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Biomedical subjects

M Freund

Publications and source records attributed to M Freund.

At least 19 recordsLinked to original sources
PubMed2000

ADP induces partial platelet aggregation without shape change and potentiates collagen-induced aggregation in the absence of Galphaq.

Platelets from Galphaq knockout mice are unable to aggregate in response to physiological agonists like adenosine 5'-diphosphate (ADP), thromboxane A(2), thrombin, or collagen, although shape change still occurs in response to all of these agonists except ADP. ADP-induced platelet aggregation results from simultaneous activation of the purinergic P2Y(1) receptor coupled to calcium mobilization and shape change and of a distinct P2 receptor, P2cyc, coupled through Gi to adenylyl cyclase inhibition, which is responsible for completion and amplification of the response. P2cyc could be the molecular target of the antithrombotic drug clopidogrel and the adenosine triphosphate (ATP) analogs AR-C69931MX, AR-C67085, and AR-C66096. The aim of the present study was to determine whether externally added ADP could still act through the Gi pathway in Galphaq-deficient mouse platelets and thereby amplify the residual responses to agonists such as thrombin or collagen. It was found that (1) ADP and adrenaline still inhibited cyclic AMP accumulation in Galphaq-deficient platelets; (2) both agonists restored collagen- but not thrombin-induced aggregation in these platelets; (3) the effects of ADP were selectively inhibited in vitro by the ATP analog AR-C69931MX and ex vivo by clopidogrel and hence were apparently mediated by the P2cyc receptor; and (4) high concentrations of ADP (100 micromol/L) induced aggregation without shape change in Galphaq-deficient platelets through activation of P2cyc. Since adrenaline was not able to induce platelet aggregation even at high concentrations, we conclude that the effects of ADP mediated by P2cyc are not restricted to the inhibition of adenylyl cyclase through Gi(2).

Adenosine Diphosphate↗
PubMed2000

Myelodysplastic syndrome and acute myelogenous leukemia secondary to heart transplantation.

Myelodysplastic syndrome and acute myelogenous leukemia secondary to radiotherapy, radiation exposure, and chemotherapy is a well-documented malignant stem cell disorder. The incidence and natural course of myelodysplastic syndrome and acute myelogenous leukemia after organ transplantation remains less thoroughly investigated. In our institution, 631 heart transplantations have been performed between 1983 and 1998. We report five patients (age, 22-63 years) with myelodysplastic syndrome (MDS) (n=1) or acute myelogenous leukemia (AML) (n=4) occuring 4-8 years after transplantation. Immunosuppression consisted uniformly of a combination of prednisone, cyclosporine, and azathioprine. Successful cytogenetic analysis was performed in three patients, showing typical cytogenetic abnormalities in each case. The course of AML was uniformly fatal. One patient with MDS, refractory anemia with excess of blasts according to the FAB criteria, is alive with transfusion dependency 32 months after diagnosis. MDS and AML may occur during immunosuppression after heart transplantation. Treatment results are poor in this subgroup of patients with secondary leukemia.

Adult↗
PubMed2000

Classical Ehlers-Danlos syndrome caused by a mutation in type I collagen.

Classical Ehlers-Danlos syndrome (EDS) is characterized by skin hyperelasticity, joint hypermobility, increased tendency to bruise, and abnormal scarring. Mutations in type V collagen, a regulator of type I collagen fibrillogenesis, have been shown to underlie this type of EDS. However, to date, mutations have been found in only a limited number of patients, which suggests genetic heterogeneity. In this article, we report two unrelated patients with typical features of classical EDS, including excessive skin fragility, in whom we found an identical arginine-->cysteine substitution in type I collagen, localized at position 134 of the alpha1(I) collagen chain. The arginine residue is highly conserved and localized in the X position of the Gly-X-Y triplet. As a consequence, intermolecular disulfide bridges are formed, resulting in type I collagen aggregates, which are retained in the cells. Whereas substitutions of glycine residues in type I collagen invariably result in osteogenesis imperfecta, substitutions of nonglycine residues in type I collagen have not yet been associated with a human disease. In contrast, arginine-->cysteine substitutions in type II collagen have been identified in a variety of chondrodysplasias. Our findings show that mutations in other fibrillar collagens can be causally involved in classical EDS and point to genetic heterogeneity of this disorder.

