Search PubMed⌕ Search

Biomedical subjects

N Schmitz

Publications and source records attributed to N Schmitz.

At least 55 records · Page 3Linked to original sources
PubMed2001

Event-by-event fluctuations of the Kaon-to-Pion ratio in central Pb+Pb collisions at 158 GeV per nucleon.

We present the first measurement of fluctuations from event to event in the production of strange particles in collisions of heavy nuclei. The ratio of charged kaons to charged pions is determined for individual central Pb+Pb collisions. After accounting for the fluctuations due to detector resolution and finite number statistics we derive an upper limit on genuine nonstatistical fluctuations, which could be related to a first- or second-order QCD phase transition. Such fluctuations are shown to be very small.

Journal Article↗
PubMed2001

The motion aftereffect: more than area V5/MT? Evidence from 15O-butanol PET studies.

The motion aftereffect is a perceptual phenomenon which has been extensively investigated both psychologically and physiologically. Neuroimaging techniques have recently demonstrated that area V5/MT is activated during the perception of this illusion. The aim of this study was to test the hypothesis if a more broadly distributed network of brain regions subserves the motion aftereffect. To identify the neuronal structures involved in the perception of the motion aftereffect, regional cerebral blood flow (rCBF) measurements with positron emission tomography were performed in six normal volunteers. Data were analysed using SPM96. The motion-sensitive visual areas including area V5/MT were activated in both hemispheres. Additionally, the lateral parietal cortex bilaterally, the right dorsolateral prefrontal cortex, the anterior cingulate cortex and the left cerebellum showed significant increases in rCBF values during the experience of the waterfall illusion. In a further reference condition with identical attentional demand but no perception of a motion aftereffect elevated rCBF were found in these regions as well. In conclusion, our findings support the notion that the perceptual illusion of motion arises exclusively in the motion-sensitive visual area V5/MT. In addition, a more widespread network of brain regions including the prefrontal and parietal cortex is activated during the waterfall illusion which represents a non-motion aftereffect-specific subset of brain areas but is involved in more basic attentional processing and cognition.

Adult↗
PubMed2001

High-dose therapy and autologous stem-cell support for chemosensitive transformed low-grade follicular non-Hodgkin's lymphoma: a case-matched study from the European Bone Marrow Transplant Registry.

PURPOSE: To assess the outcome of high-dose therapy with autologous stem-cell support in patients with histologic transformation of low-grade follicular non-Hodgkin's lymphoma (NHL) and identify significant prognostic factors, as well as to compare survival of these patients with that of patients with matched low-grade and de novo high- or intermediate-grade NHL undergoing the same procedure. PATIENTS AND METHODS: Fifty patients with transformed low-grade NHL have been reported to the European Bone Marrow Transplant registry. Outcome from high-dose therapy and significant prognostic factors were analyzed. Their survival was also compared with that of 200 patients with matched low-grade NHL and 200 patients with matched de novo high- or intermediate-grade NHL by a case-matched analysis. RESULTS: The procedure-related death rate among the 50 transformed NHL patients was 18%. Overall survival (OS) and progression-free survival (PFS) rates were 51% and 30% at 5 years, respectively. Median PFS time was 13 months. Raised lactate dehydrogenase levels at transformation (P =.0031) was identified as the only adverse significant predictor of PFS on multivariate analysis. A subgroup of patients with residual chemosensitive disease who attained complete remission after high-dose therapy had the best outcome, with an OS at 5 years of 69%. A comparison with matched patients with low-grade disease and with de novo high- or intermediate-grade lymphoma showed no significant difference in OS (P =.939 and P =.438, respectively). CONCLUSION: Patients with chemosensitive transformed lymphoma should be seriously considered for high-dose therapy and autologous stem-cell support.

Adult↗
PubMed2001

Comparison of incisor mobility after insertion of canine-to-canine lingual retainers bonded to two or to six teeth. A clinical study.

