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N Schlegel

Publications and source records attributed to N Schlegel.

At least 19 recordsLinked to original sources
PubMed2005

Effects of root replantation and neurotrophic factor treatment on long-term motoneuron survival and axonal regeneration after C7 spinal root avulsion.

In order to determine the effect of nerve root replantation on motoneuron survival and regeneration, we have avulsed and replanted C7 ventral rootlets in adult rabbits under various conditions. Intraspinal alterations and exact positions of ventrolateral replantations were studied in each animal, and the effects of BDNF and/or CNTF administration during replantation investigated in different experimental groups. Six months after lesion, about 70% of motoneurons were lost on the lesioned sides in the C7 segment, without significant differences between groups. Retrograde fluorescent tracing and histological analysis documented that many axons had regrown through the original ventral exit zones or had exited the spinal cord at the lateral replantation site. However, many laterally exiting axons had not grown out directly from the ventral horn through the lateral white matter but had elongated vertically before leaving the spinal cord. The mean axonal diameter was significantly higher in regenerated axons that had exited through the original ventral exit zones in comparison with axons which had grown out laterally. Application of BDNF and/or CNTF did not show any effects on the pathways of regeneration into the replanted root. The results indicate that motoneuron survival cannot be significantly improved by a single dose of neurotrophic factors applied to a ventrolateral replantation site. However, a significant number of myelinating axons are found in replanted roots, and regeneration may be more efficient when outgrowth through the original ventral exit zone is supported.

Animals↗
PubMed2001

Probing conformational changes in the I-like domain and the cysteine-rich repeat of human beta 3 integrins following disulfide bond disruption by cysteine mutations: identification of cysteine 598 involved in alphaIIbbeta3 activation.

We have investigated receptor function and epitope expression of recombinant alpha(IIb)beta(3) mutated at Cys(177) or Cys(273) in the I-like domain as well as Cys(598), located in the fourth repeat of the membrane-proximal cysteine-rich region and mutated in a Glanzmann's thrombasthenia type II patient. The beta(3) mutants beta(3)C177A, beta(3)C273A, and beta(3)C598Y exhibited a decreased electrophoretic mobility in SDS-polyacrylamide gel electrophoresis under nonreducing conditions, confirming the disruption of the respective disulfide loops. Despite reduced surface expression, the alpha(IIb)beta(3)C177A, alpha(IIb)beta(3)C273A, and alpha(IIb)beta(3)C598Y receptors mediated cell adhesion to immobilized fibrinogen and translocated into focal adhesion plaques. The beta(3)C598Y mutation, but not the beta(3)C177A or beta(3)C273A mutations, induced spontaneous binding of the ligand mimetic monoclonal antibody PAC-1, while the beta(3)C177A and beta(3)C273A mutants exhibited reduced complex stability in the absence of Ca(2+). Epitope mapping of function-blocking monoclonal antibodies (mAbs) allowed the identification of two distinct subgroups; mAbs A2A9, pl2-46, 10E5, and P256 did not interact with alpha(IIb)beta(3)C273A and bound only weakly to alpha(IIb)beta(3)C177A, while mAbs AP2, LM609 and 7E3 bound normally to mutant alpha(IIb)beta(3)C273A, but interacted only weakly with mutant alpha(IIb)beta(3)C177A. Furthermore, a cryptic epitope recognized by mAb 4D10G3 and not exposed on wild type alpha(IIb)beta(3) became accessible only on mutant alpha(IIb)beta(3)C177A and was mapped to the 60-kDa chymotrypsin fragment of beta(3). Finally, the ligand-induced binding site (LIBS) epitopes AP5, D3, LIBS1, and LIBS2 were spontaneously expressed on all three mutants independent of RGDS or dithiothreitol treatment. Our results provide evidence that disruption of a single cysteine disulfide bond in the cysteine-rich repeat domain, but not in the I-like domain, activates integrin alpha(IIb)beta(3). In contrast, disruption of each of the disulfide bonds in the two long insertions of the I-like domain predicted to be in close contact with the alpha subunit beta-propeller domain affect the stability of the alpha(IIb)beta(3) heterodimer and inhibit complex-specific mAb binding without affecting the RGD binding capacity of the metal ion-dependent adhesion site-like domain.