Amino Acid Motifs↗
PubMed2000

Magnetisation transfer ratio is low in normal-appearing cerebral white matter in patients with normal pressure hydrocephalus.

We measured the magnetisation transfer ratios (MTR) of normal-appearing rostral (PR) and caudal (PC) periventricular white matter, the genu (CG) and the splenium (CS) of the corpus callosum and the thalamus (TH) in 12 patients with normal-pressure hydrocephalus (NPH) and compared them with 16 healthy control subjects. We found a significantly lower MTR in the NPH group than in the normal group for PR, PC, CG, and CS but not for TH. MT measurements give additional information which cannot be gained by conventional MRI, suggesting that NPH is associated with diffuse white matter damage, even in normal-appearing cerebral white matter.

Adult↗
PubMed2000

Oxidative burst measurement in patients treated with cytostatics: influence of G-CSF and role as a prognostic factor.

The ability to generate reactive oxygen species, the so-called oxidative burst, is essential for neutrophils to kill infectious micro-organisms. Flow cytometry was used to study oxidative burst prior to, during, and after cytostatic therapy. Seven patients were treated according to the DexaBEAM regimen with 12 cycles monitored. Four patients were treated according to the B-NHL regimen in which nine cycles were monitored. Ten healthy volunteers were chosen as a control group without any treatment. Neutrophils were collected from heparinized peripheral blood and were stimulated by phorbol-12-myristate-13-acetate (PMA), N-formyl-methionyl-leucyl-phenylalanine (FMLP), and Escherichia coli. The oxidative burst was estimated by the amount of nonfluorescent dihydrorhodamine 123 converted to green fluorescent rhodamine 123. Measurements were done daily. The FMLP-induced burst was enhanced in patients before therapy as compared with the control group, whereas PMA-induced burst was decreased slightly. E. coli-, FMLP-, and PMA-induced oxidative burst decreased in both groups during cytostatic therapy. E. coli-induced burst increased again within 2 days of G-CSF treatment in vivo. FMLP-induced burst increased in the B-NHL group but decreased in the DexaBEAM group. In patients who have recovered from leukopenia the oxidative burst is still partly suppressed. PMA-induced oxidative burst measured at the start of therapy correlates with infectious complications. Thus, PMA-induced burst may be used as a simple method for evaluating the individual risk of infections during therapy. The results demonstrate the modulating effect of cytostatic drugs on the oxidative burst and may explain why some patients suffer from severe bacterial infections although the total number of granulocytes is normal.

Adult↗
PubMed2000

Severe hypophosphatemia during hematopoietic reconstitution after allogeneic peripheral blood stem cell transplantation.

A patient suffering from acute myeloid leukemia (FAB M5a) received a PBSC allograft from a matched, related donor. On day 13 after transplantation severe hypophosphatemia (0.21 mmol/l) was first noted which persisted irrespective of intravenous phosphate administration, and within 2 days reached concentrations below 0.13 mmol/l. After repeated phosphate substitution serum phosphate returned to 1.40 mmol/l on day 17. Phosphate in urine, and calcium in serum were recorded as unchanged throughout. Clinical signs and symptoms due to severe hypophosphatemia were not observed except for paresthesia in the lower extremities. The precipitous fall in serum phosphate coincided with hematopoietic reconstitution as reflected by a steep rise in leukocyte count from 0.08 x 109/l on day 10 to 5. 94 x 109/l on day 15 after transplantation. Thus, isolated hypophosphatemia was likely the result of excessive cellular phosphate uptake during hematopoietic reconstitution. Electrolyte monitoring after PBSCT should include serum phosphate to identify the hypophosphatemia associated with hematopoietic recovery.

