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Biomedical subjects

K Lechner

Publications and source records attributed to K Lechner.

At least 109 records · Page 6Linked to original sources

Clonality analysis using X-chromosome inactivation at the human androgen receptor gene (Humara). Evaluation of large cohorts of patients with chronic myeloproliferative diseases, secondary neutrophilia, and reactive thrombocytosis.

Chronic myeloproliferative diseases (MPDs) are not associated with consistent cytogenetic or molecular abnormalities. Demonstration of clonal cell growth by analysis of X-chromosome inactivation (XCI) patterns in females provides a promising tool for diagnosis. However, this technique can be complicated by excessive lyonization of normal cells mimicking clonal cell growth: We analyzed XCI patterns at the human androgen receptor (HUMARA) locus in 146 healthy females, 65 women with secondary neutrophilia, 31 women with reactive thrombocytosis, and 86 women with chronic MPDs. A skewed XCI pattern with greater than 75% amplification of 1 allele (allele ratio > 3:1) was found in 22 (9.1%) of 242 control subjects. The incidence of skewing was statistically significantly lower in women younger than 30 years (2/73) compared with women older than 60 years (10/53). Of 86 patients with a chronic MPD, 71 (82%) exhibited an allele ratio greater than 3:1, whereas only 10 (12%) of 86 age-matched control subjects showed a skewed XCI pattern. Although statistical evaluation of the data showed a significant difference between patients with a chronic MPD and control subjects, proof of clonality in individual, especially elderly, patients is difficult.

Adolescent↗

No evidence for an increased risk of venous thrombosis in patients with factor V Leiden by the homozygous 677 C to T mutation in the methylenetetrahydrofolate-reductase gene.

Hyperhomocysteinemia is an established risk factor for arterial and venous thrombosis. Recently, it has been shown that a C to T mutation at nt position 677 in the methylenetetrahydrofolate-reductase (MTHFR) gene is a common cause of moderately elevated levels of plasma homocysteine in adults. In order to investigate whether the newly recognized genetic alteration in the MTHFR gene potentiates the thrombotic tendency in patients with factor V Leiden, we studied 81 unrelated patients with a history of venous thrombosis and a heterozygous factor V Leiden mutation. In addition, we analyzed 111 family members of 34 families in which the proband had a heterozygous factor V Leiden mutation. In all individuals, factor V Leiden and the MTHFR mutation were tested and the occurrence of venous thrombotic events was evaluated retrospectively. Seventy-seven healthy subjects without the factor V Leiden mutation or any other known thrombotic risk factor served as a control group. The prevalence of the homozygous MTHFR mutation was similar in index patients (10 of 81, 12%) and in the control group (10 of 77, 13%). The median age at first thrombosis in index patients was 32 years (range 22-69 years) in 10 patients with heterozygous factor V Leiden and T/T MTHFR mutation, and 34 years (range 6-72 years) in 71 patients with the factor V Leiden mutation only. In the family members, the prevalence of thrombosis was not higher in patients with factor V Leiden and +/+ MTHFR genotype than in those with only the heterozygous factor V Leiden mutation. We conclude from these data that the 677 C to T mutation in the MTHFR gene does not represent a significant additional risk factor for venous thrombosis in patients with factor V Leiden mutation.

Adolescent↗

The effect of interferon alpha on myeloproliferation and vascular complications in polycythemia vera.

The effect of interferon alpha (IFN) on myeloproliferation and vascular complications was studied in 32 patients (17 female, 15 male; median age 60.5 yr) with polycythemia vera (PV). IFN therapy was initiated at a median time of 19 months after diagnosis. Ten patients were pretreated with chemotherapy in addition to phlebotomy. IFN dose was 12 megaU/wk during the first year, 9 megaU/wk during the second year and 12 megaU/wk thereafter. During IFN alpha treatment hematocrit level was 45.7% and remained at this level after the second year of treatment, compared to 46.5% before IFN. The frequency of phlebotomy before IFN was 0.49/month and dropped to 0.19/month (p <0.0005) during the first year of IFN treatment. IFN normalized high platelet and leukocyte counts in a majority of patients. The incidence of deep venous thromboses was 3.6%/yr before IFN alpha and 1.8%/yr during the first year of treatment. IFN-induced side-effects were mainly flu-like symptoms, fever, fatigue and arthralgia. In conclusion, IFN allowed the reduction of the dose of chemotherapy and decreased the need of phlebotomy. Despite improvement of hematological parameters, it is still uncertain whether IFN alpha can improve clinical symptoms in PV.

