Biomedical subjects

C Bührer

Publications and source records attributed to C Bührer.

At least 55 records · Page 3Linked to original sources

PubMed1996

CD45 engagement induces L-selectin down-regulation.

The CD45 glycoprotein isoforms exhibit a receptor-like composition and display intracellular protein tyrosine phosphatase (PTPase) activity. The present study links CD45 to the regulation of L-selectin (CD62L), a leucocyte glycoprotein important for extravasation and homotypic aggregation. Monoclonal antibodies (MoAbs) IOL1b and AICD45.2, but not GAP8.3, all of which are directed against common CD45 epitopes, were found to elicit lymphocyte L-selectin down-regulation. Lymphocyte L-selectin down-regulation in response to anti-CD45 MoAbs was enhanced by high cell density and partially antagonized by the protein tyrosine kinase (PTK) inhibitor, herbimycin A. The MoAbs IOL1b, AICD45.2 and GAP8.3 recognized granulocyte-expressed CD45 but did not induce loss of L-selectin expression of granulocytes. In contrast, the CD45 PTPase inhibitor, vanadate, induced L-selectin down-regulation both in lymphocytes and granulocytes. The PTPase activation by nitric oxide (NO) or the NO-generating compound, sodium nitroprusside, did not affect L-selectin surface expression. Increased concentrations of soluble L-selectin were detected after anti-CD45 or vanadate-induced down-regulation of L-selectin surface expression. While activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate (PMA) induces rapid L-selectin down-regulation of L-selectin surface expression in both lymphocytes and granulocytes, the PKC inhibitor, H 7, was also found to down-regulate lymphocyte and granulocyte L-selectin surface expression. The inhibitor H 7 synergized with vanadate in down-regulating lymphocyte L-selectin surface expression, but partially inhibited vanadate-induced granulocyte L-selectin down-regulation. The results suggest that in a cell type-specific fashion the PKC system and tyrosine phosphorylation and dephosphorylation cascades are involved in the regulation of L-selectin surface expression.

Adult↗

PubMed1996

Cerebrospinal fluid soluble L-selectin (sCD62L) in meningoencephalitis.

The leucocyte adhesion molecule L-selectin (CD62L) is rapidly cleaved off proteolytically after cell activation, generating soluble L-selectin (sCD62L) molecules. sCD62L concentrations were determined in 185 cerebrospinal fluid (CSF) samples obtained from children aged 1 month to 17 years. In 36 CSF samples of children with meningoencephalitis, sCD62L was significantly higher (median 209 fmol/ml) than in samples of children with other febrile diseases (n = 67, median 50 fmol/ml) or non-febrile disorders (n = 82, median 44 fmol/ml). There was a positive correlation between CSF protein and CSF sCD62L (rS = 0.68), suggesting that a disturbed blood-brain barrier contributes to raised sCD62L concentrations in the CSF. However, the CSF sCD62L/protein ratio of children with meningoencephalitis was significantly higher than in children with other febrile diseases or non-febrile disorders, indicating that sCD62L concentrations in children with meningoencephalitis were higher than expected from plasma leakage alone. It is concluded that both an impaired blood-brain barrier and the generation of sCD62L by infiltrating leucocytes contribute to raised CSF sCD62L concentrations in children with meningoencephalitis.

Acute Disease↗

PubMed1996

Peripheral blast counts at diagnosis of late isolated bone marrow relapse of childhood acute lymphoblastic leukemia predict response to salvage chemotherapy and outcome. Berlin-Frankfurt-Münster Relapse Study Group.