Adult↗
PubMed2000

Selective expression of trophoblastic hormones by lung carcinoma: neurendocrine tumors exclusively produce human chorionic gonadotropin alpha-subunit (hCGalpha).

Recent findings suggest that glycoprotein- and protein hormones act as local auto/paracrine growth/differentiation factors in normal and malignant tissue. An imbalanced or even selective production of human chorionic gonadotropin-alpha (hCGalpha) by neuroendocrine tumors in various organs has been reported. In this context, the ectopic production of trophoblastic hormones by lung carcinoma has not been investigated systemically. Because the determination of serum levels of hCGalpha are flawed by a number of factors, we designed an immunohistochemical study to precisely assess the comprehensive paraneoplastic auto-/paracrine hormone production by lung carcinoma of various histological types. To this end, 90 patients with primary lung neoplasms (40 neuroendocrine tumors, 29 adenocarcinomas, 20 squamous cell carcinomas, and 1 adenosquamous carcinoma) were analyzed by our well characterized monoclonal antibodies (mabs) against the glycoprotein hormones hCG, and its derivatives hCGalpha, hCGbeta, hCGbeta core-fragment (hCGbetacf), luteinizing hormone (LH, LHbeta), follicle-stimulating hormone (FSH, FSHbeta), and the protein hormones placental lactogen (PL) and growth hormone (GH). Overall, trophoblastic hormone immunoreactivity was found in 31% (28/90) of all lung carcinomas, regardless of histological differentiation. Detailed analysis showed 23% (21/90) hCGalpha-, 7% (6/90) hCGbeta, and 2% (2/90) hCGbetacf-positive cases. The tumors produced neither the intact heterodimer hCG, nor the other placental protein hormones PL-A/B and GH-V, or the hCG-related pituitary gonadotropins FSH/FSHbeta and LH/LHbeta. With regard to histological differentiation, it appeared that neuroendocrine tumors exclusively produced free hCGalpha in a distinct expression pattern depending on histological tumor grade. Thirty-eight percent (15/40) of all neuroendocrine neoplasms were hCGalpha-positive, and marker positivity increased with more mature, highly differentiated tumors (20% of small cell neuroendocrine carcinomas versus 90% of atypical and typical carcinoids). This is in striking contrast not only to trophoblastic malignancies and testicular germ cell tumors, but also to nontrophoblastic tumors, such as gynecological and urothelial malignancies, 60% of which produce hCGbeta and where marker positivity correlates with poor histological tumor differentiation. In conclusion, free hCGalpha, but not hCGbeta, is a useful marker for neuroendocrine differentiation in primary lung tumors. The fact that it is preferentially produced by the differentiated tumor types (carcinoids) points to a putative biological function in these tissues. The few hCGbeta-positive NSCLC must not be confounded with primary mediastinal choriocarcinoma.

Adult↗
PubMed2000

A revised model of platelet aggregation.

In this study we have examined the mechanism of platelet aggregation under physiological flow conditions using an in vitro flow-based platelet aggregation assay and an in vivo rat thrombosis model. Our studies demonstrate an unexpected complexity to the platelet aggregation process in which platelets in flowing blood continuously tether, translocate, and/or detach from the luminal surface of a growing platelet thrombus at both arterial and venous shear rates. Studies of platelets congenitally deficient in von Willebrand factor (vWf) or integrin alpha(IIb)beta(3) demonstrated a key role for platelet vWf in mediating platelet tethering and translocation, whereas integrin alpha(IIb)beta(3) mediated cell arrest. Platelet aggregation under flow appears to be a multistep process involving: (a) exposure of vWf on the surface of immobilized platelets; (b) a reversible phase of platelet aggregation mediated by the binding of GPIbalpha on the surface of free-flowing platelets to vWf on the surface of immobilized platelets; and (c) an irreversible phase of aggregation dependent on integrin alpha(IIb)beta(3). Studies of platelet thrombus formation in vivo demonstrate that this multistep adhesion mechanism is indispensable for platelet aggregation in arterioles and also appears to promote platelet aggregate formation in venules. Together, our studies demonstrate an important role for platelet vWf in initiating the platelet aggregation process under flow and challenge the currently accepted view that the vWf-GPIbalpha interaction is exclusively involved in initiating platelet aggregation at elevated shear rates.