Animals↗
PubMed2001

[Meningococcal purpura fulminans: untoward result of genetic polymorphism?].

Despite significant progress in intensive care medicine, the mortality of septic shock has not changed in recent years. Early recognition of subtle signs in favor of meningococcal sepsis, early antibiotic treatment, and aggressive hemodynamic support remains the cornerstone of therapy of severe meningococcal shock in children. Recent work has emphasized the role of genetic polymorphisms in various systems to explain the most severe cases: anti-inflammatory cytokine profile IL-10/TNF-alpha, elevated levels of plasminogen activator inhibitor type-1, variants of the gene for mannose-binding lectin complement pathway. This may explain the disillusionment of pediatric intensivists, and the general failure of immunotherapy for sepsis. Reasonable hope lies upon new meningococcal vaccines.

Child↗
PubMed2001

Thromboembolism in newborns, infants and children.

As in adults, acquired and inherited prothrombotic risk factors increase the risk of thrombosis in neonates, infants and children. Duplex sonography, venography, computed tomography and magnetic resonance imaging can be used to diagnose childhood thromboembolism, but venography is the recommended method to confirm vascular occlusion of the upper venous system. After suffering thrombosis, patients should be screened for factor V G1691A, prothrombin G20210A and MTHFR C677T genotypes, deficiencies of protein C, protein S, and antithrombin, elevation of lipoprotein (a) and fasting homocysteine concentrations (3 to 6 months after thrombotic onset: plasma-based assays). Data interpretation is based on age-dependent reference ranges and the identification of causative gene mutations/polymorphisms with respect to the individual ethnic background. Paediatric treatment protocols for acute thromboembolism, including thrombolytic and anticoagulant therapy, are hampered by the lack of appropriate clinical trials. Thus, recommendations from small-scale studies in paediatric patients and guidelines adapted from adult patient protocols may be helpful in the management of paediatric patients on an individual patient basis.

Anticoagulants↗
PubMed2001

[Extracorporeal lithotripsy in the treatment of salivary lithiasis. A prospective study apropos of 27 cases].

In a prospective study, we evaluated the efficacy of extracorporeal lithotripsy (ECL) in the treatment of salivary stones. We define the indications for the treatment of submaxillary and parotid stones, depending on the diameter and the location of the stone. Twenty-seven patients were treated by ECL. All had a unique stone, in the salivary duct, with a diameter greater than 2 mm; the site was the parotid gland for ten cases, the submaxillary gland for seventeen cases. After six months, the results from a clinical and ultrasonography point of view, were the following: total efficacy or complete desintegration of the stone: 9 cases; partial efficacy or fragmentation of the calculi, with residual fragments with a diameter of less than 2 mm, which could be flushed out with possible spontaneous clearance: 10 cases; failure or the lack of the reduction in the size of the stone or partial fragmentation into concrements with a diameter of more than 2 mm: 8 cases. Based on our experience and the results reported in the medical literature, we propose an therapeutic approach to symptomatic salivary stones. ECL is the most preferable treatment for stones of the parotid duct or parotid gland. The treatment of stones of the submaxillary gland depends on the site and the size of the calculi; ECL should be proposed as first-line treatment when the stone diameter ranges from 2 to 10 mm and when it is situated in the pelvis of the duct or in the proximal duct; surgical resection of the submandibular gland is indicated when the stone is situated in the gland itself or when the diameter is more than 10 mm; when it is situated in the distal duct, a marsupialization should be performed.

Adolescent↗
PubMed2000

Effect of individual plasma lipoprotein(a) variations in vivo on its competition with plasminogen for fibrin and cell binding: An in vitro study using plasma from children with idiopathic nephrotic syndrome.