PURPOSE: In newly diagnosed childhood acute lymphoblastic leukemia (ALL), a high tumor burden indicates a poor prognosis, while no such link has been established yet after relapse. The impact of the absolute peripheral blast count (PBC) at the time of relapse on the response to salvage chemotherapy after a late isolated bone marrow (BM) relapse is the subject of this prospective analysis. PATIENTS AND METHODS: Since 1983, 260 children with a first isolated BM relapse of ALL that occurred 6 months or later after elective cessation of front-line therapy were enrolled onto four consecutive multicenter trials of the Berlin-Frankfurt-Münster (BFM) Relapse Study Group. All patients received intensive multiagent induction and consolidation chemotherapy for 6 months, followed by maintenance therapy with methotrexate (MTX) and thioguanine for 2 years. Treatment of subclinical meningeal leukemia consisted of high-dose intravenous MTX and intrathecally administered cytostatic drugs, which was augmented by cranial irradiation since 1988. RESULTS: At the time relapse was diagnosed, PBC varied considerably among patients (median, 1,060/microL; range, 0 to 106,800/microL). Achievement of a second complete remission (CR) was not significantly different in children without detectable circulating blasts at relapse (37 of 38) and those with moderate (1 to 9,999/microL) PBC (165 of 171). In contrast, only 42 of 51 children with high PBC (> or = 10,000/microL) achieved a second CR (P = .0015). At a median follow-up time of 40 months, the 10-year event-free survival (EFS) probability was significantly (P = .0001) higher in children without circulating blasts (.64) than in children with moderate PBC (.32) or high PBC (.10). There was a preponderance of boys in the group without detectable circulating blasts, while the three PBC-defined groups did not differ with respect to frontline treatment, age at initial diagnosis, age at relapse, time off therapy, or salvage treatment protocol. On sequential univariate and multivariate analysis, only duration of first remission > or = 48 months was an additional independent indicator of adverse prognosis, while preventive cranial irradiation improved outcome independently of PBC. CONCLUSION: The absence of blasts on peripheral-blood smears at the time of a first late isolated BM relapse of childhood ALL is associated with a favorable response and prognosis in chemotherapy-treated children, who should be regarded as ineligible for bone marrow transplantation (BMT) unless a second round of chemotherapy has failed to produce a response.

Adolescent↗

PubMed1995

Dose-response to inhaled nitric oxide in acute hypoxemic respiratory failure of newborn infants: a preliminary report.

In acute hypoxemic respiratory failure of term and near-term neonates, extra- and intrapulmonary right-to-left shunting contribute to refractory hypoxemia. Inhaled nitric oxide (NO) decreases pulmonary arterial pressure and improves ventilation-perfusion mismatch in a variety of animal models and selected human patients. We report on 10 consecutive term and near-term newborns with severe acute hypoxemic respiratory failure due to diaphragmatic hernia, meconium aspiration syndrome, group B streptococcus sepsis, pneumonia or acute respiratory distress syndrome, who received increasing doses of inhaled NO (up to 80 ppm) to improve the arterial partial pressure of oxygen (PaO2). The response to NO and the optimum NO concentration which improved PaO2 varied considerably between patients. Improvement of PaO2 was absent or poor (less than 10 mm Hg) in the 4 newborns with meconium aspiration syndrome and in 1 patient with congenital diaphragmatic hernia, while in the other 5 patients inhaled NO increased the mean (+/- SE) PaO2 from 41 +/- 6 to 57 +/- 9 mm Hg (P < 0.05). Optimum NO concentrations determined by dose-response measurements performed during the first 8 hr of NO inhalation were 8-16 ppm except for 2 newborns with congenital diaphragmatic hernia who required 32 ppm to effectively increase PaO2. Four of the 5 patients in whom the PaO2 rose by more than 10 mm Hg received inhaled NO for extended periods of time (5 to 23 days) with no signs of tachyphylaxis. The optimum NO concentration dropped to less than 3 ppm after prolonged mechanical ventilation or when intravenous prostacyclin was given concomitantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗

PubMed1995

Soluble L-selectin (sCD62L) umbilical cord plasma levels increase with gestational age.