Animals↗
PubMed2000

Multicenter phase II study of oral idarubicin in treated and untreated patients with B-chronic lymphocytic leukemia.

Idarubicin is the first anthracycline that can be administered orally facilitating antineoplastic chemotherapy at an improved quality of life. In different studies idarubicin has proved clinical effectiveness in patients with advanced low grade non Hodgkin's lymphoma. We performed a phase II study in 19 patients with untreated and pretreated B-CLL of Binet stage A-C. Idarubucin was administered orally at a dose of 15 mg/m2 over 3 days every 4 weeks. Of 19 evaluable patients (m:f, 16:3, median age 64 years, range 41-80 years) 7 were previously untreated while 12 patients had received prior therapy with fludarabine, chlorambucil or similar non-anthracycline containing regimens. 12 pts had Binet stage C, 5 Binet stage B and 2 Binet stage A. Five patients achieved a partial remission (26%), 5 patients had stable disease (26%) and 9 patients showed progressive disease (47%), resulting in an overall response of 26% (5/19). There was no correlation of response rate with Binet stages or previous treatment regimens. Treatment associated side effects consisted predominantly of mild nausea and vomiting (26%) as well as minor infections (21%) and diarrhoea (16%). These data demonstrate that oral idarubicin as a single agent is well tolerated but of limited effectiveness in B-CLL. Further studies are needed to assess different doses and schedules of oral idarubucin and to test it in combination with other chemotherapeutic agents.

Administration, Oral↗
PubMed2000

GPV is a marker of in vivo platelet activation--study in a rat thrombosis model.

Thrombin plays a central role in the genesis of thrombotic events and is the most potent known platelet agonist. This enzyme activates platelets by cleaving G-protein coupled protease activated receptors (PARs) and by binding to glycoprotein (GP) Ib. Thrombin also cleaves platelet GPV to liberate a soluble 69 kDa fragment (GPVf1), leaving a 20 kDa fragment (GPVf2) attached to the membrane. The aim of this study was to assess the value of GPV as an in vivo marker of the activation of platelets by thrombin. Newly developed monoclonal and polyclonal antibodies recognizing rat GPVf1 and GPVf2 respectively were used to detect soluble GPV by ELISA and the new NH2-terminus exposed by thrombin using flow cytometry. These assays were employed in a rat thrombosis model designed to trigger thrombin formation in vivo. When thromboplastin (4.8 ml/kg/h) was infused for 30 min, thrombin generation was reflected by a rapid increase in thrombin-antithrombin (TAT) complexes in plasma and by the appearance of GPVf2 at the surface of circulating platelets. Simultaneously, GPVf1 disappeared from the surface of platelets and accumulated as a soluble fragment in plasma, where it was detected by GPV ELISA. These effects were inhibited by pretreatment of the rats with hirudin. Levels of plasma PF4 also increased in this model, but unlike GPV levels which returned slowly (> 2 hours) to baseline, PF4 had a very short half-life. In conclusion, GPV is cleaved by thrombin in vivo, circulates and is a reliable in vivo marker of the activation of platelets by thrombin. Monitoring of GPV levels in rats should be useful to evaluate the effects of antithrombotic and antiplatelet drugs, while further studies will be required to confirm the potential interest of GPV as a marker of thrombotic states in humans.