BACKGROUND: Fixed appliance therapy often extends over several years. Debonding is warmly welcomed and is often seen by the patient as the end of treatment. Yet both patients and parents often underestimate the importance of the subsequent retention period and the speed at which negligence in this treatment phase results in relapse. Bonded retainers guarantee excellent long-term stability at least while they are in situ. The reliable attachment of lingual retainers with modern bonding techniques has led to widespread application of this retention method. The present study investigated its influence on tooth mobility and on the damping properties of the periodontal tissue, by means of a dynamic measuring method (Periotest). PATIENTS AND METHOD: For this purpose two groups with mandibular bonded retainers and one control group were formed. The control group wore removable retention appliances. In all groups, active treatment with fixed appliances had been completed at least half a year before baseline. RESULTS: The results showed that bonded retainers had a negative impact on the damping properties of the periodontal tissue and thus in the broader sense on tooth mobility. Tooth mobility decreased with the number of teeth to which the retainer was bonded but remained, as in the control group, within the physiologic range.

Adolescent↗
PubMed2001

A prototype high-resolution animal positron tomograph with avalanche photodiode arrays and LSO crystals.

To fully utilize positron emission tomography (PET) as a non-invasive tool for tissue characterization, dedicated instrumentation is being developed which is specially suited for imaging mice and rats. Semiconductor detectors, such as avalanche photodiodes (APDs), may offer an alternative to photomultiplier tubes for the readout of scintillation crystals. Since the scintillation characteristics of lutetium oxyorthosilicate (LSO) are well matched to APDs, the combination of LSO and APDs seems favourable, and the goal of this study was to build a positron tomograph with LSO-APD modules to prove the feasibility of such an approach. A prototype PET scanner based on APD readout of small, individual LSO crystals was developed for tracer studies in mice and rats. The tomograph consists of two sectors (86 mm distance), each comprising three LSO-APD modules, which can be rotated for the acquisition of complete projections. In each module, small LSO crystals (3.7 x 3.7 x 12 mm3) are individually coupled to one channel within matrices containing 2x8 square APDs (2.6 x 2.6 mm2 sensitive area per channel). The list-mode data are reconstructed with a penalized weighted least squares algorithm which includes the spatially dependent line spread function of the tomograph. Basic performance parameters were measured with phantoms and first experiments with rats and mice were conducted to introduce this methodology for biomedical imaging. The reconstructed field of view covers 68 mm, which is 80% of the total detector diameter. Image resolution was shown to be 2.4 mm within the whole reconstructed field of view. Using a lower energy threshold of 450 keV, the system sensitivity was 350 Hz/MBq for a line source in air in the centre of the field of view. In a water-filled cylinder of 4.6 cm diameter, the scatter fraction at the centre of the field of view was 16% (450 keV threshold). The count rate was linear up to 700 coincidence counts per second. In vivo studies of anaesthetized rats and mice showed the feasibility of in vivo imaging using this PET scanner. The first LSO-APD prototype tomograph has been successfully introduced for in vivo animal imaging. APD arrays in combination with LSO crystals offer new design possibilities for positron tomographs with finely granulated detector channels.

Animals↗
PubMed2001

Allogeneic transplantation of blood stem cells: coming of age?

Mobilized peripheral blood progenitor cells (PBSC) are increasingly being used instead of bone marrow for allogeneic transplantation. The purpose of the present article is to give a concise and clinically oriented overview on current results and perspectives of allogeneic peripheral blood stem cell transplantation, with particular focus on reconstitution of hematopoiesis and the immune system, graft-versus-host disease, graft-versus-leukemia effects, intensity-reduced conditioning, and graft engineering.

Graft vs Host Disease↗
PubMed2001

Autologous stem cell transplantation for follicular lymphoma: no benefit for early transplant?