L-Selectin (CD62L) is a leukocyte surface membrane glycoprotein involved in extravasation and homotypic aggregation which is rapidly cleaved off after cellular activation. From culture supernatants and body fluids, soluble L-selectin (sCD62L) has been recovered with its functional activity retained. We devised a sensitive enzyme-linked immunoassay for quantitation of sCD62L which was used to measure sCD62L in umbilical cord plasma of 255 human newborns with a gestational age (GA) of 23-43 wk (median 38 wk). sCD62L levels ranged from 1.14-13.8 pmol/mL (median 7.2 pmol/mL) and showed strong correlations with GA (r = 0.71, p < 0.001), birth weight (r = 0.66, p < 0.001), and absolute neutrophil cell counts (ANC) (r = 0.62, p < 0.001) obtained from a peripheral vein within the first 6 h of life (n = 153), whereas there was a weak inverse correlation with absolute normoblast counts (r = -0.27, p < 0.001). In multiple regression analysis, only GA and ANC retained a significant association with sCD62L levels (p < 0.001). Decreased sCD62L levels were found to be associated with multiple gestation (4.8 +/- 2.4 pmol/mL versus 7.7 +/- 2.3 pmol/mL, p < 0.05) also when considering GA and ANC as covariates. In contrast, increased sCD62L levels in infants born from meconium-stained amniotic fluid, and decreased levels in newborns with acute bacterial infection could be fully attributed to differences in GA and ANC.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Infections↗

PubMed1994

Importance of effective central nervous system therapy in isolated bone marrow relapse of childhood acute lymphoblastic leukemia. BFM (Berlin-Frankfurt-Münster) Relapse Study Group.

Presymptomatic central nervous system (CNS) treatment in children with a late isolated first bone marrow (BM) relapse of acute lymphoblastic leukemia (ALL) was based on intermediate-dose systemic and intrathecal (IT) methotrexate (MTX) in the multicenter trial, ALL-REZ BFM 85. Because this was associated with an excess of overt second CNS relapses, cranial radiotherapy (cRT) plus prolonged triple IT therapy with MTX, cytarabine, and prednisone was instituted during the course of the subsequent trial, ALL-REZ BFM 87. Results of children with or without cRT, but otherwise identical chemotherapy, are presented here. Between April 1985 and March 1990, 93 children with their first late isolated BM relapse of ALL were entered on protocols ALL-REZ BFM 85M and ALL-REZ BFM 87. An intensive 6-month phase of multiagent chemotherapy that included 8 courses of systemic MTX (1 g/m2) plus IT MTX was followed by 2 years of conventional maintenance therapy with daily 6-thioguanine and biweekly MTX. Children with bone marrow transplantation excluded, 73 were in complete remission at the end of intensive polychemotherapy, 40 of whom received fractionated cRT plus triple IT therapy during the following 6 months; 11 did not receive cRT but prolonged triple IT; 22 received neither cRT nor prolonged triple IT. Except for a higher percentage of children who had received cRT in front-line protocols (29 of 33 v 20 of 40), the patient groups without or with salvage cRT were comparable. Of 33 children without salvage cRT, 26 relapsed, compared with 21 of 40 who had received cRT (P < .05). The difference was solely attributable to second relapses with CNS involvement (10 of 33 v 1 of 40; P < .01). Estimated 6-year event-free survival rates were .18 for children without cRT and .46 for children with cRT (P < .01). In patients without cRT, no impact of prolonged IT therapy could be shown. The data suggest that second CNS prophylaxis with cRT and prolonged triple IT therapy in children with late isolated BM relapse of ALL is effective in preventing CNS relapses, in reducing the overall relapse rate, and in increasing the overall survival rate.

Adolescent↗

PubMed1994

L-selectin is down-regulated in umbilical cord blood granulocytes and monocytes of newborn infants with acute bacterial infection.

The leukocyte glycoprotein L-selectin mediates an early step in the recruitment of leukocytes to sites of inflammation. L-Selectin surface expression is rapidly down-regulated by inflammatory signals in vitro. In a prospective study, we found L-selectin expression on umbilical cord blood granulocytes and monocytes to be significantly decreased in newborn infants with acute bacterial infection compared with controls (p < 0.01). A significantly reduced L-selectin expression of both granulocytes and monocytes was also found to be associated with an increased neutrophil immature/total ratio (p < 0.01) but not with other laboratory markers of neonatal sepsis. There was no apparent impact of prematurity, low birth weight, gestational hypertension, or gestational diabetes on L-selectin expression. Although the mode of delivery did not affect granulocyte L-selectin expression, umbilical cord blood monocytes showed an increased L-selectin expression after emergency cesarean delivery compared with samples obtained after elective cesarean or vaginal delivery (p < 0.01). We conclude that acute systemic inflammation results in down-regulation of granulocyte and monocyte L-selectin expression in vivo similar to that observed in vitro.