Animals↗
PubMed1999

[Intestinal lymphoma. A long diagnostic path].

CASE REPORT: We describe the case of a 43-year-old patient with a Burkitt lymphoma in the small intestine, who initially presented with abdominal discomfort, weight loss, constipation and neurological symptoms. DIAGNOSIS: In terms of differential diagnosis other inflammatory and tumorous diseases had to be considered. Non-Hodgkin lymphomas are common malignant afflictions of the GI-tract. The total body tumor burden is the principal determinant of prognosis. Serum lactate dehydrogenase (LDH) level is one parameter that reflects the tumor burden. On the other hand abdominal mass, bone marrow and central nervous system involvement are negative prognostic factors. Lymphomas can invade in the CNS at any time during the course of disease. This is generally associated with a poor prognosis if not treated immediately. TREATMENT: High doses of cyclophosphamid and MTX have been shown successful in the treatment of Burkitt lymphoma. Almost all relapses occur on therapy or shortly after termination of treatment. Therefore, criteria are needed to select patients of higher and lesser risk to protect the latter from the further intensification of therapy.

Adult↗
PubMed1999

Detection of residual aneuploid leukemic cells by "continuous gating".

BACKGROUND: A new method for the detection of residual aneuploid leukemic cells in bone marrow by flow cytometry is described. This method is based on the analysis of FCM derived list-mode-datasets with a new software called "Continuous Gating". The program is able to decrease the detection level of aneuploid tumor cells by analyzing groups of cells with comparable antigen density and scatter properties. METHODS: Aneuploid acute lymphocytic leukemia cells with a known CD34 expression were diluted with diploid bone marrow cells to a concentration of 10, 1, 0.1, 0.05, and 0.01%. Each sample was measured in a FACScan flow cytometer, after staining with CD34 Moab and propidium iodide. Listmode-data were analyzed with the new "Windows"-based "Continuous Gating" software. A gate was set in the DNA parameter, defining the channels in which the aneuploid G0/G1-peak of possible residual tumor-cells should be found. Ten thousand overlapping gates of size 200 x 200 channels (out of 1,023 x 1,023 channels) were set automatically by the program into the side-scatter (SSC)/CD34 dot-plot, calculating the percentage of aneuploid G0/G1-phase cells for every specific gate. RESULTS: The results are plotted in a contour-plot. In dot-plot gates with less than 20 cells, the calculation of the percentage of aneuploid cells was declared invalid and the area in the contour-plot was marked. Detection of residual aneuploid cells, based on a defined expression of CD34 and granularity (SSC), was possible down to a contamination of 0.1%. CONCLUSIONS: The new "Continuous Gating" software can be used for the automated detection of aneuploid leukemic cells, if the density of a certain surface-marker is slightly different from normal cells.

Adult↗
PubMed1999

[Treatment of adult acute lymphoblastic leukemia].

In patients with adult ALL, substantial progress has been made in the past 20 years. At present a cure rate of 30-40% can be achieved and varies in defined subgroups between 10-51%. ALL does not represent an uniform disease but is formed by biologic subentities, which differ in their natural history, clinical presentation and prognosis. A comprehensive diagnostic examination, including morphology, cytochemistry, immunology, cytogenetic and molecular genetic analysis is a precondition for prognostic assessment and therapeutic stratification. The basic principle of ALL treatment is a combination chemotherapy with sequential administration of induction, consolidation and maintenance therapy. Bone marrow transplantation has become an important part of the treatment strategy and is performed in patients with high risk. In the subgroup of T-ALL a significant progress has been made in the last years with survival rates of 40-50%. In B-ALL the results have been greatly improved to 48-51% by introduction of a specific treatment strategy. However, the results (about 30%) stagnate for the total group of B-lineage-ALL (common ALL, pre-B-ALL, pro-B-ALL). Patients with B-lineage-ALL can be subdivided in a high and low risk group according to the presence of risk factors (age, white blood cell count, time to achieve a complete remission, pro-B-ALL and the translocations t[4;11], t[9;22]). The outcome of the subgroup of adult pro-B-ALL has been substantially improved (50%). An increase of treatment results (20%) appears in outlines for patients above 50 years. The Ph/bcr-abl positive ALL has in spite of improved complete remission rates (60-70%) consistently unfavourable survival rates (10%).

