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Biomedical subjects

M U Heim

Publications and source records attributed to M U Heim.

At least 19 recordsLinked to original sources
PubMed2002

Platelet concentrates derived from buffy coat and apheresis: biochemical and functional differences.

Today, platelet concentrates are generally produced from whole blood by differential centrifugation (buffy coat-derived platelet concentrates--PCs) or by plateletpheresis (apheresis-derived platelet concentrates--APCs). As PCs are characterized by a lower number of platelets than APCs, four to six PCs are customarily combined in order to obtain an equivalent dose. In the 1970s and 1980s, the use of PCs exceeded that of APCs by far; in contrast, since the beginning of the 1990s, APCs comprise more than half of all transfused platelets. However, the selection of PCs or APCs for transfusion to thrombocytopenic patients is still a matter of debate. The present paper compares biochemical and functional properties of both platelet preparations in vitro. Besides plasma parameters (e.g. platelet factor 4 (PF4), P-selectin, C3a-desarginin, plasma coagulation factors), platelet function was analysed by aggregometry and the PFA 100 system. APCs are characterized by a better preservation of ADP and collagen-induced platelet aggregation, and shorter closure times of the PFA 100 test system during storage. The improved primary in vitro haemostatic capacity of APCs is presumed to be owing to a lower cellular activation rate in these preparations. This hypothesis is supported by the higher plasma concentrations of PF4, beta-thromboglobulin and P-selectin found in PCs compared with APCs. The concentrations of C3a-desarginin in PCs exceed those in APCs by far. Additionally, thrombin generation is higher in PCs than in APCs. These data suggest that APCs are characterized by a superior haemostatic capacity over PCs in vitro. However, in vivo studies should be performed to confirm these findings in the patients' circulation also.

Biomarkers↗
PubMed1999

Standardization of the PFA-100(R) platelet function test in 105 mmol/l buffered citrate: effect of gender, smoking, and oral contraceptives.

The PFA-100(R) (PFA) diagnostic system for the detection of platelet dysfunction was evaluated to determine reference ranges in a normal population. The PFA determines the primary haemostasis capacity (PHC) of anticoagulated whole blood, expressed by the system's closure time (CT). In this study the CT reference ranges were determined for blood samples collected in 105 mmol/l (3.2%) buffered citrate and the effect of gender, smoking, and use of oral contraceptives on reference ranges was assessed. Each of the 309 healthy blood donors from five blood centres was confirmed to have normal platelet function before inclusion in the study. Blood samples were tested in duplicate with both the collagen/epinephrine (Col/Epi) and collagen/ADP (Col/ADP) test cartridges. PFA reference ranges (90% central intervals of measured closure times) for both cartridge types were similar for all groups. Subgroup analysis showed that neither gender nor oral contraceptive usage had any effect on PHC. The 95% cut-off value for the Col/Epi CT was slightly higher for smokers than for non-smokers, an effect more pronounced in female than in male donors. However, the small difference did not justify establishment of specific reference ranges for smokers. Data from all included subjects were pooled to calculate the CT reference ranges for blood samples collected in 105 mmol/l buffered citrate (Col/Epi 82-150 s; Col/ADP 62-100 s). Normal levels of fibrinogen, as well as normal platelet counts and normal haematocrit levels, appeared not to influence the PHC. Because slight but significant differences of the reference ranges were observed between some of the participating sites, in-house confirmation of these reference range guidelines is recommended.

Adolescent↗
PubMed1998

Transforming growth factor beta is increased in plasma of patients with hematologic malignancies after transfusion of platelet concentrates.

BACKGROUND: Transforming growth factor beta 1 (TGF-beta 1) acts as a potent inhibitor of bone marrow proliferation. High concentrations were found in human platelets, which release this cytokine during storage. STUDY DESIGN AND METHODS: TGF-beta 1 levels during a storage period of 5 days were compared in the plasma of platelet concentrates prepared by apheresis or by the buffy coat method. In addition, TGF-beta 1 plasma levels were monitored in patients with hematologic malignancies before and after transfusion. RESULTS: TGF-beta 1 levels in the supernatant of platelet concentrates were found to be 55 times higher than those in the plasma of healthy volunteer donors. During storage, an additional increase was observed. Accordingly, the transfusion of platelet concentrates resulted in a significant increase of plasma TGF-beta 1 levels in patients with hematologic malignancies (before transfusion: 2.2 +/- 0.5 ng/mL; after transfusion: 2.9 +/- 0.6 ng/mL), and these higher levels persisted for at least 4 hours. CONCLUSION: Because TGF-beta 1 reduces the clonogenic capacity of hematopoetic progenitor cells, a myelosuppressive effect of platelet transfusions is suggested.