Acute Disease↗

PubMed1994

Down-regulation of L-selectin surface expression by various leukocyte isolation procedures.

L-selectin, a cell surface glycoprotein expressed on lymphocytes, granulocytes, and monocytes, has been implicated in lymphocyte homing and extravasation of phagocytic leukocytes into areas of inflammation. Considerable differences of L-selectin expression among various individuals has been reported, with clinical correlations to perinatal events, maturation, and circadian rhythm. In this study, L-selectin expression of various white blood cells was found to be differentially sensitive to ficoll-hypaque or percoll density gradient centrifugation. After density gradient centrifugation, a significant loss of median monocyte L-selectin expression was observed when compared to time and temperature-matched controls or results obtained by whole blood incubation with anti-L-selectin monoclonal antibodies followed by simultaneous leukocyte fixation and red cell lysis. Mock treatment itself was associated with a variable L-selectin loss of monocytes but not lymphocytes or granulocytes. Ficoll-hypaque or percoll density gradient centrifugation resulted in significant L-selectin down-regulation of lymphocytes while granulocytes separated from lymphocytes and monocytes by ficoll-hypaque or percoll retained full L-selectin surface reactivity. L-selectin downregulation was seen also after colloid sedimentation with hydroxy-ethyl starch. It is concluded that unseparated blood should be used for measuring L-selectin expression.

Cell Adhesion↗

PubMed1994

Down-regulation of L-selectin surface expression by various leukocyte isolation procedures.

Cell Adhesion Molecules↗

PubMed1993

Superior prognosis in combined compared to isolated bone marrow relapses in salvage therapy of childhood acute lymphoblastic leukemia.

Three hundred twenty-six children with bone marrow (BM) relapse of non-B acute lymphoblastic leukemia (ALL) were stratified according to the time of relapse in three consecutive multicenter trials--ALL-REZ BFM 83, 85, and 87. Employing an intensive polychemotherapy regimen, extramedullary involvement appeared to be predictive of superior outcome in both strata as well as in the whole group (probability of 7-year event-free survival (EFS) 42% in combined vs. 15% in isolated BM relapse, P = 0.015). Children with combined BM relapse occurring later than 6 months after completion of front-line therapy reached EFS estimates of 60%. We conclude that results of conventional polychemotherapy with BFM relapse protocols are equivalent to those achieved by bone marrow transplantation in children with late combined BM relapse.

Adolescent↗

PubMed1993

Diminished cord blood lymphocyte L-selectin expression in neonatal bacterial infection.

L-Selectin, a leukocyte surface glycoprotein involved in white blood cell extravasation, is rapidly down-regulated after leukocyte activation. We prospectively determined lymphocyte L-selectin expression in freshly obtained cord blood samples of 98 neonates (gestational age 25-42 weeks). In eight infants with bacterial infection, the mean percentage of L-selectin(high) lymphocytes was 32.5% (SD 20.1%), compared to 60.1% (SD 18.7%) in the control group (P < 0.01). A percentage of L-selectin(high) lymphocytes of less than 42% had a sensitivity of 75% and a specificity of 82% in identifying infected newborns. Cord blood lymphocyte L-selectin expression was independent of gestational age, birth weight, umbilical artery pH, hematocrit, white blood cell count, absolute neutrophil count, C-reactive protein level, or maternal fever before delivery while there was a weak correlation with the newborn's immature/total ratio and platelet count. To our knowledge, this is the first report demonstrating downregulation of human lymphocyte L-selectin expression following activation of the immune system in vivo.

Cell Adhesion Molecules↗

PubMed1993

Cranial ultrasound findings in aspartoacylase deficiency (Canavan disease).

