case (regressive) having been reported to date. In conclusion, diabetes is more a priviledged indication than a contra-indication to the use of antithrombotic, platelet inhibitor, anticoagulant and thrombolytic agents.

Treatment strategies in essential thrombocythemia. A critical appraisal of various experiences in different centers.

The therapeutic strategy in patients with Essential Thrombocythemia (ET) is a difficult balance between the prevention of bleeding and thrombotic complications and the risks of drug side effects and toxicity. Major bleeding is rare and seem to be related to higher platelet counts: therefore, a platelet count over 1500 x 10(9)/L is generally regarded as an indication for cytoreduction. Thrombotic complications include microvascular occlusive symptoms, which are reversible with low-dose aspirin, and large vessels thrombosis. The risk of major thrombosis is higher in ET patients aged more than 60 ys. and with previous occlusive event. In this high-risk group, the non-alkylating agent hydroxyurea (HU) significantly reduces the rate of vascular complications and has emerged as the treatment of choice. However, the long-term risk/benefit of HU remains disputed because its leukemogenic potential has not been ruled out. This holds also for other myelosuppressive agents, such as busulphan and pipobroman. Other drugs of particular interest for young patients include recombinant alpha-interferon (IFN) and Anagrelide. Both of them are effective in lowering platelet count, but their efficacy in reducing clinical complications remains to be demonstrated. However, both IFN and Anagrelide have shown to have frequent and clinically important side effects. Thus, further clinical studies are required to establish their role in the strategy of ET patient treatment.

Severe arterial thrombosis in a congenitally factor VII deficient patient.

We report a patient with congenital factor VII deficiency who developed severe arterial thrombosis. A 63-year-old-woman presented low factor VII clotting activity, amidolytic activity and antigen level < 4%. Activated factor VII plasmatic level was < 0.03 ng/ml compared to 4 ng/ml for the control value. She developed severe aorto-iliac thrombosis. 7 d before the thrombotic event, factor VII replacement therapy had been infused. Successful low molecular weight heparin therapy led to total disappearance of the aorto-iliac thrombus without bleeding complications. This suggests that factor VII infusion might have a thrombogenic effect in vivo and might be responsible for thrombosis.

The Ser 460 to Pro substitution of the protein S alpha (PROS1) gene is a frequent mutation associated with free protein S (type IIa) deficiency.

A Ser 460 to Pro mutation of protein S (PS), involving a T to C transition in exon XIII of the protein S alpha (PROS1) gene and known as the Heerlen polymorphism, was found in 16 of 85 symptomatic patients with PS deficiency (18.8%) and only 1 of 113 healthy subjects (0.8%). Another frequent polymorphism was described in exon XV of the PROS1 gene, in the codon for Pro 626 (CCA/CCG). We found that Heerlen polymorphism was associated with allele CCA and not with allele CCG, suggesting a probable transmission by a common ancestor. Most subjects bearing the Ser 460 to Pro mutation were deficient in free PS, but had normal total PS levels. Normal levels of the C4b-binding protein (C4b-BP) isoform containing a beta chain (C4b-BP beta +) ruled out increased C4b-BP beta + as a cause of the free-PS deficiency. The binding curves of the mutated (Heerlen) PS on C4b-BP immobilized on microplates were biphasic, suggesting that one molecule of C4b-BP can bind two molecules of Heerlen PS. Because normal PS binds to C4b-BP with 1:1 stoichiometry, this may explain the free-PS deficiency observed in patients carrying the Ser 460 to Pro mutation.

Increased proliferation of bone marrow-derived fibroblasts in primitive hypertrophic osteoarthropathy with severe myelofibrosis.

Pachydermoperiostosis or primary hypertrophic osteoarthropathy (HOA) is a rare congenital growth disorder of connective tissue. We report a case of severe myelofibrosis in a patient with HOA. When cultured in vitro, patient bone marrow-derived fibroblasts displayed a high proliferative potential with a shortened doubling time (24 hours v 36 to 48 hours for normal fibroblasts). The role of platelet-derived growth factor (PDGF), previously implicated in the pathogenesis of secondary acquired myelofibrosis, was studied. HOA fibroblasts expressed an increased number of PDGF-BB binding sites (300,000 sites/cell v 200,000 sites/cell for normal fibroblasts) without any modification of affinity. The increased expression of PDGF-R beta appeared to result from an accelerated rate of PDGF-R beta resynthesis with normal kinetics of endocytosis. As a consequence, a several-fold increase of PDGF-R beta tyrosine kinase activity was observed. No autocrine mechanism of growth was suspected as neither spontaneous PDGF-R beta autophosphorylation nor mitogenic activity in HOA fibroblast-conditioned medium was detected. Patient serum and platelet lysate were less potent than controls in inducing [3H]thymidine incorporation into HOA fibroblasts. This was inconsistent with a paracrine mechanism of growth. In vitro, human serum or PDGF-BB were not more mitogenic for HOA than normal fibroblasts. High levels of cyclin D1, a putative oncogene, were detected in serum-deprived HOA fibroblasts. Cyclin D1 overexpression could be implicated in the accelerated growth of these cells. Our results suggest that the mechanism of fibroblastic proliferation observed in this case of myelofibrosis might differ from those reported in other acquired myeloproliferative syndromes and could be associated with an intrinsic abnormality of HOA fibroblast growth.

