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Biomedical subjects

A Schreiber

Publications and source records attributed to A Schreiber.

At least 37 records · Page 2Linked to original sources
PubMed2000

Osseous lesions of the distal ulna: atypical location--unusual diagnosis. Report of three cases with similar imaging and different pathologic diagnoses.

Three cases with destructive bone lesions of the distal end of the ulna caused by different pathologic entities (Ewing's sarcoma, osteosarcoma, rheumatoid pseudotumoral synovitis) are presented, all with similar clinical and comparable x-ray and magnetic resonance imaging features. Although the distal end of the ulna may be resected without significant functional impairment, careful evaluation of treatment strategies compatible with oncologic standards is warranted.

Adult↗
PubMed2000

Effect of changing the weekly dose intensity of fractionated irradiation on local control of two human squamous cell carcinomas in nude mice.

PURPOSE: To compare the effect of fractionated irradiation with increasing, constant or decreasing weekly dose intensity on local tumour control. MATERIALS AND METHODS: Human squamous cell carcinomas, FaDu and GL, were grown in nude mice. Thirty fractions were applied under ambient conditions with increasing, constant or decreasing weekly dose intensity within a constant overall treatment time of 6 weeks. Dose intensity was changed every 2 weeks. Irradiations were terminated in some groups of animals after 20 fractions in 4 weeks. Endpoint was the tumour control dose 50% (TCD50) at day 120 (FaDu) or day 180 (GL) after end of treatment. RESULTS: In FaDu tumours the TCD50 value of 60 Gy (95% CI 56; 63) for fractionated irradiation with decreasing dose intensity, i.e. high initial doses, was slightly but significantly lower than the TCD50, of 68 (60; 81) after low initial doses (p=0.03). The TCD50 value of 62 Gy (57; 68) after constant doses was intermediate (constant vs increasing p =0.30; constant vs decreasing p=0.15). The higher efficacy of high initial doses in FaDu tumours was explained by local control occurring already during the course of irradiation. In GL tumours the TCD50 values were 52 Gy (43; 62) after high initial dose intensity, 50 Gy (43; 66) after constant doses, and 55 Gy (42; 89) after low initial dose intensity. These values were not statistically different (p-values 0.20-0.75). CONCLUSIONS: The data support the view that initial dose concentration during fractionated irradiation does not enhance radioresistance of FaDu and GL tumours, for instance by an earlier onset of clonogen repopulation.

Animals↗
PubMed2000

Fibrinogen levels and obstructive sleep apnea in ischemic stroke.

The plasma level of fibrinogen is felt to be an independent risk factor for vascular events. Obstructive sleep apnea (OSA) has a high prevalence in patients with stroke and may also be an independent risk factor. The aim of our study was to determine the association between OSA and plasma levels of fibrinogen in patients with stroke. Polysomnography was performed during neurological rehabilitation in 113 patients (82 men, 31 women, age 58 +/- 11.1 yr, mean +/- SD) with ischemic stroke. OSA was absent (RDI < 5) in 44 patients, 42 had mild OSA (5 < or = RDI < 20), and 27 had moderate to severe OSA (RDI > or = 20). Parameters of OSA (respiratory disturbance index [RDI], oxygen indices) were correlated to plasma levels of fibrinogen, measured in the morning after admission to rehabilitation. Fibrinogen was positively correlated with RDI (r = 0.24, p = 0.007), duration of the longest apnea (r = 0.18, p = 0.049), and negatively correlated with several oxygen indices including average minimal oxygen saturation (r = -0.41, p < 0.001). Correlation coefficients were slightly higher when excluding patients with stroke of presumed cardiac origin. Multiple linear regression identified minimal mean oxygen saturation and sex as independent predictors of fibrinogen level. The correlation between severity of coexisting OSA and fibrinogen level in patients with stroke suggests a possible pathophysiological mechanism for an increased risk of stroke in patients with OSA.

Aged↗
PubMed1999

Mutation induction by different types of radiation at the Hprt locus.