Adult↗

Large amounts of vascular endothelial growth factor at the site of hemostatic plug formation in vivo.

Vascular endothelial growth factor (VEGF) is important for the proliferation, differentiation, and survival of microvascular endothelial cells. It is a potent angiogenic factor and a specific endothelial cell mitogen that increases fenestration and extravasation of plasma macromolecules. Recently, large quantities of VEGF were detected in human megakaryocytes. Incubation of human platelets with thrombin in vitro resulted in the release of large amounts of VEGF. To investigate whether VEGF is released from platelets during coagulation activation in vivo, we measured in human subjects VEGF at the site of plug formation, ie, in blood emerging from a standardized injury made to determine bleeding time (shed blood). VEGF was also determined in the same volunteers after treatment with the specific thrombin inhibitor recombinant hirudin (r-hirudin). In a double-blind, randomized, crossover study, 17 healthy male volunteers (aged 20 to 35 years) were investigated. VEGF concentrations were measured in venous blood and in shed blood by the use of an immunoassay 10 minutes after intravenous administration of r-hirudin (0.35 mg/kg of body weight) or physiological saline. Prothrombin fragment f1.2 (f1.2) and beta-thromboglobulin (beta-TG) were determined as indicators of coagulation and platelet activation, respectively. Concentrations of VEGF, f1.2, and beta-TG in shed blood 4 minutes after injury were significantly higher than in venous blood (VEGF, 55.8+/-9.2 versus <20 pg/mL, P<0.001; f1.2, 71.3+/-10.4 versus 0.78+/-0.03 nmol/L, P<0. 001; beta-TG, 2290+/-170 versus 53.2+/-14.0 ng/mL, P<0.001). Administration of r-hirudin caused a >50% inhibition of the beta-TG and f1.2 levels in shed blood. In a similar manner, much lower amounts of VEGF were detectable at the site of plug formation after r-hirudin treatment (69.0+/-9.5 versus 37.8+/-2.6 pg/mL per minute; P=0.0015). Our data indicate that substantial quantities of VEGF are released from platelets during the interaction with the injured vessel wall in vivo. This finding may be relevant with respect to wound healing and tissue repair, tumor vascularization, or arterial thrombus formation.

Adult↗

Persisting bone marrow aplasia following interferon-alpha combined with ara-C for chronic myelogenous leukemia.

A 37-year-old man with a newly diagnosed chronic myelogenous leukemia received induction therapy with hydroxyurea and interferon-alpha, and maintenance therapy with low-dose ara-C and interferon-alpha. Subsequent to a rapid hematological remission, a continuously aggravating pancytopenia with bone marrow aplasia developed which persisted after withdrawal of maintenance therapy. Bone marrow examination exhibited aplastic areas and residual hematopoiesis with impaired maturation; cytogenetically, there was a 100% persistence of Philadelphia chromosome-positive metaphases. By allogeneic bone marrow transplantation, a complete reconstitution of hematopoiesis was achieved.

Adult↗

Homocysteine levels in polycythaemia vera and essential thrombocythaemia.

Patients with polycythaemia vera (PV) or essential thrombocythaemia (ET) have an increased risk of arterial and venous thromboembolic complications. Since hyperhomocysteinaemia (HHC) is a risk factor for vascular disease, we investigated the frequency of HHC in these disorders and analysed a possible association of elevated plasma homocysteine levels with vascular complications. In the cohort of 134 patients from Vienna (69 female, 65 male, median age 65.5 years, range 21-91 years) with PV (n = 74) or ET (n = 60), plasma homocysteine levels were significantly higher compared to 134 healthy controls. Median homocysteine level was 12.3 micromol/l (range 3.5-48.4 micromol/l) in patients with PV or ET and 8.9 micromol/l (range 4.8-30.5 micromol/l) in normal controls (P < 0. 0001). In addition to the 134 patients from Vienna, 48 patients (28 female, 20 male; median age 66.5 years, range 24-82) from Vicenza with PV (n = 25) or ET (n = 23) were included to evaluate the impact of HHC on the risk of thrombosis. Of 59 patients with HHC (44 from Vienna and 15 from Vicenza) 18 (31%) had a history of arterial and 10 (17%) of venous thrombosis. Of 123 patients with normal homocysteine levels, 30 (24%) had arterial and 16 (13%) had venous thromboses. The difference between the two groups was statistically not significant. Even though mild to moderate HHC occurred in a larger number of patients with PV or ET and thrombosis, it can presently not be regarded as an additional risk factor for thrombosis.