Adult↗
PubMed1999

Antithrombotic effects of (n-3) polyunsaturated fatty acids in rat models of arterial and venous thrombosis.

The antithrombotic effects of dietary lipids were investigated in rat models of arterial and venous thrombosis. In the arterial model, thrombus formation was evaluated by determination of the occlusion time and the deposition of 111In-labeled platelets and 125I-labeled fibrinogen in a collagen-coated glass capillary inserted into an arterio-arterial shunt. Venous thrombosis was evaluated by measurement of the thrombus weight after administration of thromboplastin as a source of tissue factor and establishment of stasis in the vena cava. Diets were supplemented with saturated (SAT group) or (n-3) fatty acids, the latter being added either as MaxEPA oil (MaxEPA group), or as docosahexaenoic (DHA group) or eicosapentaenoic (EPA group) ethyl ester. Only the MaxEPA group displayed a prolonged occlusion time as compared with all other groups. Platelet accumulation, similar in the MaxEPA, EPA and DHA groups (13.3, 16.7 and 17.7 x 10(6) platelets/shunt, respectively), was significantly higher in the SAT group (25.3 x 10(6) platelets/shunt), while accumulation of fibrinogen-fibrin was similar whatever the group. There was a trend towards a lower venous thrombus weight in MaxEPA fed rats relative to those fed other diets. Our data indicate that the MaxEPA diet had antithrombotic effects in arterial and to a lesser extent venous thrombosis models, best attributed to its multiple targeting of platelets and coagulation.

Animals↗
PubMed1999

Optimized preoperative planning of calcaneal fractures using spiral computed tomography.

The aim of this study was the evaluation of spiral-CT examinations in preoperative planning of calcaneal fractures supported by 3D reconstructions after electronic disarticulation. We examined 45 patients with 47 calcaneal fractures with diagnostic spiral-CT examinations in a prospective study. In addition to the conventional axial slices and sagittal reconstructions, 3D reconstructions prior to and after electronic disarticulation were performed and rated by orthopaedic surgeons and radiologists. The following diagnostic criteria were rated: involvement of articular facets, number of fragments and hindfoot deformities. Axial slices were considered to be the gold standard, because not all patients underwent surgical treatment. Axial slices showed involvement of 90 articular facets (100 %). Three-dimensional reformations after electronic disarticulation depicted 82 fractures (82 of 90, 91 %), sagittal reconstructions 63 fractures (63 of 90, 70 %). Three-dimensional reconstructions without electronic disarticulation showed five fractures (5 of 90, 5.5 %). The number of fragments was demonstrated best on sagittal reconstructions (two, three or four fragments); five fragments were diagnosed best on axial slices, and 3D reconstruction without electronic disarticulation showed only a very small number of fragments, due to overlaying bones. Hindfoot deformities (lateralisation, varus deformation, shortening) were demonstrated best on axial slices, except in terms of showing height reduction, which was demonstrated better on sagittal and 3D reconstructions. Three-dimensional reconstructions after electronic disarticulation support a clear understanding of the 3D position of the fragments and of their displacement in comparison with 3D reconstruction without electronic disarticulation, which is essential for an effective surgical reduction. Due to the potential manipulation of surface-oriented 3D reconstructions, regardless of whether electronic disarticulation is used, this imaging technique should not be considered in an isolated framework. Three-dimensional images without electronic disarticulation are superfluous in any case.

Calcaneus↗