Mutation induction at the Hprt locus in Chinese hamster cells was studied after exposure to ultraviolet light, X-rays and alpha particles. While mutant frequency as a function of dose or fluence followed a linear-quadratic relationship with UV and X-rays, it showed a linear dependence for alpha particles. If mutant frequency is plotted vs. the logarithm of surviving fraction, a linear relationship is found in all cases although with different slopes. These are about equal with the two types of ionising radiations but about 10 times larger for UV. They can be used as a measure of mutagenic potential and are termed mutagenicity. It is shown that this parameter is correlated with the maximum of mutant yield, i.e., the number of mutants per cell at risk. It is concluded from this analysis that the maximum mutant yield is always found at doses or fluences which lead to 37% survival irrespective of the kind of radiation. If mutation induction is measured in X-irradiated cells after pre-exposure to UV, mutant frequency is higher than expected on the basis of independent action of the two radiations. Deletion spectra were determined by using multiplex polymerase chain reaction. It was found that the background of spontaneous mutants varied considerably and showed frequently repetitive patterns, presumably because of clonal expansion of pre-formed mutants. UV-induced mutants did not contain any deletions, while those with both X-rays and alpha particles the majority displayed partial and total deletions. Based on a total number of 134 X-ray- and 192 alpha-induced mutants, it is concluded that the total fraction of mutant clones without deletions (partial or total) is about 40% for X-rays and only about 20% for alpha-particles.

Alpha Particles↗
PubMed1999

The role of higher-order motor areas in voluntary movement as revealed by high-resolution EEG and fMRI.

In the human motor cortex structural and functional differences separate motor areas related to motor output from areas essentially involved in higher-order motor control. Little is known about the function of these higher-order motor areas during simple voluntary movement. We examined a simple finger flexion movement in six healthy subjects using a novel brain-imaging approach, integrating high-resolution EEG with the individual structural and functional MRI. Electrical source reconstruction was performed in respect to the individual brain morphology from MRI. Highly converging results from EEG and fMRI were obtained for both executive and higher-order motor areas. All subjects showed activation of the primary motor area (MI) and of the frontal medial wall motor areas. Two different types of medial wall activation were observed with both methods: Four of the subjects showed an anterior type of activation, and two of the subjects a posterior type of activation. In the former, activity started in the anterior cingulate motor area (CMA) and subsequently shifted its focus to the intermediate supplementary motor area (SMA). Approximately 120 ms before the movement started, the intermediate SMA showed a drop of source strength, and simultaneously MI showed an increase of source strength. In the posterior type, activation was restricted to the posterior SMA. Further, three of the subjects investigated showed activation in the inferior parietal lobe (IPL) starting during early movement preparation. In all subjects showing activation of higher-order motor areas (anterior CMA, intermediate SMA, IPL) these areas became active before the executive motor areas (MI and posterior SMA). We suggest that the early activation of the anterior CMA and the IPL may be related to attentional functions of these areas. Further, we argue that the intermediate part of the SMA triggers the actual motor act via the release of inhibition of the primary motor area. Our results demonstrate that a noninvasive, multimodal brain imaging technique can reveal individual cortical brain activity with high temporal and spatial resolution, independent of a priori physiological assumptions.

Adult↗
PubMed1998

A comparison between electric source localisation and fMRI during somatosensory stimulation.

The present study investigates the electric source localisation of somatosensory evoked potentials (SEPs) using high-resolution EEG (61 scalp electrodes) considering the individual brain morphology as obtained from magnetic resonance images (MRI). A comparison with the activation maps in fMRI under the same somatosensory stimulation paradigm was done. The somatosensory evoked potentials (SEPs) to electrical stimulation of the right median nerve were collected from the scalp of 8 healthy right-handed subjects. The source reconstruction for the 20 ms SEP component was performed by using a single moving dipole model as a source model and a spherical three-shell model as a head model. In 6 of the subjects fMRI was performed using the same electric stimulation of the right median nerve. The source location of the 20 ms SEP component was found to be within the postcentral gyrus. The fMRI activation maps were also located in the postcentral gyrus when using the same somatosensory stimulation paradigm. The appropriateness of using high-resolution EEG and fMRI in the functional localisation of the primary somatosensory cortex is discussed.

Adult↗
PubMed1998

Immunogenetic evidence for the phylogenetic sister group relationship of dogs and bears (Mammalia, Carnivora: Canidae and Crsidae). a comparative determinant analysis of carnivoran albumin, c3 complement and immunoglobulin micro-chain.

Thirty-seven antigenic determinants were identified in the albumins, the immunoglobulin micro- and IgG(Fc) chains, and the C3 proteins of 51 carnivoran (sub)species from 31 genera, and in 12 noncarnivoran mammals. In addition to 19 determinants plesiomorphic for Carnivora as an order, 18 synapomorphic epitopes of carnivoran families revealed nine phylogenetic reaction groups: (1) canids, (2) ursids, (3) the racoon, (4) the Weddell seal, (5) the lesser panda, (6) the harbour seal, (7) mustelids, (8) viverrids and hyaenas, and (9) felids. These data identify Canoidea (Canidae, Ursidae, Phocidae, Procyonidae, Ailuridae, Mustelidae) and Feloidea (Viverridae, Hyaenidae, Felidae) as two fundamentally differentiated lineages of Carnivora, and confirm the inclusion of seals among the former. The Ursidae are the sister group of the Canidae. The antigenic determinants in the studied proteins do not subdivide the Canidae, Ursidae and Felidae into immunologically differentiated lineages.