Adult↗

The risk of early recurrent venous thromboembolism after oral anticoagulant therapy in patients with the G20210A transition in the prothrombin gene.

A G20210A transition in the prothrombin gene is a common risk factor of venous thrombosis. The risk of recurrent venous thromboembolism in carriers of the 20210A allele is unknown and guidelines for secondary thromboprophylaxis in these patients are not available. In a prospective multicenter trial, 492 patients with a history of objectively documented venous thromboembolism were followed for a mean observation time of 24+/-16 months after discontinuation of oral anticoagulants. Forty-two patients (8.5%) were carriers of the 20210A allele. Three of the 42 patients with the G20210A mutation (7%) and 54 of 450 patients without the mutation (12%) experienced recurrent venous thrombosis. At 24 months, the probability of recurrence was 8% (95% CI 0-16.7) in patients with the mutation and was 12.2% (95% CI 8.8-15.6) in patients without the mutation. In conclusion, the risk of early recurrent venous thromboembolism is not higher in patients with the G20210A mutation than in those without the mutation. Therefore, long-term secondary thromboprophylaxis with oral anticoagulants in heterozygous carriers of the 20210A allele is not justified.

Administration, Oral↗

Solid tumors and factor VIII antibodies.

PURPOSE: To analyze the association between solid tumors and the occurrence of factor VIII antibodies and the response to treatment. PATIENTS AND METHODS: Published case reports describing the association of a solid tumor and a factor VIII antibody retrieved from 20 data bases. 40 cases were reported and 27 cases were analyzable. RESULTS: Factor VIII antibodies occurred in a close temporal relationship with the detection of the tumor in most cases. No association with a specific type of tumor could be identified. Immune suppressive treatment with prednisone +/- cyclophosphamide was successful in the majority of cases. CONCLUSION: It is likely that there is a causal association between some solid tumors and factor VIII antibodies, but it is an extremely rare complication of cancer. The immunoglobuline nature of the inhibitor and the good response to immune suppressive treatment suggests that it is an autoimmune phenomenon. The pathogenesis is unknown.

Aged↗

Prospective evaluation of hemostatic system activation and thrombin potential in healthy pregnant women with and without factor V Leiden.

Normal pregnancy is associated with alterations of the hemostatic system towards a hypercoagulable state and an increased risk of venous thromboembolism. The risk of venous thrombosis is higher in pregnant women with factor V Leiden (FVL) than in those with wildtype factor V. Routine laboratory assays are not useful to detect hypercoagulable conditions. A prospective and systematic evaluation of hemostatic system activation in women with and without FVL during an uncomplicated pregnancy employing more sensitive markers of hypercoagulability, such as prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT), D-Dimer, or the endogenous thrombin potential (ETP), an indicator of the plasma's potential to generate thrombin, has not been performed. We prospectively followed 113 pregnant women with (n = 11) and without (n = 102) FVL and measured F1+2. TAT, D-Dimer and the ETP at the 12th, 22nd and 34th gestational week as well as 3 months after delivery (baseline) in each subject. None of the women developed clinical signs of venous thromboembolism during pregnancy or postpartum. Pregnant women with and without FVL exhibited substantial activation of the coagulation and fibrinolytic system as indicated by a gradual increase of F1+2, TAT and D-Dimer throughout uncomplicated pregnancy up to levels similar to those found in acute thromboembolic events (p < 0.0001 by analysis of variance for each parameters). Levels of F1+2 and TAT were comparable between women with and without FVL, but levels of D-Dimer were significantly higher in women with FVL than in those without the mutation (p = 0.0005). The ETP remained unchanged in both women with and without FVL at all timepoints. Our data demonstrate a substantial coagulation and fibrinolytic system activation in healthy women with and without FVL during uncomplicated pregnancy. An elevated F1+2, TAT or D-Dimer level during pregnancy is not necessarily indicative for an acute thromboembolic event. The normal ETP in both women with and without FVL suggests that the capacity of the plasma to generate thrombin after in vitro activation of the clotting system is not affected by pregnancy. Higher levels of D-Dimer in women with FVL than in women with wildtype factor V at baseline as well as during pregnancy indicate increased fibrinolytic system activation in carriers of the mutation.