Autologous stem cell transplantation (SCT) is widely used as salvage treatment for patients with relapsed follicular lymphoma (FL). Although SCT can induce prolonged remissions, it does not appear to be curative in the vast majority of patients. The purpose of this study was to investigate if incorporation of SCT into first-line therapy can improve its efficacy. Fifty-five patients underwent sequential high-dose therapy as up-front (n=33) or salvage treatment (n=22) for advanced stage FL at our institution. Treatment consisted of intensive chemotherapy with dexamethasone, carmustine (BCNU), etoposide, cytarabine, and melphalan (Dexa-BEAM) for mobilization of peripheral stem cells and reduction of tumor load, followed by one of three different myeloablative regimens and SCT. With a median follow-up of 4 years, projected event-free survival (EFS) and overall survival (OS) at 4 years post transplant was 59% and 84%, respectively, with no evidence of plateau in the survival curves. By univariate and multivariate analysis weighing age, sex, stage, BM and extranodal involvement, timing of transplant, ex vivo purging, and conditioning regimen [total body irradiation (TBI) vs non-TBI], the only significant factor predicting for superior EFS and OS was up-front vs salvage transplant (4-year EFS 76% vs 38%, p=0.02; 4-year OS 92% vs 73%, p=0.033). However, when calculated from diagnosis, EFS and OS of the up-front and salvage groups were virtually identical, implying that the longer survival post SCT in the up-front group was completely compensated by the longer interval between diagnosis and transplant in the salvage group. Median OS from diagnosis was 13.5 years. Except for one case of anaplastic large cell lymphoma, secondary neoplasms have not occurred to date. In conclusion, our data indicate that SCT might improve the prognosis of patients with disseminated FL, although it is probably not curative even if applied early during the course of the disease. The optimum timing of SCT remains to be determined by the ongoing randomized multicenter trial of the German Low-grade Lymphoma Study Group. The impact of radiotherapy on the success of SCT does not seem to be as essential as originally believed.

Adult↗
PubMed2001

Cardiovascular reactions induced by unpredictable, predictable, and controllable painful stimuli during sphygmomanometry.

Sphygmomanometry is the most common technique of blood pressure (BP) determination. In order to study effects of predictability and controllability in sphygmomanometric BP measurements, 72 normotensive healthy subjects were examined. BP was determined continuously and non-invasively using a Finapres device (Penaz-technique) and by sphygmomanometry. Five sphygmomanometric measurements took place, during the fourth the arm cuff was inflated to 300 mmHg, the others were done with a pressure of 175 mmHg. Subjects were randomly assigned to one of three groups: In one group the recordings were unpredictable to the subject, in the second group measurements were announced 1 min before cuff inflation took place, and in the third group, subjects could decide when the sphygmomanometric recordings should occur. With unpredictable measurements systolic and diastolic BP decreased (approx. 5 mmHg). When sphygmomanometric recordings were controllable or predictable to the subject BP remained relatively stable. We would suggest that automatic BP devices (e.g. in ambulatory BP monitoring) should generally work with acoustic signals, making cuff inflation predictable for the subject.

Acoustic Stimulation↗
PubMed2001

Dose escalation of cytotoxic drugs using haematopoietic growth factors: a randomized trial to determine the magnitude of increase provided by GM-CSF.

BACKGROUND: The magnitude of chemotherapy dose escalation made possible by the use of recombinant haematopoietic growth factors has not been quantified in a randomized trial. PATIENTS AND METHODS: Patients with refractory or relapsing Hodgkin's disease were randomized to receive the Dexa-BEAM regimen with escalating etoposide doses supported by placebo or granulocyte-macrophage colony-stimulating factor (GM-CSF). Using an adaptive sampling method independently in both arms, the etoposide dose was escalated until the maximal tolerated dose for the first cycle was reached. RESULTS: Thirty patients were randomized to GM-CSF and thirty to placebo. The etoposide dose could be escalated considerably in both treatment arms. Maximal etoposide dose for the first cycle was 1920 mg/m2 for patients receiving GM-CSF and 1160 mg/m2 for patients receiving placebo (P = 0.045 one-sided), corresponding to a 65% higher etoposide dose and a 13% higher dose intensity with GM-CSF. Dose-limiting events were similar in both arms, consisting mainly of prolonged neutropenia and consecutive infections. Treatment efficacy was not different in the two treatment groups. CONCLUSIONS: While GM-CSF permits a somewhat higher dose escalation than placebo, the increase in dose intensity provided by GM-CSF is small. The use of CSF for interval reduction rather than dose escalation is the more effective strategy for dose intensification.

