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Biomedical subjects

R Fischer

Publications and source records attributed to R Fischer.

At least 127 records · Page 7Linked to original sources
PubMed2000

Background estimation in experimental spectra

A general probabilistic technique for estimating background contributions to measured spectra is presented. A Bayesian model is used to capture the defining characteristics of the problem, namely, that the background is smoother than the signal. The signal is allowed to have positive and/or negative components. The background is represented in terms of a cubic spline basis. A variable degree of smoothness of the background is attained by allowing the number of knots and the knot positions to be adaptively chosen on the basis of the data. The fully Bayesian approach taken provides a natural way to handle knot adaptivity and allows uncertainties in the background to be estimated. Our technique is demonstrated on a particle induced x-ray emission spectrum from a geological sample and an Auger spectrum from iron, which contains signals with both positive and negative components.

Journal Article↗
PubMed2000

Release of osmolytes induced by phagocytosis and hormones in rat liver.

Betaine, taurine, and inositol participate as osmolytes in liver cell volume homeostasis and interfere with cell function. In this study we investigated whether osmolytes are also released from the intact liver independent of osmolarity changes. In the perfused rat liver, phagocytosis of carbon particles led to a four- to fivefold stimulation of taurine efflux into the effluent perfusate above basal release rates. This taurine release was inhibited by 70-80% by the anion exchange inhibitor DIDS or by pretreatment of the rats with gadolinium chloride. Administration of vasopressin, cAMP, extracellular ATP, and glucagon also increased release of betaine and/or taurine, whereas insulin, extracellular UTP, and adenosine were without effect. In isolated liver cells, it was shown that parenchymal cells and sinusoidal endothelial cells, but not Kupffer cells and hepatic stellate cells, release osmolytes upon hormone stimulation. This may be caused by a lack of hormone receptor expression in these cells, because single-cell fluorescence measurements revealed an increase of intracellular calcium concentration in response to vasopressin and glucagon in parenchymal cells and sinusoidal endothelial cells but not in Kupffer cells and hepatic stellate cells. The data show that Kupffer cells release osmolytes during phagocytosis via DIDS-sensitive anion channels. This mechanism may be used to compensate for the increase in cell volume induced by the ingestion of phagocytosable material. The physiological significance of hormone-induced osmolyte release remains to be evaluated.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2000

Factors influencing effectiveness of deferiprone in a thalassaemia major clinical setting.

The effectiveness of deferiprone (L1) and the influence of other factors were determined in a clinical setting. Patients of Southern Italian origin, affected by beta-thalassaemia major (n = 13: 7 M, 6 F), aged 10-28 years (median 18 years), were treated with L1 within a 'Controlled Programme' of the Italian Ministry of Health. Desferrioxamine could not be administered in these patients because of anaphylactic reactions or other serious side effects. L1 was considered to be effective when the liver iron concentration was reduced or stable as measured by biomagnetic liver susceptometry. L1 proved to be effective in 3 out the 9 evaluable patients. A high pre-L1 iron overload was the main clinical factor influencing L1 effectiveness.

Adolescent↗
PubMed2000

Theophylline improves acute mountain sickness.

A randomized two-part study was conducted in order to determine the efficacy of theophylline in the treatment of acute mountain sickness during fast ascent to altitudes >2,500 m. Fourteen healthy male subjects participated in a randomized single-blind placebo-controlled crossover study carried out in a decompression chamber (simulated altitude 4,500 m). A second randomized single-blind, placebo-controlled study was conducted at a high-altitude research laboratory (3,454 m) and included 21 healthy male subjects. The study medication was either 375 mg oral slow-release theophylline (250 mg if <70 kg) or a matched placebo tablet taken twice daily. The acute mountain sickness score (AMSS) was assessed three times a day, beginning 18 h prior to altitude exposure and continuing for 18 h after altitude exposure. In addition, measurements of respiratory frequency, pulse rate, oxygen saturation and arterial blood gas levels were performed. Acute mountain sickness was significantly reduced by theophylline during the decompression chamber study (mean+/-SD 1.2+/-0.9) with placebo versus 3.6+/-0.8 with theophylline; p=0.03). During the high-altitude study, subjects with theophylline showed a significantly lower AMSS on arrival and after 18 h at altitude (0.6 versus 2.3, p=0.03). Oxygenation was improved in both parts of the study. In conclusion, oral slow-release theophylline improves acute mountain sickness.

