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Biomedical subjects

M B Fischer

Publications and source records attributed to M B Fischer.

At least 19 recordsLinked to original sources
PubMed2007

Apheresis products of the Amicus and the AS.TEC 204 cell separators are comparable with regard to dendritic cells derived from the mononuclear cell collection.

BACKGROUND: In this study, we investigated the quality of autologous mononuclear cells (MNC) collected with two different cell separators using standard MNC-apheresis procedure modalities. MNCs were purified by density gradient centrifugation and cultured according to standard protocols to generate dendritic cells (DC) and 1 x 10(7)/ml immature DCs were pulsed with tumour lysate for 3 days and subsequently characterized by fluorescent-activated cell sorter analysis. RESULTS: No difference was found in the monocyte content of either apheresis product (P = 0.07) and in the overall yield of MNCs (P = 0.7). Mature DCs as defined by their phenotype revealed also no significant difference: Amicus, 118 x 10(6) cells +/- 91 vs. AS.TEC 204, 128 x 10(6) cells +/- 137 (P = 0.55), respectively, although the contamination with platelets (threefold) and red cells (twofold) was significantly higher in the AS.TEC 204 group (P < 0.05) than in the Amicus group. CONCLUSION: The Amicus and the AS.TEC 204 are equally capable in providing MNCs for the generation of DCs and the amount of concomitantly collected red cells and platelets had no impact on the final DC yield.

Adult↗
PubMed2006

STRO-1+ mesenchymal precursor cells located in synovial surface projections of patients with osteoarthritis.

OBJECTIVE: To investigate the presence of mesenchymal precursor cells (MPCs) in synovial surface projections of patients with osteoarthritis (OA), to characterize their phenotype and to show their localization. METHODS: Progenitor cells in synovial surface projections were identified by immunohistochemistry, morphometric analysis and confocal laser scanning microscopy using the following phenotypic markers: STRO-1, CD34, and alpha smooth muscle actin (alpha-SMA). RESULTS: In the synovial tissue of all 21 patients with OA MPCs were detected. Immunohistochemistry and subsequent morphometric analysis showed that approximately twice as many STRO-1+ cells/mm2 were observed in synovial tissue of patients with OA as compared to healthy organ donors and that number of STRO-1+ cells/mm2 correlated with total cell number/mm2. Interestingly, in the synovial tissue of patients with OA, twice as many STRO-1+ cells/mm2 were found in synovial surface projections as compared to the sublining area without villi. Using confocal laser scanning microscopy two populations of STRO-1+ MPCs could be detected in synovial surface projections. Single STRO-1+ cells that co-expressed alpha-SMA resemble a population of pericyte precursors required to stabilize the immature vasculature. The second STRO-1+ cell population that was found lacked alpha-SMA but co-expressed CD34 on their surface with low intensity. CONCLUSION: Here we can show that in the synovial tissue of patients with OA twice as many STRO-1+ MPCs can be found in synovial surface projections as compared to the sublining area. These cells are preferentially located at the basis and in the protruding end of the synovial surface projection.

Actins↗
PubMed2004

Proliferation of dental pulp fibroblasts in response to thrombin involves mitogen-activated protein kinase signalling.

AIM: To examine the involvement of mitogen-activated protein kinases (MAPK) signalling on thrombin-stimulated human dental pulp fibroblasts (DPF). METHODOLOGY: Dental pulp fibroblasts were isolated from dental pulp connective tissue of third molars and expanded in vitro. Expression of thrombin receptors was analysed by RT-PCR, and cell proliferation was measured by 3[H]-thymidine incorporation assay. Phosphorylation levels of MAPK were determined by Western blot analysis, and alkaline phosphatase activity was measured to serve as a marker for odontogenic differentiation. Statistical analysis was performed by Student's t-test. RESULTS: Dental pulp fibroblasts express the thrombin receptors protease-activated receptor-1 (PAR-1), PAR-3 and PAR-4. Measurement of 3[H]-thymidine incorporation revealed a dose-dependent increase of DNA synthesis in response to thrombin treatment. The thrombin-induced mitogenic activity was decreased by the extracellular signal-regulated protein kinase (ERK) signalling inhibitor PD98059 (P < 0.05), and by SB203580 (P < 0.05), a p38 MAPK inhibitor. Western blot analysis demonstrated increased phosphorylation of ERK in DPF following stimulation with thrombin, while p38 MAPK and c-Jun NH2-terminal kinase (JNK) were not activated. Alkaline phosphatase activity of DPF remained unchanged upon incubation with thrombin. CONCLUSIONS: These results suggest that signalling via MAPK mediates the mitogenic activity of thrombin on DPF and may thus play a role during the early stages of pulp repair.