Simultaneous natural changes in lipoprotein(a) [Lp(a)] and plasminogen occur in the nephrotic syndrome and offer a unique opportunity to investigate their effects on plasminogen activation under conditions fashioned in vivo. Plasminogen, Lp(a), and apolipoprotein(a) in plasma were characterized, and their competitive binding to carboxy-terminal lysine residues of fibrin and cell membrane proteins was determined in nephrotic children during a flare-up of the disease (61 cases) and after 6 weeks (33 cases) and 6 months (42 cases) of remission. Low plasminogen concentrations (median 1.34 micromol/L, range 0.39 to 1.96 micromol/L) and high Lp(a) levels (median 0.27 g/L, range 0.07 to 2. 57 g/L) were detected at flare-up. These changes were associated with an increased Lp(a) binding ratio onto fibrin (3.13+/-0.48) and cells (1.53+/-0.24) compared with binding ratios of control children (1.31+/-0.19 and 1.05+/-0.07, respectively) with normal plasminogen and low Lp(a) (median 0.071 g/L). After 6 weeks and 6 months of remission, the values for net decrease in Lp(a) binding to fibrin were 1.7+/-0.22 (after 6 weeks) and 1.88+/-0.38 (after 6 months) and were correlated with low Lp(a) concentrations (median 0.2 g/L, range 0.07 to 0.8 g/L; and median 0.12 g/L, range 0.07 to 1.34 g/L) and inversely associated with increased plasminogen levels (median 1.82 micromol/L, range 1.4 to 2.1 micromol/L; and median 1.58 micromol/L, range 1.1 to 2.1 micromol/L). These studies provide the first quantitative evidence that binding of Lp(a) to lysine residues of fibrin and cell surfaces is directly related to circulating levels of both plasminogen and Lp(a) and that these glycoproteins may interact as competitive ligands for these biological surfaces in vivo. This mechanism may be of relevance to the atherothrombotic role of Lp(a), particularly in nephrotic patients.

Adolescent↗
PubMed1999

Intermittent hemophagocytic lymphohistiocytosis is a regular feature of lysinuric protein intolerance.

We describe 4 cases of lysinuric protein intolerance, which all fulfilled the diagnostic criteria for hemophagocytic lymphohistiocytosis. Mature histiocytes and neutrophil precursors participated in hemophagocytosis in the bone marrow. Moreover, serum levels of ferritin and lactate dehydrogenase were elevated, hypercytokinemia was present, and soluble interleukin-2 receptor levels were increased up to 18.6-fold. The diagnosis of lysinuric protein intolerance should therefore be considered in any patient presenting with hemophagocytic lymphohistiocytosis.

Amino Acid Metabolism, Inborn Errors↗
PubMed1999

Thrombolysis in newborns and infants.

This review analyses literature reports from 1970 to 1998 assessing the use of streptokinase (SK), urokinase (UK) or recombinant tissue-type plasminogen activator (rt-PA) for thrombolytic therapy in neonates and infants. From 1970 to 1998 182 infants were reported to have received SK (n = 54; 29.5%), UK (n = 41; 22.5%) or rt-PA (n = 87; 48%). During thrombolytic therapy no concomitant heparin administration or low dose heparin therapy (5 U/kg/h) were recorded. To perform reocclusion prophylactics heparin was reinitiated at the end of thrombolytic therapy usually in the recommended dosage of 20 U/ kg/h. The overall thrombolytic patency rate in neonates varied from 39% to 86%. Besides bleeding from local puncture sites or recent catheterisation sites (10.4%), pulmonary embolism was reported in 1.1% of the 182 infants. Major bleeding complications, i.e. pulmonary bleeding (0.6%), gastrointestinal bleeding (0.6%) or intraventricular haemorrhage (IVH 2.7%) are rarely reported side effects and only 2 thrombolysis related deaths due to haemorrhage were mentioned. Bleedings reported in the central nervous system (n = 4) mainly occurred in preterm infants (n = 3). In conclusion, data of this preliminary analysis suggest that there is no big difference (p = 0.09; chi2-test) in the efficacy rate between the 3 thrombolytic agents used in the first year of life. In each case an assessment must be made with respect to the relative benefit conferred by thrombolytic therapy in preventing organ or limb damage versus the potential side effects, costs and inconvenience for the childhood patient. Controlled prospective multicentre studies on thrombolytic therapy in neonates and infants are recommended to evaluate patency rates and adverse effects for the different thrombolytic agents used.