Administration, Oral↗
PubMed2000

Bone marrow features and clinical findings in chronic myeloid leukemia--a comparative, multicenter, immunohistological and morphometric study on 614 patients.

A multicenter, immunohistochemical and morphometric study was performed on diagnostic pretreatment bone marrow biopsies in 614 adult patients with Ph1+ chronic myeloid leukemia (CML) to compare histological features with clinical findings. For identification of megakaryopoiesis we used the monoclonal antibody CD61 and additionally the PAS reaction to determine the subfraction of atypical micromegakaryocytes and precursors. Labelling of erythroid precursors was carried out by a monoclonal antibody directed against glycophorin C. In order to selectively stain macrophages and their activated subset we applied CD68 and the GSA-I lectin. Density of argyrophilic fibers (reticulin plus collagen) was measured following Gomori's silver impregnation method. In accordance with laboratory data morphological variables revealed a comparable amount of congruence in the various groups of CML patients derived from different sources. In about 26% of patients early (reticulin) to advanced (collagen) fibrosis was detectable. Significant correlations were calculated between the extent of myelofibrosis with splenomegaly, anemia and increasing numbers of erythroblasts and myeloblasts in the peripheral blood count. These features were assumed to indicate more advanced stages of the disease process with ensuing transition into myeloid metaplasia and consequently were associated with an unfavorable prognosis. Significant relationships were revealed between the number of CD61+ megakaryocytes and more important, also their precursor fraction with the degree of fibrosis. This result extends previous experimental findings regarding the impact of immature elements of this cell lineage for the generation of myelofibrosis. The significant association of erythroid precursors with the number of mature (resident) macrophages including their activated GSA-I subset may shed some light on their functional involvement in iron turnover and hemoglobin synthesis. A modified histological classification of predominant bone marrow features is introduced. This simplified synthesis staging system (Cologne Classification) is not only associated with certain sets of laboratory data, but also with different survival patterns.

Adult↗
PubMed1999

Intratesticular leiomyosarcoma in a young man after high dose doping with Oral-Turinabol: a case report.

BACKGROUND: Androgenic anabolic steroids have been suspected of activity as carcinogens in the development of carcinoma and angiosarcoma of the liver and adenocarcinoma of the prostate. Although the proliferation of smooth muscle cells is stimulated by sexual steroids, to the authors' knowledge a possible relation between androgenic anabolic steroids and the development of leiomyosarcoma has not previously been reported in humans. METHODS: A 32-year-old man underwent right radical orchiectomy for a tumor of the upper pole of the right testicle. Routine histopathologic examination and immunohistochemical staining were performed. RESULTS: The tumor was identified as an intratesticular leiomyosarcoma based on its typical growth pattern and the characteristic immunohistochemical staining profile. The patient reported a 5-year history of systematic use of high dose Oral-Turinabol (4-chloro-1-dehydro-17alpha-methylteststerone) that began at age 18 years and stopped approximately 9 years before presentation. CONCLUSIONS: The rarity of intratesticular leiomyosarcoma, the experimental induction of similar tumors in animals by androgens and estrogens, and the unusually young age at presentation of the patient in the current study support the hypothesis that high dose doping with androgenic anabolic steroids could have played a cocarcinogenic role in the development of the tumor in this case.

Actins↗
PubMed1999

Transient expression of a tumor-specific single-chain fragment and a chimeric antibody in tobacco leaves.