Adult↗
PubMed2003

Quality of packed red blood cells and platelet concentrates collected by multicomponent collection using the MCS plus device.

The demand for blood components is constantly increasing, while the exclusion criteria for donors are strengthened in order to reach maximal safety for donors and patients. To counterbalance reduced availability of volunteers, multicomponent collections (MCC) is an attractive approach to produce more than one component during a single apheresis procedure from one donor, such as packed red blood cells (PRBCs) and platelet concentrates (PCs). Further, the exposures of patients to a limited number of donors reduces the possibility of alloimmunization and transfusion-related diseases. We measured the quality of PRBCs and PCs obtained by MCC, using the MCS+ device with the LDPRBC program, Revision B, and compared them with the quality of manually collected PRBCs and PCs collected with the Revision C2 of the MCS+. We found higher pH levels and lower hemolysis assessed by means of fHb and K+ in the supernatant of PRBCs over the whole storage period of 42 days in MCC-derived PRBCs. The functional metabolism assessed by intracellular ATP was higher in PRBCs collected by MCC than in manually collected units. Furthermore, PCs obtained during MCC showed an increase in p-selectin expression on day 5 of storage compared to PCs collected with the Revision C2 of the MCS+. The p-selectin expression on MCC platelets was within the range of p-selectin expression found in PCs obtained by other apheresis devices. These results indicate less storage lesion in MCC-derived PRBCs compared to manually collected units and no compromise in the quality of MCC PCs obtained in the same apheresis procedure.

Adenosine Triphosphate↗
PubMed2002

Platelet-released supernatants stimulate formation of osteoclast-like cells through a prostaglandin/RANKL-dependent mechanism.

Platelets are activated at fracture sites or upon the insertion of implants as a consequence of vascular disruption and secrete the contents of their granules into the developing hematoma. The regeneration of injured tissue requires bone remodeling and the resorbing activity of osteoclasts. To test our hypothesis that platelets can stimulate osteoclastogenesis, we examined the effects of supernatants released from thrombin-activated platelets on osteoclast-like cell formation in murine bone marrow cultures. Histochemical analysis indicated the presence of bone-resorbing, tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells. Transcripts that are characteristically expressed in native osteoclasts were increased in these cultures, as determined by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. The inhibition of both cyclooxygenases with indomethacin, as well as the addition of the cyclooxygenase-2 (COX-2)-selective antagonist, NS398, completely blocked osteoclast-like cell formation and decreased endogenous prostaglandin E(2) production. Platelet-released supernatants stimulated the expression of receptor activator of NF-kappaB ligand (RANKL), whereas mRNA levels of osteoprotegerin (OPG) were decreased. The formation of osteoclast-like cells was prevented by recombinant OPG. Our results suggest that COX-2 activity is necessary for osteoclast-like cell formation in response to platelet-released supernatants, and that endogenously produced prostaglandin E(2) can, in turn, increase the RANKL:OPG ratio, indicating that platelets can contribute to bone remodeling by stimulation of osteoclastogenesis.

Animals↗
PubMed2001

Altered intracellular purine nucleotides in gamma-irradiated red blood cell concentrates.