Child, Preschool↗
PubMed1997

Frequency of immune thrombocytopenia in newborns: a prospective study. Immune Thrombocytopenia Working Group.

Thrombocytopenia is a common condition in distressed newborns, but little is known about thrombocytopenia in an unselected cohort of neonates. In an attempt to address this issue, a multicenter prospective study was conducted in three obstetrical wards of AP-HP in Paris. We found the frequency of neonatal thrombocytopenia (<150 x 10(9)/L) to approximate 0.9% (48 of 5,632 appropriate samples). An immune mechanism was likely to be the cause of thrombocytopenia in 10 of the 33 cases studied, implying an incidence of 0.3% of immune neonatal thrombocytopenia in the general population. The frequency of alloimmune thrombocytopenia was 1.5/1,000 liveborn neonates, and 1/1,000 when considering anti-HPA-1a allo-immunization. Because thrombocytopenia, whatever its cause, was often silent and delayed, it appears that the only way to detect neonatal thrombocytopenia in time to prevent its potential disastrous complications would be to perform a systematic neonatal blood sampling for platelet count. All cases of ascertained thrombocytopenia should then be screened for an immune mechanism to enable early detection of autoimmune diseases in mothers and careful monitoring of subsequent pregnancies and deliveries, leading to appropriate prevention of potential severe deleterious effects in the offspring.

Adult↗
PubMed1997

Platelet factor 4 and other CXC chemokines support the survival of normal hematopoietic cells and reduce the chemosensitivity of cells to cytotoxic agents.

The effects of platelet factor 4 (PF4) on the viability and chemosensitivity of normal hematopoietic cells and cancer cell lines were studied to determine the mechanisms whereby PF4 functions as either an inhibitor or a protector and to evaluate its clinical significance. Two other chemokines, interleukin-8 (IL-8) and neutrophil-activating peptide-2 (NAP-2), were also studied in comparison to PF4. Using a tetrazolium salt assay for cell viability, we observed that PF4 at 1 to 50 microg/mL supported the viability of normal human bone marrow cells. Approximately 45% of cells cultured for 48 hours survived, whereas 80% or more survived in the presence of PF4 5 microg/mL. PF4 also supported the viability of CD34+ cord blood (CB) cells and protected them from apoptosis induced by transforming growth factor beta1 (TGFbeta1) and cytotoxic drugs. Pretreatment of CD34+ cells by PF4, but not by TGFbeta1, caused an increase in the number of megakaryocyte colonies after these cells were replated in secondary cultures. Flow cytometry analysis showed that when CD34+ cells were preincubated with PF4 or TGFbeta1 for 12 days in hematopoietic growth factor-rich medium, an increased number of remaining CD34+ cells was observed only for PF4-treated cells. Furthermore, PF4 significantly reduced the chemosensitivity of bone marrow cells, as shown by its ability to increase the 50% inhibition concentration (IC50) of several cytotoxic agents. Like PF4, IL-8 and NAP-2 at 0.1, 0.6, and 1 microg/mL supported the survival of myeloid progenitors, including colony-forming units granulocyte, erythroblast, monocyte, megakaryocyte (CFU-GEMM), CFU-megakaryocyte (CFU-MK), CFU-granulocyte/macrophage (CFU-GM), and burst-forming units-erythroblast (BFU-E), and reduced their sensitivity to the toxicity of etoposide (ETP). Protamine sulfate at 1 to 100 microg/mL showed no such activity of PF4. Interestingly, the three chemokines failed to affect significantly the viability and chemosensitivity of three leukemic and two other tumor cell lines. Based on these results, we conclude for the first time that PF4 and IL-8 and NAP-2 support the survival of normal hematopoietic precursors and protect them from the toxicity of chemotherapeutic agents. Because such activities are unique to normal hematopoietic cells but not to the cancer cell lines evaluated, a potential clinical application of these molecules in the treatment of cancer is suggested.

Apoptosis↗
PubMed1997

Expansion of polyclonal B-cell precursors in bone marrow from children treated for acute lymphoblastic leukemia.