Albumins↗
PubMed1998

Recombinant human heart-type fatty acid-binding protein as standard in immunochemical assays.

Cytoplasmic heart-type fatty acid-binding protein has recently gained much attention in clinical diagnosis as a very early marker of acute myocardial infarction. Immunoassays have been developed for determination of this protein in plasma and urine samples. In the present study it is shown that those types of fatty acid-binding proteins which are abundant in tissues other than heart and muscle do not interfere with immunochemical determination of heart-type fatty acid-binding protein. To provide sufficient protein of consistent quality as standard in these immunoassays, human heart-type fatty acid-binding protein was cloned, expressed in Escherichia coli and purified to homogeneity. For quantitation of the recombinant protein its extinction coefficient was determined. Comparison of the recombinant and tissue-derived proteins by a variety of methods revealed both proteins to show similar kinetic as well as equilibrium constants with respect to two monoclonal antibodies currently applied in immunochemical detection of heart-type fatty acid-binding protein. Both preparations were indistiguishable in sandwich-ELISA and immunosensor measurements. A high stability of the recombinant protein was proven by ELISA measurements during storage and several freeze and thaw cycles. Thus, recombinant and tissue-derived heart-type fatty acid-binding proteins are immunochemically equivalent. The recombinant human heart-type fatty acid-binding protein is now available as standard for immunoassays.

Antibodies, Monoclonal↗
PubMed1997

Rho is required for the initiation of calcium signaling and phagocytosis by Fcgamma receptors in macrophages.

Phagocytosis of bacteria by macrophages and neutrophils is an essential component of host defense against infection. The mechanism whereby the interaction of opsonized particles with Fcgamma receptors triggers the engulfment of opsonized particles remains incompletely understood, although activation of tyrosine kinases has been recognized as an early step. Recent studies in other systems have demonstrated that tyrosine kinases can in turn signal the activation of small GTPases of the ras superfamily. We therefore investigated the possible role of Rho in Fc receptor-mediated phagocytosis. To this end we microinjected J774 macrophages with C3 exotoxin from Clostridium botulinum, which ADP-ribosylates and inactivates Rho. C3 exotoxin induced the retraction of filopodia, the disappearance of focal complexes, and a global decrease in the F-actin content of J774 cells. In addition, these cells exhibited increased spreading and the formation of vacuolar structures. Importantly, inactivation of Rho resulted in the complete abrogation of phagocytosis. Inhibition of Fcgamma receptor-mediated phagocytosis by C3 exotoxin was confirmed in COS cells, which become phagocytic upon transfection of the FcgammaRIIA receptor. Rho was found to be essential for the accumulation of phosphotyrosine and of F-actin around phagocytic cups and for Fcgamma receptor-mediated Ca2+ signaling. The clustering of receptors in response to opsonin, an essential step in Fcgamma-induced signaling, was the earliest event shown to be inhibited by C3 exotoxin. The effect of the toxin was specific, since clustering and internalization of transferrin receptors were unaffected by microinjection of C3. These data identify a role for small GTPases in Fcgamma receptor-mediated phagocytosis by leukocytes.

Actins↗
PubMed1997

Reproducibility and validity of electric source localisation with high-resolution electroencephalography.

The present study investigates the reproducibility and validity of the EEG source localisation of somatosensory evoked potentials (SEPs) using high-resolution EEG (61 scalp electrodes) and a source reconstruction on the basis of the individual brain morphology as obtained from magnetic resonance images (MRIs). The somatosensory evoked potentials (SEPs) to electrical stimulation of the right median nerve were repeatedly collected from the scalp of one healthy subject in 9 replications run on 9 different days. The source reconstruction for the 19 ms SEP component was performed by using a single moving dipole model as a source model. Two different head models were used: a spherical 3 shell model and a more realistically shaped 3 compartment model computed using the boundary element method (BEM). The source locations of the 19 ms SEP component were found to be highly reproducible using both head models: the mean standard deviation of the dipole locations was found to be 2.6 mm for the 3 shell model and 4 mm for the more realistically shaped head model. By projection into the individual MRI, the dipoles resulting from either head models were found to be located within the postcentral gyrus. The electric source locations were consistent with the maximum of the task-specific changes seen in a functional magnetic resonance imaging (fMRI) experiment when using the same somatosensory stimulation protocol.

Brain Mapping↗
PubMed1997

An immunosensor based on disposable electrodes for rapid estimation of fatty acid-binding protein, an early marker of myocardial infarction.