BACKGROUND AND OBJECTIVES: Gamma irradiation at a dose of 30 Gy induces deterioration of erythrocytes, resulting in storage lesions that significantly shorten the shelf-life of packed red cell concentrates (RCCs). The aim of the present study was to investigate the effect of gamma irradiation on intracellular purine nucleotides of red blood cells during storage. MATERIALS AND METHODS: Three-day-old leucocyte-depleted saline-adenine-glucose-mannitol (SAGM)-preserved RCCs, obtained from the Blood Service of the Austrian Red Cross, were gamma irradiated with 30 Gy. Samples were taken on days 1, 2, 3 and 7 after irradiation and subsequently at weekly intervals up to the end the of shelf-life (day 39 after irradiation) and were investigated for the K+ and Na+ content in the supernatant, for intracellular concentrations of ATP, ADP, ITP, IDP, GTP and GDP of erythrocytes, and for haemolysis. RESULTS: Within the first 24 h after gamma irradiation, no metabolic or biochemical changes were detectable in the RCCs. The K+ concentration in the supernatant increased after 24 h, while the Na+ concentration decreased in irradiated units and this ion disequilibrium persisted until the end of the shelf-life. After an initial increase of intracellular ATP, ADP and GTP during the first week of storage, the intracellular concentrations of ATP, ADP, GTP and ITP decreased, while IDP increased. The decrease of ATP and ADP was found to be more pronounced in irradiated units. At the end of the shelf-life, the ATP, GTP and ITP concentrations of irradiated RCCs had decreased to < 10% of the initial level and the critical threshold of 0.8% haemolysis was reached. CONCLUSION: Gamma irradiation of SAGM-preserved RCCs leads to serious deterioration of the purine nucleotide metabolism of erythrocytes during storage, which can reduce the in vivo recovery of the transfused red cells.

Blood Preservation↗
PubMed2001

Increased serum flt3-ligand in healthy donors undergoing granulocyte colony-stimulating factor-induced peripheral stem cell mobilization.

The effect of granulocyte colony-stimulating factor (G-CSF) induced mobilization of peripheral blood progenitor cells (PBPC) on the endogenous serum levels of cytokines stem cell factor (SCF) and flt3-ligand (flt3-L) was studied in 18 healthy subjects undergoing allogeneic PBPC donation. Donors received a standardized mobilization regime consisting of a 4-day course of G-CSF, with leukapheresis on day 5. Endogenous serum flt3-L and SCF were determined prior to G-CSF administration, on the day of leukapheresis, and followed up until day +100 after cessation of G-CSF administration. The administration of G-CSF resulted in a transient elevation of endogenous flt3-L serum levels. At the day of leukapheresis serum flt3-L showed a median increase of 75% compared to serum flt3-L levels obtained before G-CSF treatment. The increase in serum flt3-L levels showed no correlation with the total number of progenitor cells mobilized. Cessation of G-CSF treatment led to normalization of serum flt3-L within 7 days post G-CSF administration. In contrast, serum CSF levels remained unchanged in response to G-CSF administration. Our results demonstrate a transient surge in serum flt3-L in relation to G-CSF-induced PBPC mobilization, although the assessment of endogenous flt3-L give no information regarding the ability for G-CSF-induced PBPC recruitment in healthy individuals.

Adolescent↗
PubMed2001

Increased expression of the blood group-related Lewis Y antigen on synovial fluid granulocytes of patients with arthritic joint diseases.

OBJECTIVE: To evaluate the expression of the carbohydrate structures Lewis Y (LeY), sialyl-LeX (sLeX) and Lewis X (LeX) on paired peripheral blood (PB) and synovial fluid (SF) granulocytes in patients with arthritic diseases. METHODS: Ten patients with rheumatoid arthritis (RA), seven patients with spondyloarthritis (SA) and eight patients with osteoarthritis (OA) were studied. Granulocyte expression of the Le oligosaccharides was analysed by fluorescence-activated cell sorting. RESULTS: SF granulocytes of patients with RA, SA and OA expressed higher levels of the LeY oligosaccharide than PB granulocytes. Increases in LeY on SF granulocytes were similar in all three underlying diseases. No differences in the expression of the Le antigens were detected between PB granulocytes of patients and healthy individuals. Expression of sLeX and LeX showed no variation between SF and PB neutrophils. CONCLUSION: The selective increase in LeY antigen on SF granulocytes in RA, SA and OA suggests a role of the LeY oligosaccharide in granulocyte traffic and inflammatory responses.