In a series of 12 patients (mean age: 3 years at diagnosis) receiving chemotherapy for acute lymphoblastic leukemia, bone marrow examinations performed during hematopoietic recovery following treatment-induced agranulocytosis or completion of maintenance treatment showed at least 15% of non malignant immature cells which were sometimes hardly distinguishable from leukemic cells. No comparable data was observed in patients treated with G-CSF. The cytological features of these cells as well as their immunophenotyping were defined. Results showed that the majority of cells expressed HLA-DR, CD19, CD10 and cytoplasmic IgM but not the CD34 markers. This predominant and homogeneous pre-B cell population which likely represents the expansion of a minor population detectable in normal bone marrow is phenotypically indistinguishable from leukemic cells. The pattern of IgH gene rearrangements studied by PCR amplification of the CDRIII region showed that these cells were polyclonal. Except in one patient, minimal residual disease was not detected using probes specific for IgH or TCR gene rearrangement of the malignant clone. In children during the hematopoietic recovery after chemotherapy, immature marrow cells in great numbers, even with an highly homogeneous immunophenotype identical to the malignant clone's, are not sufficient for the diagnosis of relapse.

Antigens, Surface↗
PubMed1997

[Transgenic human thymopoiesis from retrovirally transduced umbilical cord blood hematopoietic stem cells: experimental studies in the SCID-hu mouse].

The gene encoding the CD2 mouse cell surface antigen was retrovirally transduced into cord blood CD34+ cells. On infection by culture at the contact of retrovirus-packaging cells, the mCD2 marker was expressed by 30-40% CD34+ cells, that included the most primitive stem cell-enriched Thy-1+ and CD38- subsets. Accordingly, sorted cord blood CD34+Thy-1+ cells could be directly infected in the same conditions. mCD2- transgenic cord blood CD34+ cells were then used to reconstitute human fetal thymus implanted in SCID mice. Five to 8 weeks later, the mCD2 antigen was detected on approximately 10% of the human thymocytes repopulating the thymus grafts and the transgene genome was detected in graft cell DNA by Southern blot. These results demonstrate efficient gene transfer into primitive cord blood hematopoietic cells endowed with lymphoid potential and suggest gene therapy schemes in neonates suffering inherited or acquired-such as HIV infection-disorders of the T-cell lineage.

Animals↗
PubMed1997

Thromboembolic risks and complications in nephrotic children.

The identification of many biologic anomalies is progressively realized in nephrotic children, thanks to adult studies and to scientific advances. The number of anomalies and the intensity of alterations vary from one patient to another and during flare-ups in the same patient. Their severity is usually a function of the severity of the nephrotic syndrome (NS). The responsibility of each anomaly per se in triggering thrombotic complications is not yet known and today it is understood that the coexistence of several factors is necessary to induce these complications. Thus, the NS presents a true model because it can gather multiple thrombogenic anomalies. It might be more satisfying to characterize all of the mechanisms that could be responsible for a thrombosis rather than to assay all of the biologic components in one patient. When the main balances during the childhood NS are broken-pro- versus anticoagulant forces, pro- versus antifibrinolytic forces, platelet/vessel wall interactions-one cannot evaluate with accuracy the possible impact of acquired interrelations such as a decrease of antithrombin versus an increase of protein C. Among the present unknown factors, a major one is related to the effects, if any, of the proteinuric factor (recently discovered) on the vascular endothelium and the central question is: would it be capable of changing the thromboresistant phenotype to a thrombogenic one? No absolute correlation has been found between the many biologic abnormalities and the occurrence of thromboembolic (TE) complications. However, it is of great interest to have the best evaluation of the TE risks in nephrotic children. The criteria that are commonly used are: albuminuria, and plasma levels of fibrinogen and antithrombin. One can suggest adding to these criteria the D-dimer assay, a molecular marker of coagulation activation, and the factor V Leiden workup because it represents a genetic predisposition for TE complications. As far as prevention of TE complications is concerned, the standard but basic guidelines of nephrotic patients must be followed. Furthermore, vitamin K antagonists should be administered as soon as the risk criteria are gathered, but only after a careful evaluation of the benefits/risks ratio. As to the treatment of TE events, one should follow the present recommendations for children. A better future regarding prevention of TE accidents is based not only on the necessity of multicentric prospective studies but also on basic research that will allow discovery of the "primum movens" of childhood NS.