Adult↗

Treatment of acute leukemia.

Leukemic cells are highly sensitive to chemotherapeutic agents. A reduction of the leukemic burden is easily achieved by chemotherapy in most cases. However, it is difficult to reduce the number of leukemic cells to such an extent that a regrowth does not occur and the patient is cured. Traditionally the therapy of acute leukemia is divided into induction and post remission therapy. The aim of the induction therapy is to reduce the number of leukemic cells to a morphologically undetectable level allowing normal hemopoiesis to recover. The goal of the post remission treatment is a further reduction of leukemic cells to zero or to very low levels which can be controlled by (still unknown) endogenous mechanisms. In some recent treatment protocols induction and the early part of post remission treatment are not strictly separated.

Acute Disease↗

[Advances in the treatment of chronic lymphocytic leukemia (CLL)].

CLL is a chronic lymphoproliferative disorder which is characterized by the proliferation of a CD5 positive B cell clone. At diagnosis most patients are in early stage of the disease (stage A). It is well established that an early treatment in stage A is not associated with a survival advantage. Therefore, the disease should be treated only when signs of progression are present. The standard initial therapy is chlorambucil +/- prednisone. By this treatment remissions (mostly partial remissions) are achieved in about half of the patients. Fludarabine, a purine analogue, is more effective than chlorambucil as initial treatment (75% remissions, 27% complete remissions, 33 months progression free survival). However, the overall survival is not prolonged when compared to chlorambucil treatment. Fludarabine has a high efficacy in patients with recurrent disease, in particular in those who are resistant to alkylating agents. The allogeneic and autologous stem cell transplantation is an experimental treatment which may be indicated in younger patients who show a response to conventional treatment. With both procedures hematological remissions are frequently achieved and in some of the patients long lasting molecular remissions were obtained. Currently, it is unknown whether patients can be cured by stem cell transplantation and longer follow-up will be necessary to clarify this question. Monoclonal B-cell antibodies are effective in vivo and partial remissions can be obtained in chemotherapy refractory patients. Antibodies have a high efficacy in clearing lymphoma cells from peripheral blood and bone marrow but are less effective on the organomegaly.

Antineoplastic Combined Chemotherapy Protocols↗

Interleukin-10 inhibits erythropoietin-independent growth of erythroid bursts in patients with polycythemia vera.

In polycythemia vera (PV) erythroid colonies that grow in vitro in the absence of exogenous erythropoietin (EPO) arise from the abnormal clone that is responsible for overproduction of red blood cells. Although the mechanism of autonomous formation of burst-forming units-erythroid (BFU-E) is not fully understood, a spontaneous release of growth regulatory molecules by PV cells and/or by accessory cells is likely to be involved. Because of its cytokine synthesis inhibiting action, interleukin-10 (IL-10) could be a potentially useful molecule to modulate abnormal erythropoiesis in PV. We studied the effect of recombinant human IL-10 on the EPO-independent growth of erythroid bursts derived from peripheral blood mononuclear cells (PBMNCs) of patients with PV. IL-10 showed a profound, dose-dependent, and specific inhibitory effect on autonomous BFU-E formation. Ten nanograms per milliliter of IL-10 significantly suppressed spontaneous growth of erythroid colonies in methylcellulose in five of five PV patients tested with a mean inhibition by 81% (range, 72-94). To elucidate the possible mechanism of the inhibitory action of IL-10 we further studied the effect of anticytokine antibodies on autonomous BFU-E growth and the ability of exogenous cytokines to restore IL-10-induced suppression of erythroid colony growth. Among a panel of growth regulatory factors tested (granulocyte-macrophage colony-stimulating factor [GM-CSF], IL-3, granulocyte colony-stimulating factor, stem cell factor, and insulin-like growth factor-1) GM-CSF was the only molecule for which both an inhibition of spontaneous BFU-E formation by its respective antibody as well as a significant restimulation of erythroid colonies in IL-10-treated cultures by exogenous addition was found. Moreover, inhibition of GM-CSF production by IL-10 was shown in PV PBMNCs at the mRNA level. Our data indicate that autonomous BFU-E growth in PV can be profoundly inhibited by IL-10 and that this inhibitory effect seems to be at least in part secondary to suppression of endogenous GM-CSF production.