Adolescent↗
PubMed2001

Transfer of idiotypic protein primed allogeneic marrow grafts elicits potent graft-versus-myeloma effects in mice.

The active immunization of bone marrow (BM) donors with myeloma immunoglobulin (Ig) results in an idiotypic T cell response that can be transferred to the recipient. Using a murine model we evaluated the effectiveness, side-effects and underlying mechanisms of this approach. Balb/c (H-2d) mice were given a dose of HOPC-1F myeloma cells secreting the monoclonal IgG2a followed by lethal total body irradiation (7.5 Gy) 2 days later and a subsequent transplantation of 2 x 10(7) allogeneic MHC-matched DBA/2-derived marrow cells. Donors were pre-immunized with three i.p. injections of HOPC(IgG2a) or control Ig given with incomplete Freund's adjuvants (IFA) spaced 1 week apart. In some experiments, donor-spleen cells were additionally transferred 2 h post transplant. Injection of HOPC-myeloma led to death of all animals after a median survival time (MST) of 42 days. A lethal dose of TBI followed by transfer of unmanipulated marrow grafts plus splenocytes resulted in moderate antimyeloma effects with 8% of mice achieving long-term survival. Nearly the same results were obtained after transplantation of BM immunized with the control Ig. In contrast, transplantation of marrow grafts from HOPC(IgG2a) immunized donors exerted a significant GVM effect with 63% long-term survival for more than 180 days. The additional transfer of 2 x 10(7) immune splenocytes derived from the same donor resulted in even stronger anti-myeloma effects (FFR 87%). No increase in the incidence of severe acute GVHD was observed. In vitro data suggest that allogeneic CD8+ idiotype-specific T cells may be the major effector cells. Our results demonstrate that active immunization of the donor with the myeloma-specific Ig can induce powerful graft-versus-myeloma effects after allogeneic BMT.

Animals↗
PubMed2001

Peripheral blood stem cell donation: an analysis from the International Bone Marrow Transplant Registry (IBMTR) and European Group for Blood and Marrow Transplant (EBMT) databases.

Donation-related data for 1488 allogeneic peripheral blood stem cell (PBSC) transplants reported to the International Bone Marrow Transplant Registry (IBMTR) or the European Blood and Marrow Transplant Group (EBMT) by 152 teams worldwide between 1994 and 1998 were reviewed. In 1998, 26% of allografts registered with the IBMTR were collected from blood. Median age of PBSC donors was 38 years (range <1-76), and 55% were male. Of 1486 donor-recipient pairs evaluable for HLA compatibility, 1322 (89%) were HLA-identical siblings. Recombinant human granulocyte colony-stimulating factor (G-CSF) was employed to mobilize PBSCs in almost all (99%) cases. One hundred and seventy (20%) of 828 evaluable PBSC donors had a central catheter placed for leukapheresis. Eighty-five percent of 1321 evaluable PBSC grafts were collected with one or two leukaphereses. There were 15 reported donation-related adverse events (1% of evaluable donors). Complications were catheter-related in five. No donation-related fatalities were reported. These data suggest that PBSC donation is becoming more prevalent worldwide. It appears to have a safety profile comparable to marrow harvesting, although experience with the latter is much more extensive.