Blood Coagulation Disorders↗
PubMed1996

A cell surface marker gene transferred with a retroviral vector into CD34+ cord blood cells is expressed by their T-cell progeny in the SCID-hu thymus.

Gene transduction into immature hematopoietic cells collected at birth from the umbilical cord could be useful for the treatment of genetic or acquired disorders of the hematopoietic system diagnosed during pregnancy. The SCID-hu mouse is a convenient model to investigate T-cell lineage gene therapy, since it allows replication of human intrathymic T-cell development. CD34+ cells isolated from cord blood were cocultured with CRIP MFG-murine CD2 (mCD2) cells that produce recombinant retroviruses encoding the mCD2 antigen, a cell surface marker easily detectable by flow cytometry. After 3 and 4 days in coculture, a mean of 19% and 39% human hematopoietic cells, respectively, expressed the mCD2 antigen. CD34+ cells cocultured for 4 days were used to reconstitute human fetal thymus implanted in SCID mice. Five to 10 weeks later, the mCD2 antigen was detected on approximately 10% of human thymocytes repopulating the thymic grafts in four of nine SCID mouse chimeras. Vector genomes were detected in graft cell DNA by Southern blot. Analysis of vector integration indicated that positive cells were of polyclonal origin in three animals and predominantly monoclonal in the other one. Our data show that foreign genes can be transduced into CD34+ cord blood cells endowed with T-cell differentiation potential, and suggest strategies for T-cell lineage gene therapy in the neonate.

Animals↗
PubMed1996

[Lysinuric dibasic protein intolerance: characteristic aspects of bone marrow involvement].

BACKGROUND: The marrows of patients with lysinuric protein intolerance (LPI) are generally considered as normal, even though autoerythrophagocytosis has been observed in some of them. CASE REPORTS: Lysinuric protein intolerance was recognized in two 12 and 15-year-old brothers who had been diagnosed following an immuno-hematological investigation. Clinical history had been characterized by a neonatal macrophage activation syndrome (hepatosplenomegaly, pancytopenia, hypofibrinogenemia and hypertriglyceridemia). A putative diagnosis of familial lymphohistiocytosis had been ruled out because of unusual clinical and immunological course. Both brothers had displayed chronic aversion to high-protein foods, failure to thrive, osteoporosis and developmental delay. Metabolic investigations had revealed chronic hyperammonemia while cationic aminoaciduria (lysine, arginine and ornithine) was only present during L-citrulline supplementation. Bone marrow examinations had been performed during the neonatal period and during later metabolic investigations. They both displayed a peculiar red cell and granulocytes phagocytosis by histiocytes and granulocytes precursors. CONCLUSIONS: This aspect of bone marrow could be considered as a specific sign of LPI. This report suggests that appropriate metabolic investigations should be performed in any unexplained macrophage activation syndrome.

Amino Acid Metabolism, Inborn Errors↗
PubMed1996

Isolated X-linked thrombocytopenia in two unrelated families is associated with point mutations in the Wiskott-Aldrich syndrome protein gene.

The Wiskott-Aldrich syndrome (WAS) is characterized by defective platelet and lymphocyte function associated with eczema and increased susceptibility to malignancies. It is caused by mutations of the WAS protein-encoding gene (WASP). X-lined thrombocytopenia, defined by low platelet counts and volume, may be an allelic variant of WAS. In patients with XLT from two unrelated families, WASP gene defects were identified by single-strand conformational polymorphism and by sequencing. Point mutations in exon 2 of the WASP gene were found in the patients from both families in which XLT segregated. Several obligate heterozygote female members of these families display a random pattern of X inactivation in their peripheral blood leukocytes. This study shows that XLT may be caused by mutations of the WASP, thus representing an allelic variant of WAS.

Adult↗