Adult↗

Subdural hygromas after bone marrow transplantation: results of a prospective study.

BACKGROUND: Subdural hygromas after bone marrow transplantation (BMT) have been occasionally found in patients with persisting headache and vomiting. We assessed the incidence of subdural hygromas after BMT and tried to define possible risk factors associated with this complication. METHODS: Fifty bone marrow graft recipients surviving more than 30 days were consecutively enrolled into a prospective study. Cranial CT scans were performed before and 30 days after BMT. Clinical data and symptoms were recorded daily during the first 30 days after BMT. In patients with subdural hygromas, a magnetic resonance imaging scan and monthly follow-up cranial computed tomography scans were performed until fluid collections had resolved completely. RESULTS: In 9 of the 50 patients (18%) who survived 30 days after transplantation, newly acquired subdural hygromas were found. Patients with hygromas suffered significantly longer and more severely from headache and vomiting (P=0.01). Application of intrathecal methotrexate and arterial hypertension occurred significantly more often in patients with hygromas (P=0.01). In a stepwise logistic regression model, arterial hypertension and intrathecal methotrexate application were the only independent risk factors for the development of hygromas. Monthly follow-up cranial computed tomography scans showed that all hygromas resolved completely after a median of 60 days after diagnosis (range: 30-120 days). CONCLUSIONS: Subdural hygromas are a frequent complication after BMT within the first 30 days after transplantation. They are reversible and disappear within 2-3 months. The need for routine application of intrathecal methotrexate in standard risk leukemia patients should be critically addressed. Furthermore, close monitoring of blood pressure and immediate antihypertensive therapy might contribute to avoid formation of subdural hygromas.

Adolescent↗

Expression of the lung resistance protein predicts poor outcome in de novo acute myeloid leukemia.

The 110-kD lung resistance protein (LRP) is overexpressed in P-glycoprotein-negative multidrug-resistant cell lines and most likely involved in the multidrug resistance (MDR) of these cell lines. To determine the clinical significance of LRP, we have studied LRP expression of leukemic blasts and its association with clinical outcome in patients with de novo acute myeloid leukemia (AML). LRP expression of leukemic blasts obtained from peripheral blood or bone marrow of previously untreated patients (n = 86) was determined by immunocytochemistry by means of monoclonal antibody LRP-56. LRP expression at diagnosis was detected in 31 (36%) patients. LRP expression was independent of age and sex of the patients, French-American-British subtype, cytogenetic abnormalities, and lactate dehydrogenase levels, but correlated with white blood cell count (P = .01). Eighty-two patients received standard induction chemotherapy that included cytarabine and MDR drugs (daunorubicin in most patients, additional etoposide in the majority of patients). The complete remission rate of induction chemotherapy was 72% (95% confidence interval [CI] = 61% to 82%) for the total study population. The complete remission rate was 81% (95% CI = 67% to 91%) for patients without LRP expression but only 55% (95% CI = 36% to 74%) for patients with LRP expression (P = .01). Overall survival and disease-free survival were estimated according to Kaplan-Meier in 82 and 59 patients, respectively. Overall survival was significantly longer in patients without LRP expression than in patients with LRP expression. At a median follow-up of 16 months, median overall survival was 17 months (95% CI = 12 to 38 months) for LRP-negative patients but only 8 months (95% CI = 4 to 12 months) for -positive patients (P = .006). Disease-free survival was 9 months (95% CI = 7 to 11 months) for LRP-negative patients and 6 months (95% CI = 5 to 8 months) for -positive patients (P = .078). Outcome was best in patients lacking both LRP and P-glycoprotein expression. In conclusion, LRP predicts for poor outcome and thus the LRP gene appears to be another clinically relevant drug resistance gene in AML.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Detection of mi transcription factor (MITF) mRNA in a case of myelodysplastic syndrome and bone marrow mastocytosis.