Canavan disease (CD) is a rare leukodystrophy which is lethal in infancy or early childhood. The underlying biochemical abnormality in CD is a hereditary deficiency of N-aspartoacylase transmitted in an autosomal recessive fashion. We report on the ultrasound (US), CT, and MRI findings of three unrelated boys with biochemically confirmed CD. At 6 and 9 months of age, two CD patients with rapid neurological deterioration showed markedly enhanced acoustic attenuation of the white matter with the exception of the corpus callosum, giving the appearance of a reversed pattern of echogenicity of cortical gray and subcortical white matter. While gyri and sulci had an almost normal US appearance, the periventricular gray matter featured prominently with increased echogenicity. In contrast another CD patient with a more protracted course had ventricular enlargement when examined by US at 5 and 9 months but no alteration in white matter echogenicity. MRI showed impaired myelinization in all three patients with Canavan disease.

Canavan Disease↗

PubMed1992

Lymphocyte activation and regulation of three adhesion molecules with supposed function in homing: LECAM-1 (MEL-14 antigen), LPAM-1/2 (alpha 4-integrin) and CD44 (Pgp-1).

Directed migration of lymphocytes from blood into lymph nodes and gut-associated lymphatic tissue, also referred to as homing, is subject to change following activation. Lymphocyte migration into lymphoid organs in vivo and binding to high endothelial venules in vitro is largely suppressed after short-term stimulation with phorbol esters. The observed functional alterations were correlated with changes in the expression of three putative homing receptors, LECAM-1 (MEL-14 antigen), LPAM-1/2 (alpha 4-integrin) and the murine CD44 (Pgp-1, H-CAM, Hermes-antigen equivalent) upon different modes of cellular activation. Expression of LECAM-1 (gp90 MEL-14), a lymphocyte adhesion molecule implicated in targeting extravasation into lymph nodes, was found to be lost almost completely within minutes after protein kinase C activation. LECAM-1 re-expression occurred within less than 24 h. Rapid loss of LECAM-1 was also observed after calcium ionophores whereas anti-CD3 or concanavalin A elicited a gradual and heterogeneous loss of LECAM-1 becoming detectable after several hours only. A number of cytokines tested were not able to induce alterations in LECAM-1 expression. In contrast, expression of LPAM-1/2 (alpha 4-integrin) and CD44 (Pgp-1, H-CAM), two adhesion molecules supposed to direct extravasation into Peyer's patches, remained stable for hours after every stimulus tested; CD44 expression gradually increased 24 h after mitogenic activation, whereas a small reduction only was observed for the expression of the alpha 4-chain under certain conditions. Thus, reduced extravasation of lymphocytes into Peyer's patches after activation is not due to a decline in the surface density of LPAM-1/2 alpha-chain or CD44 whereas alterations in migration into lymph nodes parallel the expression of LECAM-1.

Animals↗

PubMed1992

Locomotion of human bone marrow and peripheral blood leukocytes is associated with maturational stage and altered in malignancy.

Using high-resolution phase contrast time-lapse microcinematography, slow movements (0.8-2.0 microns/minute) of human myeloblasts, monoblasts, and megakaryocytes can be recorded. Upon maturation to promyelocytes, motility is lost until cells have reached the stage of metamyelocytes (0.4 microns/minute). Motility increases sharply following maturation into segmented neutrophils (20.4 microns/minute). Monocytes and promonocytes display a mean track velocity of 7.1 microns/minute. The distribution of lymphocyte velocities is not bell-shaped but shows three maxima of 2.1 microns/minute, 7.8 microns/minute, and 18.4 microns/minute. Atypical lymphocytes from patients with infectious mononucleosis belong to the fast group, whereas lymphocytes activated in vitro by mitogens belong to the slow group. Red blood cell precursors from normal human bone marrow do not move actively. In contrast, erythroleukemic blasts show a motility comparable to normal myeloblasts. Similarly, acute promyelocytic leukemia cells move at 6.7 microns/minute, while their normal counterparts are sessile. Increased motility is also observed in blast cells from a variety of acute myelogenous and lymphoblastic leukemias.

Bone Marrow Cells↗

PubMed1991

Blood mononuclear cells from patients with severe congenital neutropenia are capable of producing granulocyte colony-stimulating factor.