To evaluate the expression of different forms of a tumor-specific antibody in plants, we adapted a recently described Agrobacterium-mediated transient expression system. A recombinant single-chain Fv antibody (scFvT84.66) and a full-size mouse/human chimeric antibody (cT84.66) derived from the parental murine mAb T84. 66 specific for the human carcinoembryonic antigen were engineered into a plant expression vector. Chimeric T84.66 heavy and light chain genes were constructed by exchanging the mouse light and heavy chain constant domain sequences with their human counterparts and cloned into two independent plant expression vectors. In vivo assembly of full-size cT84.66 was achieved by simultaneous expression of the light and heavy chains after vacuum infiltration of tobacco leaves with two populations of recombinant Agrobacterium. Upscaling the transient system permitted purification of functional recombinant antibodies from tobacco leaf extracts within a week. His6-tagged scFvT84.66 was purified by immobilized metal affinity chromatography and cT84.66 by protein A affinity chromatography. Sufficient amounts of recombinant antibodies were recovered for detailed characterization by SDS/PAGE, Western blotting, and ELISA.

Animals↗
PubMed1999

Affinity-purification of a TMV-specific recombinant full-size antibody from a transgenic tobacco suspension culture.

A TMV-specific full-size murine IgG-2b/K antibody (mAb24) was expressed in a Nicotiana tabacum cv. Petite Havana SR1 suspension culture (P9s), which was derived from a stably transformed transgenic plant (P9). The integration of an N-terminal murine leader peptide directed the assembled immunoglobulin for secretion. However, in suspension culture, the full-size recombinant antibody, rAb24, was retained by the plant cell wall and was not present in the culture medium. rAb24 expression reached a basal level of 15 microg per gram wet cell weight, corresponding to 0.3% of the total soluble plant cell protein. The level of rAb24 could be increased three-fold by amino acid supplementation of the culture medium. For purification of the recombinant antibody from batch-cultured tobacco suspension cells, the primary plant cell wall was partially digested by enzymatic treatment. This resulted in a total release of recombinant full-size rAb24 into the extraction buffer. A three-step procedure was used to purify the immunoglobulins, starting with cross-flow filtration (step 1) followed by protein A affinity chromatography (step 2) and gel filtration as a final purification step (step 3). This procedure gave a recovery of more than 80% of the expressed rAb24 from plant cell extracts. SDS-PAGE, IEF and immunoblot analyses demonstrated a high degree of homogeneity for the affinity-purified rAb24. An ELISA procedure demonstrated that the specificity and affinity of the protein A affinity purified antibody was indistinguishable from its murine counterpart, indicating the potential of plant cell suspension cultures as bio-reactors for the production of recombinant antibodies.

Animals↗
PubMed1999

Immunological analysis of potato leafroll luteovirus (PLRV) P1 expression identifies a 25 kDa RNA-binding protein derived via P1 processing.

Mono- and polyclonal antibodies directed against different domains of the potato leafroll luteovirus (PLRV) P1 (ORF1) protein were applied to the analysis of P1 expression during PLRV replication in planta. Western analyses detected P1 and a protein of approximately 25 kDa (P1-C25) that accumulated to readily detectable amounts in PLRV-infected plants, but was not detected by in vitro cell-free translation of P1. P1-C25 represents the C-terminus of P1 and is a proteolytic cleavage product produced during P1 processing. On the basis of its molecular weight, the N-terminus of P1-C25 is either identical to or located adjacent to the previously identified PLRV genome-linked protein, VPg. P1-C25 is not associated with virus particles, and subcellular localization experiments detected P1-C25, but not P1, in the membrane and cytoplasmic fractions of PLRV-infected cells. In addition, P1-C25 exhibits nucleic acid-binding properties. On the basis of its biosynthesis, localization and biochemical properties, P1-C25 may facilitate the formation of P1/PLRV RNA complexes in which the spatial proximity allows for covalent bond formation between PLRV RNA and VPg.

Antibodies, Monoclonal↗
PubMed1999

Assessment of iron stores in children with transfusion siderosis by biomagnetic liver susceptometry.