Myelodysplastic syndromes (MDS) may be accompanied by systemic mastocytosis. The mechanisms which play a role in the evolution of mastocytosis, however, are not well understood. We report on a case of refractory and anemia with ringed sideroblasts (RARS), and co-existing bone marrow mastocytosis. Compact mast cell (MC) infiltrates were detected in bone marrow sections by immunohistochemistry using an antibody to tryptase. In addition, the MC were found to express c-kit, the tyrosine kinase receptor for MGF (mast cell growth factor = stem cell factor, SCF). Activating point mutations in the kinase domain of c-kit (often found in mastocytosis) were not detectable. However, the mononuclear cells (MNC) of the bone marrow expressed mRNA specific for MITF, a transcription factor that regulates expression of c-kit and differentiation of MC. Surprisingly, the c-kit ligand SCF was found to augment expression of MITF mRNA in bone marrow MNC. Whether this augmentation represents a general response (preventing loss of growth factor receptor expression during cell maturation) common to all types of hemopoietic progenitors, or is confined to (some forms of) mastocytosis, remains unknown.

Aged↗

Low-molecular-weight heparin-induced skin necrosis.

We report a case of low-molecular-weight heparin (LMWH)-induced skin necrosis in a patient with chronic lymphatic leukemia. The patient had heparin-PF4 antibodies and the heparin-induced platelet activation (HIPA) test was positive, but platelet counts remained normal. Analysis of seven cases of LMWH-induced skin necrosis revealed that this complication occurred mostly in patients previously exposed to heparin, and that severe problems such as thrombocytopenia or thromboembolic complications were rare. This is in contrast to skin necrosis induced by unfractionated heparin (UFH), where a substantially higher number of patients suffered from thrombocytopenia and thromboembolism. In addition, most patients with UFH-induced skin necrosis were not pretreated with heparin. Therefore, it is possible that LMWH is less immunogenic than UFH and requires repeated exposure for induction of skin necrosis.

Fibrinolytic Agents↗

Graft-versus-host disease following second syngeneic stem cell transplantation for relapsed chronic myeloid leukemia.

Allogeneic bone marrow transplantation is the only curative treatment for patients with Philadelphia chromosome-positive chronic myeloid leukemia (CML); however, recurrence of disease remains a major cause of treatment failure. A 26-year-old man with chronic myeloid leukemia who had a cytogenetic relapse 49 months after his first syngeneic bone marrow transplant (BMT) and hematologic relapse 23 months thereafter progressed to blast crisis despite treatment with IFN-alpha for 15 months. He underwent a second transplantation in early second blast crisis, 92 months after the first BMT with PBPC from his previous donor. Successful hematological reconstitution occurred. On day 50 after the second transplantation the patient developed a generalized rash, hepatomegaly, and cholestatic signs. Skin and liver biopsy revealed changes compatible with acute graft-versus-host disease (GVHD). Treatment with cyclosporin A (CSA) and prednisone was started, and the GVHD resolved. Fifteen months after PBPC transplantation he had a molecular relapse. Despite discontinuation of CSA, the patient progressed into blast crisis 7 months later. The occurrence of GVHD and disappearance of the BCR-ABL-positive clone suggest that a graft-versus-leukemia (GVL) effect may have been operative for 15 months in a patient given a second syngeneic BMT in blast crisis.

Adult↗

Acquired factor V inhibitors.

One hundred and five cases of factor V inhibitors were published between 1955 and 1997. According to pathogenesis, factor V inhibitor patients can be divided into five groups: patients exposed to bovine thrombin; patients after surgery without exposure to bovine proteins; miscellaneous associated conditions; 'idiopathic' inhibitors; inhibitors in congenital factor V deficiency. The clinical and biochemical properties are described. The overall prognosis of factor V inhibitors is good, but there are differences among the five groups with the best prognosis in patients exposed to bovine thrombin and the worst prognosis in 'idiopathic' inhibitors. Only a few treatment options are available. Immunoadsorption and plasmapheresis seem to be the most effective methods for therapy of acute bleeding. Many inhibitors disappear spontaneously and it is uncertain whether an immunosuppressive treatment hastens the disappearance of the inhibitor.

Animals↗