Adult↗
PubMed1996

[Morphologic and functional changes in thrombocytes after deep freezing with DMSO].

BACKGROUND: During the past decade much work has been carried out towards establishing the optimum method for cryopreservation of platelets. Among the various cryoprotectants dimethyl sulfoxide (DMSO) has been shown to be the most effective. This report describes ultrastructural and functional changes of platelets during the deep-freezing process with DMSO. MATERIALS AND METHODS: Single-donor platelet concentrates were cryopreserved in liquid nitrogen by use of DMSO. Before, during and after the freezing process samples were taken for analysis of ultrastructure and platelet function. RESULTS: While after isolation and addition of DMSO a normal ultrastructure of platelets could be observed, clear signs of beginning cell necrosis were detected after thawing and resuspension in autologous plasma. Fibrinogen-binding capacity and platelet aggregation were significantly diminished. CONCLUSIONS: Although cryopreserved platelets are characterized by hemostatic effects in vivo, it seems conceivable that these effects could be improved by further development of platelet-freezing techniques.

Blood Platelets↗
PubMed1996

[Cryopreservation of erythrocytes: detailed quality control].

It has been well established that cryopreservation of red cells with glycerol is a suitable method for long-time storage. Therefore, many data for quality control have been published. Most measurements, however, are restricted to the final product. Less information is available about the particular steps of cryopreservation. The present paper describes in detail the results of quality control measurements during the procedure. Although the final product meets the demand of the WHO for cryopreserved red cells, it could be demonstrated that erythrocytes are remarkably damaged by the deep-freezing process. Further experiments seem to be necessary in order to improve the details of the deep-freezing procedure.

Blood Preservation↗
PubMed1995

[Leukocyte depletion of blood products. Indications and technical implementation].

Leukocytes contaminating donated blood are considered to be responsible for many of the side effects associated with blood transfusions. These include HLA sensitization and its sequelae, as also graft versus host reaction, transmission of CMV. The present article summarizes the indications for leukocyte depletion and its technical execution.

Blood Component Transfusion↗
PubMed1995

Quality control of platelet concentrates by the Thrombostat 4000.

Quality control of platelet concentrates (PC) is an important prerequisite for good transfusion praxis. However, direct measurement of platelet function is complex, since available methods (e.g. aggregometry, serotonin release) are time consuming and require special equipment. Therefore a test system is needed, which is easy to handle, fast, and achieves reliable results. The present paper compares the results of conventional platelet function tests with those of a modified in-vitro bleeding test (IVBT) (Thrombostat 4000) in liquid-stored and cryopreserved PCs. A high correlation between aggregometry, serotonin release, GMP 140 expression upon stimulation, and IVBT was demonstrated. Therefore IVBT seems to be a good alternative to the conventional platelet function tests for quality control of PCs. In addition, a good correlation between the results of IVBT of patients' blood after PC transfusion and IVBT of patients blood before transfusion supplemented with platelets of the respective PC could be found. Therefore IVBT seems to be able to predict PC transfusion success. However, since these data were obtained in a small sample undergoing bone marrow transplantation, further studies are needed to verify this hypothesis.

Bleeding Time↗
PubMed1995

[Post-transfusion rise in thrombocytes: observations in a hematologic-oncologic patient sample].

OBJECTIVE: Aim of the present analysis was the evaluation of clinical conditions and product-specific parameters influencing posttransfusion platelet increment. DESIGN: 400 single-donor platelet transfusions were analyzed for patient- and concentrate-specific factors influencing posttransfusion platelet increment. Statistical analysis was performed by the General Mixed Model Analysis of Variance. SETTING: Department of hematology and oncology at a university hospital. PATIENTS: 46 patients (24 male, 22 female; age 17-80 years). INTERVENTIONS: Single-donor platelet transfusions. RESULTS: As demonstrated earlier, splenomegaly, body temperature, and bone marrow transplantation could be proven as factors reducing posttransfusion platelet increment. In addition, hepatomegaly and application of antibiotics had negative effects on platelet increment. Among the product-specific parameters leukocyte contamination and pretransfusion storage time reduced transfusion success significantly. CONCLUSIONS: Clinical factors influencing posttransfusion platelet increment can hardly be controlled. In contrast, concentrate-specific parameters can be influenced by preparation technique and storage procedure. Therefore, high value should be set on low leukocyte contamination and short pretransfusion storage time of platelet concentrates.

Adolescent↗
PubMed1994

[Quality control of stored platelet concentrates by means of flow cytometry].