Adult↗
PubMed2000

Binding of disease-associated prion protein to plasminogen.

Transmissible spongiform encephalopathies are associated with accumulation of PrP(Sc), a conformer of a cellular protein called PrP(C). PrP(Sc) is thought to replicate by imparting its conformation onto PrP(C) (ref. 1), yet conformational discrimination between PrP(C) and PrP(Sc) has remained elusive. Because deposition of PrP(Sc) alone is not enough to cause neuropathology, PrP(Sc) probably damages the brain by interacting with other cellular constituents. Here we find activities in human and mouse blood which bind PrP(Sc) and prion infectivity, but not PrP(C). We identify plasminogen, a pro-protease implicated in neuronal excitotoxicity, as a PrP(Sc)-binding protein. Binding is abolished if the conformation of PrP(Sc) is disrupted by 6M urea or guanidine. The isolated lysine binding site 1 of plasminogen (kringles I-III) retains this binding activity, and binding can be competed for with lysine. Therefore, plasminogen represents the first endogenous factor discriminating between normal and pathological prion protein. This unexpected property may be exploited for diagnostic purposes.

Animals↗
PubMed2000

Concurrence of sarcoidosis and aortitis: case report and review of the literature.

Takayasu arteritis (TA) is a rare manifestation of systemic large vessel vasculitis which affects predominantly the aorta and its main branches, but often remains unrecognised owing to delayed diagnosis and non-characteristic clinical features. Sarcoidosis, too, is a systemic inflammatory disease which can affect virtually any organ system. Reports about the coincidence of both diseases have appeared. The case presented here is characterised by a significant time lag between detection of TA and appearance of clinical signs of sarcoidosis. The woman, now 39 years old, had erythema nodosum, circumscript alopecia, and recurrent uveitis, which dated back to 1980 and was attributed to sarcoidosis. At least 12 years later aortic valve insufficiency with progressive cardiac failure developed. Histology performed at the time of aortic valve prosthesis in 1997 disclosed a diagnosis of TA, which was confined to the aortic root. Incidentally, sarcoidosis was diagnosed in adjacent lymph nodes. A thorough check up failed to detect further manifestations of TA; thus, possibly, the patients had aortitis similar to, but not identical with, TA. Several related cases previously reported are discussed, suggesting that both diseases may be inherently related as they are characterised by certain non-specific, immunoinflammatory abnormalities. This case report suggests that the prevalence of TA, or related forms of arteritis, may be higher than expected and should be considered, especially in younger patients with non-characteristic cardiovascular symptoms and suspected systemic inflammatory disease. Moreover, the association with sarcoidosis in this and other previously described cases suggests that the two diseases may be related and that TA or TA-like vasculitis may even be a complication of sarcoidosis.

Adult↗
PubMed1999

Humoral response to herpes simplex virus is complement-dependent.

The complement system represents a cascade of serum proteins, which provide a major effector function in innate immunity. Recent studies have revealed that complement links innate and adaptive immunity via complement receptors CD21/CD35 in that it enhances the B cell memory response to noninfectious protein antigens introduced i.v. To examine the importance of complement for immune responses to virus infection in a peripheral tissue, we compared the B cell memory response of mice deficient in complement C3, C4, or CD21/CD35 with wild-type controls. We found that the deficient mice failed to generate a normal memory response, which is characterized by a reduction in IgG antibody and germinal centers. Thus, complement is important not only in the effector function of innate immunity but also in the stimulation of memory B cell responses to viral-infected cell antigens in both blood and peripheral tissues.

Animals↗
PubMed1998

Enhanced B-1 cell development, but impaired IgG antibody responses in mice deficient in secreted IgM.