To investigate the applicability of noninvasive Superconducting Quantum Interference Device (SQUID) biomagnetic liver susceptometry and its limitations in thalassemic children, 23 patients with beta-thalassemia major and other iron loading anemias (age: 4-16 years) and 16 age-related normal children were studied. Liver iron concentrations ranged from 600 to 11,000 microg/g(liver) for thalassemic patients and from 60 to 340 microg/g(liver) for normal patients. Measuring the respective organ volumes by sonography, liver and spleen iron stores, accounting for 80% of total body iron stores, were estimated. Nonliver contributions from the lung or intestine to the measured SQUID signals in the small-sized patients were not observed. Moreover, livers in thalassemia were found to be enlarged by 18% per 1,000 microg/g (r = 0.75, P < 10(-3)). Serum ferritin values correlate significantly with iron stores (r = 0.64, P < 10(-3)), but predict iron stores only within large error intervals of 4,000 microg/g(liver). Analyzing the experimental data from biomagnetometry and from related transfusion and chelation treatment data within the framework of a two-compartment model, we were able to derive additional information on total body iron elimination and chelation therapy efficacy. The exponential decline of iron stores allows forecast of steady-state conditions of the final iron load for a particular transfusion and chelation therapy regimen.

Adolescent↗
PubMed1999

[Computer-based organization and documentation in orthopedics. A 5-year experience].

In the orthopedic department of the University Hospital Homburg/Saar, we use since 1993 a computer-based system for clinics organisation and documentation of operations. Hardware consists of DOS/Windows PC's in a Novell-network. Our software is a combination of database-system for managing patient-data and a special coding program for ICD and IKPM-digits. Our experience shows that computer assisted clinic-management is an effective tool to help the surgeon in planning and documentation. Until now, we used the system for 31,500 patients and 8500 operations. A flexible software can meet the requirements both of the surgeons and administration. Moreover, in the University hospital Homburg/Saar, the different departments are linked by an Intranet with connection to other scientific networks and the Internet.

Documentation↗
PubMed1999

Prognostic impact of apoptosis and proliferation in idiopathic (primary) myelofibrosis.

A retrospective study of 120 patients with the clinically and histologically established diagnosis of idiopathic (primary) myelofibrosis (IMF) was performed to determine prognostic factors of predictive value, including parameters characterizing the dynamics of hematopoietic cell kinetics. In contrast to previous studies, our cohort comprised the full spectrum of the disease, from initial prefibrotic to advanced osteosclerotic stages. The in situ end-labeling (ISEL) technique was used to demonstrate apoptosis, in order to determine dynamic parameters of predictive value. Cell proliferation was evaluated by employing the monoclonal antibody PC10 directed against proliferating cell nuclear antigen (PCNA). Proliferative activity (PCNA index) and frequency of apoptosis showed significant differences between early and advanced fibrosclerotic stages of disease. Decrease in proliferation indicated a significantly shorter survival, whereas a higher frequency of apoptotic cells was associated with a better prognosis. It may be speculated that a normal or enhanced proliferation rate expressed by PCNA positivity (late G1- and S-phase of the cell cycle) that is accompanied by a higher incidence of apoptosis reflects the regenerative (turnover) capacity of hematopoiesis. This may apply especially to early hypercellular stages without relevant myelofibrosis. In consideration of a recently published multivariate risk model, a simplified synthesis score for stratification of a patient's prognosis was constructed. Age, degree of anemia, leukocytes, and platelet count were regarded as the most important parameters. A substantial improvement of prognostic efficiency was further achieved by including PCNA index and frequency of apoptosis. Our results are in keeping with the assumption that generalization, indicated by myeloid metaplasia, has a prodigious impact on prognosis in IMF. Furthermore, in this context dynamic features such as proliferative activity and frequency of apoptosis exert an additional predictive value.

Age Factors↗
PubMed1999

Histochemistry and morphometry on bone marrow biopsies in chronic myeloproliferative disorders - aids to diagnosis and classification.