Adolescent↗
PubMed2001

Graft-vs-leukemia activity and graft-vs-host disease induced by allogeneic Th1- and Th2-type CD4+ T cells in mice.

INTRODUCTION: The transfer of allogeneic lymphocytes contained in a hematopoietic stem cell graft confers an immune-mediated antileukemic effect, termed the graft-vs-leukemia (GVL) effect. Graft-vs-host disease (GVHD), the most detrimental complication of allogeneic BMT, largely resides within the same lymphocyte population. Therefore, separation of GVL- and GVH-reactions is a long-standing goal of experimental studies dealing with allogeneic transplantation of hematopoietic stem cells. MATERIALS AND METHODS: The objective of the current study was to assess the potential of Th1- and Th2-type CD4+ T cells in mediating GVHD and GVL effects in a fully allogeneic murine transplant model. BALB/c (H-2d) mice were given a dose of A20 (H-2d, B-cell leukemia) cells two days prior to lethal total body irradiation (TBI) and transplantation of fully mismatched (C57BL/6, H-2b) T-cell depleted (anti-Thy1.2, CD90) bone marrow (TCD-BM) cells. Graded numbers of either unmanipulated, Th1- or Th2-polarized highly enriched CD4+ donor type T cells (10(6) or 10(7)) were administered 2 h posttransplant. Infusion of 10(6) of unmanipulated, Th1-, or Th2-primed CD4+ T cells resulted in moderate GVHD-related mortality (40%, 50%, 10%) and significantly improved long-term survival (50%, 45%, 46% surviving the observation period of 120 days) as compared to animals receiving TCD-BM alone (18%). RESULTS: The administration of 10(7) unmanipulated or Th1-type CD4+ T cells given shortly after transplantation led to death of all mice within 50 days due to fatal acute GVHD. In contrast, the adoptive transfer of 10(7) Th2-primed CD4+ T cells resulted in significant improvement of long-term survival (80%) compared to the TCD-BM group. This powerful GVL effect was associated with a substantially lower incidence of lethal acute GVHD (10%) if compared to the results of transplantation of Th1-type CD4+ T cells. CONCLUSION: These results demonstrate that allogeneic Th2-type CD4+ T cells given post BMT can induce GVL effects in a cell-dose-dependent manner without increasing the risk of severe acute GVHD.

Adoptive Transfer↗
PubMed2001

[Factoral structure and psychometric properties of the German version of the Toronto Alexithymia Scale (TAS-20) in psychosomatic patients].

The present paper describes the attempt to cross-validate the three-factorial structure of the German Version of the 20-Item Toronto Alexithymia Scale in a population of 419 patients, suffering of psychogenic disorders. However, results neither revealed good internal consistencies nor was it possible to obtain an acceptable adaptation of the empirical data on the postulated model. Therefore an explorative factor analysis was performed in order to get a more consistent factor model. The hereby resulting four-factorial structure was congruent with reference to theoretical and empirical data of Alexithymia. However, additional cross-validation in other populations has to be investigated.

Adult↗
PubMed2001

Rituximab in autologous stem cell transplantation for follicular lymphoma.

Contamination of stem cell harvests with residual tumor cells is a significant problem hampering the success of autologous peripheral blood stem cell transplantation in non-Hodgkin's lymphoma (NHL). Techniques have therefore been introduced to attempt to remove these cells, either in vivo, prior to harvesting, or ex vivo, before reinfusion into the patient. Rituximab is a human-mouse chimeric anti-CD20 monoclonal antibody that has been administered to patients prior to stem cell harvesting, to purge the blood of residual malignant cells. Clinical studies have shown that rituximab is safe to use during stem cell mobilization since administration did not adversely affect the yield of CD34+ stem cells or the functional capability of these progenitors. Rituximab was also effective in purging stem cell harvests of malignant cells. Translocation of the bcl-2 gene was found in a significantly smaller proportion of stem cell harvests from patients who had received a purging infusion of rituximab than controls. Rituximab may also be useful as salvage therapy following post-transplant relapse or as maintenance therapy for patients in remission. Prospective randomized trials will ultimately define the role of rituximab in the autologous transplantation setting.