The role of endogenous natural IgM in promoting the adaptive Ab response was investigated in newly constructed mutant mice in which B cells do not secrete IgM but still express surface IgM and IgD and undergo class switching to express other Ig isotypes. While the mutant mice had relatively normal numbers of conventional B (B-2) cells in all tissues examined, unexpectedly, B-1 cells in the peritoneum and spleen were approximately threefold more abundant. The elevated levels of B-1 cells were already detectable at 4 wk of age and were stably maintained throughout life. The levels of serum IgG2a, IgG3, and IgA were also elevated in the mutant mice at an early age. IgG2a response to a T cell-independent Ag was augmented, whereas IgG Ab responses to suboptimal doses of a T cell-dependent Ag were impaired. The latter defect was associated with fewer splenic germinal centers, impaired Ab affinity maturation, and less Ag trapping on follicular dendritic cells. Together, these findings demonstrate a physiologic role of natural IgM in the feedback regulation of B-1 cell development, the regulation of IgG2a production, and the promotion of efficient B-2 cell Ab responses.

Animals↗
PubMed1998

Dependence of germinal center B cells on expression of CD21/CD35 for survival.

Affinity-driven selection of B lymphocytes within germinal centers is critical for the development of high-affinity memory cells and host protection. To investigate the role of the CD21/CD35 coreceptor in B cell competition for follicular retention and survival within the germinal center, either Cr2+ or Cr2null lysozyme-specific transgenic B cells were adoptively transferred into normal mice immunized with duck (DEL) or turkey (TEL) lysozyme, which bind with different affinities. In mice injected with high-affinity turkey lysozyme, Cr2null B cells responded by follicular retention; however, they could not survive within germinal centers. This suggests that CD21 provides a signal independent of antigen that is required for survival of B cells in the germinal center.

Adoptive Transfer↗
PubMed1998

Local synthesis of C3 within the splenic lymphoid compartment can reconstitute the impaired immune response in C3-deficient mice.

Mice bearing a disrupted C3 locus (C3-/-) have an impaired Ab response to T-dependent Ags (bacteriophage phiX 174 and nuclear protein-keyhole limpet hemocyanin) characterized by a reduction in number and size of germinal centers and impaired retention of Ag by follicular dendritic cells. To test the importance of C3 synthesized locally within the lymphoid compartment during an immune response to T-dependent Ag, we reconstituted C3-/- mice with wild-type bone marrow of MHC-identical littermates. Engraftment not only restored local C3 synthesis in the spleen, but also rescued the impaired humoral response. The major source of C3 mRNA was MOMA-2+ macrophages localized within the white pulp areas of the spleen. Interestingly, C3 expression is apparently regulated as C3 mRNA was not detected in splenic sections of nonimmune mice. Furthermore, local C3 synthesis by donor macrophages reversed the impaired Ag trapping by splenic follicular dendritic cells in C3-deficient mice.

Animals↗
PubMed1998

Transgenic and knockout mice in research on prion diseases.

Since the discovery of the prion protein (PrP) gene more than a decade ago, transgenetic investigations on the PrP gene have shaped the field of prion biology in an unprecedented way. Many questions regarding the role of PrP in susceptibility of an organism exposed to prions have been elucidated. For example mice with a targeted disruption of the PrP gene have allowed the demonstration that an organism that lacks PrPc is resistant to infection by prions. Reconstitution of these mice with mutant PrP genes allowed investigations on the structure-activity relationship of the PrP gene with regard to scrapie susceptibility. Unexpectedly, transgenic mice expressing PrP with specific amino-proximal truncations spontaneously develop a neurologic syndrome presenting with ataxia and cerebellar lesions. A distinct spontaneous neurologic phenotype was observed in mice with internal deletions in PrP. Using ectopic expression of PrP in PrP knockout mice has turned out to be a valuable approach towards the identification of host cells that are capable of replicating prions. Transgenic mice have also contributed to our understanding of the molecular basis of the species barrier for prions. Finally, the availability of PrP knockout mice and transgenic mice overexpressing PrP allows selective reconstitution experiments aimed at expressing PrP in neurografts or in specific populations of hemato- and lymphopoietic cells. Such studies have shed new light onto the mechanisms of prion spread and disease pathogenesis.

Animals↗