Severe congenital neutropenia (SCN) is a disorder of myelopoiesis characterized by severe neutropenia or absence of blood neutrophils secondary to a maturational arrest at the level of promyelocytes. We examined peripheral blood mononuclear cells (PBMC) of SCN patients who demonstrated normalization of their blood neutrophil counts in a phase II clinical study with recombinant human granulocyte colony-stimulating factor (rhG-CSF). When stimulated in vitro with bacterial lipopolysaccharides (LPS), PBMC of those SCN patients produced G-CSF activity, as judged by proliferation induction of the murine leukemia cell line, NFS-60. Western and Northern blot analysis showed G-CSF protein and G-CSF-mRNA indistinguishable in size from those of normal controls. We conclude that PBMC of the SCN patients tested are capable of synthesizing and secreting biologically active G-CSF in vitro.

Adult↗

PubMed1991

SD-mice--an animal model for complex anorectal malformations.

Animal models for morphological investigations of anorectal malformations are barely known to pediatric surgeons. In this study the morphological characteristics of a spontaneous mutation of the house mouse, the so-called SD-mouse, are described. The semidominant gene SD exerts its influence on the anorectum, the urogenital system and the axial skeleton. Many heterozygous (SD/+) and all homozygous (SD/SD) animals die shortly after birth due to their malformations. Surviving heterozygotes, identified by their short and deformed tails, may be used for breeding purposes. According to Mendel's laws, mating of such heterozygous yields 75% more or less malformed animals which may be used for morphological investigations. The morphological features of these animals were investigated in 61 neonatal SD-mice (33 SD/SD, 28 SD/+) and in 10 normal controls by microdissection and in 49 animals (25 SD/SD, 20 SD/+ and four normal controls) by serial sections. Of these, all homozygous and 10 heterozygous SD mice had anorectal malformations. The spectrum of these malformations is wide: very complex malformations in SD/SD mice and high anorectal malformations in SD/+ mice. These are comparable to morphological features found in humans and piglets. Hence the SD mouse represents an animal model for morphologic and embryonic investigations of complex anorectal malformations.

Anal Canal↗

PubMed1991

Erythroblastopenia in two patients after splenectomy and polychemotherapy.

Acquired erythroblastopenia is a rare disorder of the hematopoietic system associated with viral infections, autoimmune diseases, and drugs. We report on two patients who became anemic due to maturation-arrest at the proerythroblast level, without alterations of white blood cell or platelet counts. Both patients had been splenectomized and had undergone chemotherapy for nephroblastoma or Hodgkin's disease, respectively, at the same pediatric oncology unit. Erythropoietin levels were elevated in both patients. Antibodies against specific viruses, particularly parvovirus B 19, could not be detected in patient sera. Both patients responded to infusions of 7 S immunoglobulin with a rapid increase of the reticulocyte counts. In both cases, complete clinical remission was observed after a duration of 5 months. Heat-inactivated serum obtained during the acute phase and after remission as well was found to be inhibitory for normal bone marrow granulocyte and erythrocyte progenitor growth in vitro. The simultaneous appearance of this rare disorder in two otherwise unrelated patients treated at the same unit prompts speculations about a viral etiology.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1990

Establishment and characterization of a granulocyte-macrophage colony-stimulating factor-dependent human myeloid cell line.

A new human myeloid cell line has been established recently from the bone marrow cells of a patient with chronic myelogenous leukemia in blast crisis. The active proliferation and survival of the cells in RPMI 1640 medium containing fetal calf serum are clearly dependent on the presence of either natural or recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF). Despite permanent culturing in rhGM-CSF (100 U/mL), the cells do not differentiate and bear the myelomonocytic surface markers CD34, CD13, CD36, as well as HLA-DR, but not CD3, CD7, CD10, CD11b, CD14, CD20, or CD42b. The predominant karyotype, apart from tetraploidy in several cells, is 45, XX, -9, -17, -19, -22, 7p-, 9q+ (der t[9;22]), der (13q), with three additional marker chromosomes, from which one was observed in the patient's leukemic cells. On BglII-digested DNA, Southern blot analysis with bcr 5' as the probe detected two additional hybridizing restriction fragments of 8.6 and 11.0 kilobase pairs.

Blast Crisis↗