Thrombin induces endothelial cell growth via both a proteolytic and a non-proteolytic pathway.

Binding of 125I-thrombin to human umbilical vein endothelial cells (HUVECs) was specifically displaced by the synthetic tetradecapeptide SFLLRNPNDKYEPF, named thrombin receptor agonist peptide (TRAP), which has recently been described as a peptide mimicking the new N-terminus created by cleavage of the thrombin receptor, and F-14, a tetradecapeptide representing residues 365-378 of the human alpha-thrombin B chain. Binding of 125I-TRAP to HUVECs was time-dependent, reversible and saturable, showing high affinity (KD = 1.5 +/- 0.4 microM) and high binding capacity (Bmax. = 7.1 +/- 0.6 x 10(6) sites/cell) (n = 3). Unlabelled thrombin and TRAP competitively and selectively inhibited the specific binding of 125I-TRAP with IC50 values of 5.8 +/- 0.7 nM and 2.8 +/- 0.4 microM respectively, whereas F-14 remained ineffective at displacing 125I-TRAP from its binding sites, suggesting the presence of at least two different types of thrombin-binding sites on HUVECs. TRAP was a potent mitogen for HUVECs in culture. Both TRAP and alpha-thrombin stimulated the proliferation of HUVECs with half-maximum mitogenic responses between 1 and 10 nM. F-14 also promoted HUVEC growth. The mitogenic effects of F-14 and TRAP were additive. N alpha-(2-Naphthylsulphonylglycyl)-DL-p-amidinophenylalanylpiper idine (NAPAP) and hirudin (two specific inhibitors of the enzyme activity of thrombin) specifically inhibited thrombin-induced HUVEC growth (IC50 values 400 +/- 60 and 52 +/- 8 nM respectively) but remained without effect on the mitogenic effect of TRAP or F-14. This demonstrated that the mitogenic effect of alpha-thrombin for HUVECs was intimately linked to its esterolytic activity but also showed that thrombin can stimulate HUVEC growth via another non-enzymic pathway. This hypothesis was further reinforced by the fact that F-14-induced proliferation of HUVECs remained unaltered by two antibodies directed against TRAP or the cleavage site on the extracellular portion of the thrombin receptor, which both strongly reduced thrombin-induced proliferation of HUVECs. Thrombin-, TRAP- or F-14-induced HUVEC proliferation was strongly inhibited by a neutralizing monoclonal antibody directed against basic fibroblast growth factor (bFGF), suggesting that thrombin regulates the autocrine release of bFGF in HUVECs.

Five novel mutations located in exons III and IX of the protein C gene in patients presenting with defective protein C anticoagulant activity.

We describe five families presenting with type II hereditary protein C deficiency characterized by normal antigen and amidolytic activity levels but low anticoagulant activity. All the exons and intron/exon junctions of the protein C gene were studied using a strategy combining amplification by the polymerase chain reaction (PCR), denaturing gradient gel electrophoresis of the amplified fragments, and direct sequencing of fragments displaying altered melting behavior. We detected five novel mutations. Three were located in the C-terminal part of the propeptide encoded by exon III: Arginine (Arg)-5 to tryptophan (Trp), Arg-1 to histidine (His), and Arg-1 to cysteine (Cys) mutations. The two others, located in exon IX, affected Arg 229 and serine (Ser) 252, which were respectively replaced by glutamine (Gln) and asparagine (Asn). DNA studies of the other exons from affected individuals showed no other abnormalities. These novel mutations provide further insight into the importance of the affected amino acids located close to the active site, near Asp 257, one of the three amino acids of the catalytic triad. The low anticoagulant activity of the abnormal protein C indicated that Arg 229 and Ser 252 play a key role during the interaction between protein C and its cofactor protein S, phospholipids, or factors Va and VIIIa. The Arg-1 to Cys mutation led to the dimerization of protein C with another plasmatic component, as evidenced by the presence in the plasma of a high molecular weight form of protein C that disappeared after reduction. No molecular mass abnormalities were observed in heavy and light chains of all other protein C mutants. In the five families explored, 9 (64%) of the 14 subjects bearing the mutations reported thrombotic events. This suggests that the protein C amino acids affected by the mutations are very important for the in vivo expression of the antithrombotic properties of protein C.