The aim of this review is to evaluate morphological characteristics of the different subtypes of chronic myeloproliferative disorders (MPDs) derived by applying immunohistochemical and morphometric techniques to bone marrow biopsies and to combine these results with relevant clinical parameters. In comparison to control specimens, a significant decrease in erythroid precursors is determinable in chronic myeloid leukemia (CML), while this cell lineage is most prominent in polycythemia vera (PV) and moderately to markedly reduced in idiopathic myelofibrosis (IMF). On the other hand, neutrophilic granulopoiesis shows a predominance in CML and a relevant increase in PV, but no conspicuous changes are detectable in essential thrombocythemia (ET). CML is characterized by a prevalent growth of dwarflike micromegakaryocytes, occurring in particular in the so-called megakaryocyte-rich subtypes (about 30%). This finding differs significantly from the pleomorphous aspect, i.e. , clusters of small to giant-sized megakaryocytes in PV and the grossly abnormal (dysplastic) appearance of this cell lineage in patients with IMF. Similar cytological abnormalities of megakaryopoiesis consistent with maturation defects are never encountered in ET. The incidence of mature (resident) macrophages (phagocytic reticular cells) is significantly enhanced in IMF in comparison to the other MPDs and controls. Moreover, there is a striking difference in the density of reticulin-collagen fibers, ranging from normal (ET) to extreme values (IMF). In IMF more than 80% of the patients present with some degree of myelofibrosis-osteosclerosis at diagnosis, while the rest show an initial prefibrotic, hypercellular stage. This feature deserves special attention since, when accompanied by thrombocythemia, it may simulate ET. Sequential bone marrow biopsies in patients with IMF disclose that evolution of myelofibrosis is progressive, but occurs at a variable and unpredictable speed. A synoptical approach regarding clinical diagnosis and histological subtyping of MPDs is explicitly recommended and demonstrated by sets of diagnostic criteria. This rationale requires equal consideration of laboratory data and morphology by clinicians to include well-defined subtypes of MPDs into prospective management studies. Furthermore, it may even warrant follow-up studies and repeated bone marrow examinations in initially unclassifiable cases.

Bone Marrow↗
PubMed1999

[Pneumococcal septicemia in functional asplenia: first manifestation of systemic autoimmune disease?].

A 35 year old female was admitted into the hospital because of rapid onset fever and chills. Streptococcus pneumoniae could be isolated from blood as the responsible pathogen for septicemia. Necroses of fingers and feet occurred. The clinical signs of an overwhelming post-splenectomy infection (OPSI) were evident. High-dose penicillin was administered and the patient recovered. Howell-Jolly-bodies were seen in peripheral blood smears. A spleen within normal size could be demonstrated in CT and sonography. Angiologic findings showed intact splenic arteries and a normal vein, whereas the small splenic vessels were rare. MRT of the spleen using Endorem (Fe), showed only a minimal uptake of the RES. In a scintigram of spleen and liver using 320 MBq Tc-99m nanokoll, the spleen was not visible. Thus, functional asplenia was demonstrated by Howell-Jolly-Bodies and by image methods. An increased antinuclear antibody level and a Sm-antibody lead to the diagnosis of undifferentiated connective tissue disease. As far as we know this is the first case that functional asplenia was the first symptom of a systemic autoimmune disease.

Adult↗
PubMed1999

Molecular characterization of HymA, an evolutionarily highly conserved and highly expressed protein of Aspergillus nidulans.

Aspergillus nidulans reproduces asexually via uninucleate, haploid spores, which are produced on morphologically differentiated aerial structures, called conidiophores. These consist of four distinct cell types, a foot with a terminally swollen stalk, metulae, phialides and conidiospores. The molecular mechanisms underlying the morphological changes that occur during conidiophore development have been studied by mutant analysis. We have isolated the hym A mutant, in which conidiophore development is affected at the metula stage. In the mutant metulae do not differentiate properly but come to resemble hyphae (hym = hypha-like metulae). In this paper we have analyzed the corresponding gene. It encodes a highly expressed 44 kDa protein which resides in the cytoplasm and has homologues in yeast, plants, fly, worm, fish, mice and man. We constructed hym deletion strains of Saccharomyces cerevisiae and of A. nidulans and found that the gene is essential in S. cerevisiae but is dispensable in the filamentous fungus. A cellular function for the Hym protein has not yet been defined in any organism. To demonstrate functional conservation we constructed a chimeric protein comprised of the N-terminal half of the A. nidulans and the C-terminal half of the mouse homologue MO25. This hybrid protein could fully substitute for HymA function in A. nidulans. In addition, the mouse protein itself partially rescued the hym A mutation in the fungus. HymA is thus highly conserved in evolution and probably serves similar functions. The fact that hym A is required for conidiophore development in A. nidulans suggests that homologous genes in other organisms might also be involved in morphogenesis.

Amino Acid Sequence↗