Storage of single-donor platelets is currently limited to 5 days. During this period, however, numerous morphologic and biochemical changes have been observed. The present study describes increased binding of anti-GMP 140 to stored single-donor platelet concentrates; this reveals a progressive activation process. In contrast, when stored platelets are stimulated with ADP, GMP 140, expression is reduced indicating a diminished release reaction. Additionally, the GP IIb/IIIa receptor complex and its fibrinogen-induced binding site (LIBS1) are reduced by storage time, demonstrating a diminished fibrinogen binding. Further experiments have to clarify whether these changes observed in vitro translate into a reduced hemostatic capacity after transfusion in vivo.

Blood Donors↗
PubMed1994

[Post-transfusional platelet increment: effect of clinical factors].

The results of platelet transfusions depend upon a variety of different conditions; besides alloimmunization, a lot of clinical factors are responsible for transfusion success. The present paper tries to work out clinical findings, which are related to successful or unsuccessful platelet transfusions. The following criteria could be identified to influence posttransfusion platelet increment: hepatomegaly, splenomegaly, diagnosis, antibiotics, number and time of previous platelet transfusions. AB0 compatibility, pretransfusion storage time and leucocyte contamination. Therefore, in platelet transfusion therapy a high value should be set on AB0 compatibility, brief storage time and low leucocyte contamination, since these parameters--in contrast to the other influencing factors--can easily be controlled.

Adolescent↗
PubMed1993

[Thrombocyte transfusion. Indications, side effects and problems].

The transfusion of platelet concentrates now represents one of the most common therapeutic measures employed in transfusion medicine. In particular the development of new, aggressive forms of chemotherapy has rapidly increased the need for platelet concentrates over the last few years. The aim of the present study is to describe the major indications and discuss briefly the side effects and problems associated with the transfusion of platelet concentrates.

Blood Group Incompatibility↗
PubMed1993

Storage of single-donor platelet concentrates: metabolic and functional changes.

During the last decade, the trend toward intensifying chemotherapeutic regimens in patients with hematologic malignancies rapidly increased the demand for single-donor platelet concentrates (PCs). The logistics of such supply, however, necessitated the storage of these blood components prior to transfusion. Today, most blood centers use di(2-ethylhexyl)phthalate-free blood bags, which are assumed to allow a storage period of up to 5 days. This report describes biochemical and functional changes of stored single-donor PCs, which may influence the expected quality of PCs. The acid-base status is characterized by an initial respiratory alkalosis compensated by a metabolic acidosis. Changes in extracellular electrolyte, lactate dehydrogenase, glucose, lactate, elastase, and complement levels, as well as in the release of alpha granule content and the initial activation of plasma coagulation, are demonstrated. These changes result in a functional impairment of stored PCs as reflected by thromboxane and serotonin release reaction and by aggregation and in vitro bleeding time studies. In contrast, in vivo recovery and survival rates have been reported to be unaffected. Whether the good recovery and survival rates are caused by a rejuvenescence of stored PCs in vivo or are due to injured circulating platelets has not yet been proven.

Adenosine Diphosphate↗
PubMed1993

[Storage of thrombocyte concentrates: quality control by in vitro bleeding test].

BACKGROUND: The increasing demand for single-donor platelet concentrates necessitates the storage of these blood products prior to transfusion. Quality control of these platelets, however, is still a problem. Most of the available techniques are time-consuming and require sophisticated equipment and specifically trained personnel. The present paper describes a new method for quality control of stored platelet concentrates. MATERIALS AND METHODS: Single-donor platelet concentrates were stored for 7 days; daily aliquots were taken and the in vitro bleeding time (Thrombostat 4000) and platelet aggregation (aggregometer) were determined. RESULTS: The in vitro bleeding test can be handled simply and fast. The results are comparable with those of platelet aggregation tests. CONCLUSION: The in vitro bleeding test provides a good alternative to the conventional methods commonly used for quality control of platelet concentrates.

Bleeding Time↗
PubMed1992

McLeod syndrome: a distinct form of neuroacanthocytosis. Report of two cases and literature review with emphasis on neuromuscular manifestations.

McLeod syndrome was originally described on the basis of a specific blood group phenotype with weak expression of Kell antigens. This erythrocyte abnormality also causes acanthocytosis. The haematological findings are associated with abnormalities in other organ systems, including neuromuscular manifestations. A 51-year-old patient was followed up for 11 years. He presented with persistent muscle creatine kinase elevation and progressive heart disease and later developed a slowly progressive neuropathy and choreic movements. His younger brother presented with grand mal seizures, involuntary movements and high muscle creatine kinase when aged 43 years. Clinical myopathy was absent in both, yet muscle biopsy showed mild myopathic changes. The presence of a motor axonopathy was supported by electrophysiological findings. One brother also showed sensory axonopathy. The movement disorder suggested accompanying basal ganglia dysfunction. Earlier reports of McLeod syndrome are reviewed with respect to neuromuscular involvement. Absence of the Kx membrane protein seems to be the cause of this multi-system disorder.

Acanthocytes↗