Antibodies, Monoclonal↗
PubMed2001

[Metastatic gastric calcifications and bronchial neuroendocrine tumor].

We report the case of a 38 year-old man admitted for the treatment of a neuroendocrine carcinoma of the lung with multiple bone metastases. At the diagnosis, the serum biochemistry revealed an evidence of malignant hypercalcemia with acute renal impairment. At this point, a Tc 99-m MDP bone scan was performed and showed intense uptake throughout the gastric walls. The patient underwent a repeat bone scan after normalization of biochemistry; no more abnormal uptake was noted in the stomach. Hypercalcemia is an abnormality of the calcium metabolism frequently associated with malignant condition. Metastatic calcification results from increased accumulation of the calcium-phosphate salts in different tissues related to a local physiological alcalinity. Usually reversible, metastatic calcifications appear as various extraskeletal uptake at Tc 99-m MDP bone scan.

Adult↗
PubMed2000

Impaired binding of perforin on the surface of tumor cells is a cause of target cell resistance against cytotoxic effector cells.

Exocytosis of perforin, subsequent binding of perforin to the target cell membrane, and formation of lytic pores form an important pathway involved in the induction of tumor cell death by cytotoxic effector cells. Here we describe a novel escape mechanism employed by tumor cells to protect themselves from granule-mediated cell death: We were able to demonstrate that the resistance of the human leukemia cell line ML-2 to natural killer (NK)-cell-mediated killing is not caused by impaired NK-cell activation but by resistance against effector molecules contained in the granules of cytotoxic cells. No resistance was observed against other pore-forming agents like complement and streptolysin O. By using the NK-susceptible leukemia cell line K562, we could show that the induction of cell death by cytotoxic granules can be blocked completely by anti-perforin antibodies, indicating that perforin is essentially involved in this process. Flow cytometric data revealed that an impaired binding of perforin on the tumor cell membrane is mainly responsible for target cell resistance, because perforin turned out to bind well on K562 cells but is not able to attach to the surface of ML-2 cells. After impaired binding of perforin was identified as a potential mechanism of tumor cell resistance, leukemia cells from 6 patients with acute myeloid leukemia (AML) were examined. As predicted, AML cells that failed to bind perforin on their surface demonstrated complete resistance toward NK-cell-mediated cytotoxicity. Thus, perforin resistance could represent an important tumor escape mechanism that should be considered when cytotoxic effector cells are used for cellular immunotherapy. (Blood. 2000;96:594-600)

Bacterial Proteins↗
PubMed2000

Inducible costimulator protein (ICOS) controls T helper cell subset polarization after virus and parasite infection.

It has been shown that certain pathogens can trigger efficient T cell responses in the absence of CD28, a key costimulatory receptor expressed on resting T cells. Inducible costimulator protein (ICOS) is an inducible costimulator structurally and functionally related to CD28. Here, we show that in the absence of CD28 both T helper cell type 1 (Th1) and Th2 responses were impaired but not abrogated after infection with lymphocytic choriomeningitis virus (LCMV), vesicular stomatitis virus (VSV), and the nematode Nippostrongylus brasiliensis. Inhibition of ICOS in CD28-deficient mice further reduced Th1/Th2 polarization. Blocking of ICOS alone had a limited but significant capacity to downregulate Th subset development. In contrast, cytotoxic T lymphocyte (CTL) responses, which are regulated to a minor and major extent by CD28 after LCMV and VSV infection, respectively, remained unaffected by blocking ICOS. Together, our results demonstrate that ICOS regulates both CD28-dependent and CD28-independent CD4(+) subset (Th1 and Th2) responses but not CTL responses in vivo.

Animals↗