An immunosensor was developed that allows the rapid estimation of fatty acid-binding protein (FABP) in neat plasma samples. FABP is released into the blood following myocardial infarction and elevated levels are found already 3 h after onset of symptoms. The sensor is based on screen-printed graphite working and Ag/AgCl reference electrodes and an immunosandwich procedure for the quantification of FABP. The capture antibodies are bound to the electrode surface by adsorption and will trap FABP from the plasma sample. The sandwich is then completed by a second monoclonal antibody conjugated with alkaline phosphatase. The enzyme converts p-aminophenylphosphate to p-aminophenol, which is detected amperometrically at +350 mV. The high binding capacity and very short response time of the working electrode allow within 20 min the quantification of FABP in the measuring range 10-350 ng/ml, covering the pathological range of FABP release into the circulation. Measurements of plasma samples from a patient with acute myocardial infarction show an excellent correlation of the results obtained with the biosensor and those obtained with the respective reference ELISA. Owing to the long stability of the electrodes with immobilized capture antibody (> 3 months) a quick application without the need of labour-intensive electrode preparation is possible.

Biomarkers↗
PubMed1997

Allozyme polymorphisms and biochemical-genetic taxon markers in lampreys (Lampetra, Eudontomyzon, Petromyzon).

Variation at 23 putative enzyme-coding loci was scored in 424 lampreys, including 321 European brook lampreys (Lampetra planeri), 83 European river lampreys (L. fluviatilis), 11 Ukrainian brook lampreys (Eudontomyzon mariae), and nine sea lampreys (Petromyzon marinus). Twelve polymorphisms are described for Lampetra species (LDH*, SOD-2*, PNP*, AAT-1*, AK-1*, ES-2*, LGL*, MPI*, GPI-1*. GPI-2*, PGM*, IDHP-2*), and two each for E. mariae (GPI-1*, ME-2*) and P. marinus (MDH-1*, ME-2*). Diagnostic allozymes are presented for the discrimination of lamprey taxa, some of which are difficult to recognize from the morphology of ammocoetes larvae, the life stage usually encountered when collecting cyclostomes. The allelic markers described permit the clear allocation to a genus, except for the species L. fluviatilis and L. planeri, which are not differentiated by qualitative allozyme analysis.

Animals↗
PubMed1997

Lumbar percutaneous endoscopic interbody fusion.

Since 1982, percutaneous endoscopic control has been found to be a fundamental help for selective posterior subligamentary decompression in lumbar contained disc herniations. After the first clinical experience in 1986 with percutaneous intervertebral bone grafting, the need for sufficient percutaneous preparation of the adjacent vertebral plates and postoperative immobilization of the operated on segment became evident. So in 1988, the original eccentrically abrasive end plate cutter for application under discoscopy was introduced. For a preoperative trial and postoperative stabilization, the complementary use of the external pedicle fixation device was standardized in 1988. The use of percutaneous autologous bone interposition was found essential for optimal bony interbody consolidation. The indications were limited strictly to monosegmental lumbar dysfunctions without a need for peridural decompression. In a series of 37 patients with standardized procedure and a mean followup of 33 months, bony interbody consolidation was achieved in 30 cases. The technique desists from any need for blood transfusion, and functional rehabilitation is facilitated because of the very limited percutaneous approach.

Arthroscopy↗
PubMed1996

[Osteosarcoma and Ewing's sarcoma. Improved recovery chances in the past 25 years according to the experience of Balgrist Hospital].

At the Balgrist hospital 38 patients with osteosarcoma and 18 patients with Ewing sarcoma were treated from 1970 through 1992; a follow-up of at least three years is available for all patients. Disease-free survival in this period of time has increased from 20% (Ewing sarcoma) and 30% (osteosarcoma) to over 75%. While systemic tumor control was improved by systematic chemotherapy, local tumor control was improved by appropriate biopsy techniques, and amputations have been replaced by local resections, in most cases with reconstruction (arthrodesis, rotation plasty, endoprosthesis, allografts), which require further improvements. With respect to cure of the neoplastic disease, the currently available methods have been used to their maximum potential, and a steady state has been reached regarding survival. Further improvement of survival will therefore depend on the introduction of completely new modalities.

Adolescent↗
PubMed1996

NADH diaphorase polymorphism in European fallow deer.

NADH diaphorase polymorphism is reported for European fallow deer (D. d. dama) from Coto de Doñana National Park (Spain). Allele frequencies of p = 0.682 (anodic variant) and q = 0.318 (cathodic variant) in 110 specimens suggest population genetic usefulness of this biallelic system in an otherwise fairly monomorphic cervid species.

Animals↗