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Biomedical subjects

R Fischer

Publications and source records attributed to R Fischer.

At least 235 records · Page 13Linked to original sources
PubMed1996

Calmodulin binds to and inhibits GTP binding of the ras-like GTPase Kir/Gem.

Recently, a new subfamily of Ras-related GTP-binding proteins consisting of Rad (Ras associated with diabetes), Gem (immediate early gene expressed in mitogen-stimulated T-cells), and Kir (tyrosine kinase-inducible Ras-like) was discovered. The C terminus of these proteins contains an extension of approximately 30 amino acids not present in other members of the Ras family and which exhibits all the hallmarks typical for calmodulin (CaM)-binding domains. A peptide corresponding to the putative CaM-binding domain of the Kir/Gem protein was synthesized, and its affinity for CaM was determined by fluorescence spectrometry. Titration of dansyl-CaM with the Kir/Gem peptide gave an affinity constant of 1 nM. Furthermore, a single point mutation of the peptide, W269G, abolished this high affinity interaction. Gel-shift analysis showed that the complex formation between CaM and the Kir/Gem peptide is strictly calcium-dependent. We also demonstrate with a newly developed [32P]CaM overlay technique that full-length Kir/Gem and Rad proteins bind CaM in a Ca2+-dependent fashion. The binding of CaM to glutathione S-transferase-Kir and GST-Gem inhibited the binding of GTP to Kir/Gem significantly. These results suggest the existence of a direct link between Ca2+/CaM and growth factor signal transduction pathways at the level of small Ras-like GTPases.

Amino Acid Sequence↗
PubMed1996

Binding of contactin/F11 to the fibronectin type III domains 5 and 6 of tenascin is inhibited by heparin.

The structural basis for the interaction between tenascin-C and the neuronal cell adhesion molecule, contactin/F11, was investigated using plasmon surface resonance technology. The binding site on tenascin-C for contactin/F11 is shown to span the two fibronectin type III homology domains 5 and 6. Either domain alone is insufficient for binding. Heparin, heparan sulfate and dermatan sulfate inhibit this interaction through binding to a conserved heparin-binding site on domain 5. In contrast, chondroitin sulfates A and C have no such effect.

Animals↗
PubMed1996

Identification of a Hydra homologue of the beta-catenin/plakoglobin/armadillo gene family.

The beta-catenin/plakoglobin/armadillo gene family encodes a group of highly conserved proteins which play important roles in cadherin-mediated cell adhesion and in signal transduction mechanisms involved in regulating development. This gene family previously had been isolated only from higher metazoans. Here, we describe the isolation and characterization of a beta-catenin (beta Ctn) homologue from Hydra magnipapillata, a diploblastic lower metazoan. Comparison of the putative amino acid (aa) sequence of Hydra beta Ctn, with its homologues in higher metazoans, shows that a repeating 42-aa motif present in its central domain is highly conserved throughout the metazoa. This suggests that beta Ctn appeared very early in metazoan evolution, possibly when primitive multicellular animals started to form epithelial cell layers.

Amino Acid Sequence↗
PubMed1996

Platelet-activating factor is involved in the regulation of pathological leukocyte adhesion after liver transplantation.

An increased leukocyte adhesion and loss of integrity of endothelial cells is known to be a critical step in the reperfusion period after cold ischemia of transplanted livers. Platelet-activating factor (PAF) is discussed as one of the inflammatory mediators involved in mediating reperfusion injury, e.g., by regulation of leukocyte adhesion. In this study we investigated the effect of a synthetic PAF receptor antagonist, WEB 2086 (Boehringer Ingelheim, FRG), on microcirculation and adhesion of leukocytes to sinusoidal endothelium after liver transplantation in the rat. Livers from SPRD rats (n = 6 per group) were stored for 5 hr in ice-cold UW solution and orthotopically transplanted using the cuff technique. In a randomized and blinded fashion WEB 2086 (1 mg/kg body wt) or placebo was given twice intravenously, at the beginning of the recipient operation and 1 min prior to reperfusion of the liver graft. After in vivo staining of leukocytes with acridine orange, microcirculation and leukocyte-endothelium interaction of transplanted livers and livers from sham-operated animals were investigated 90 min and 5 hr after surgery by means of intravital microscopy. After 90 min of reperfusion, temporary leukocyte adhesion in periportal regions was increased after liver transplantation (22.0 +/- 2.5%; mean +/- SEM) in contrast to the sham group (14.2 +/- 1.8%). Administration of WEB 2086 reduced temporary leukocyte adhesion significantly (11.5 +/- 2.5%; P < 0.05), whereas no significant differences were observed with respect to permanent leukocyte adhesion. Five hours after recipient operation, a significant increase of permanent leukocyte adhesion was observed after transplantation (21.0 +/- 2.6%; P < 0.05) compared to sham-operated animals (12.1 +/- 1.7%). Application of WEB 2086 diminished permanent leukocyte adhesion significantly (12.2 +/- 1.3%; P < 0.05), whereas no differences were noticed between the different groups with respect to temporary leukocyte adhesion at this time. The results indicate that reduction of temporary leukocyte adhesion in the early reperfusion period by administration of PAF receptor antagonist WEB 2086 was followed by a reduction of permanent leukocyte adhesion in the late reperfusion period, e.g., at 5 hr. Thus, it is concluded that PAF is one of the mediators which is involved in the regulation of leukocyte adhesion after liver transplantation.

Animals↗
PubMed1996

Effects of continuous-wave laser systems on stapes footplate.

BACKGROUND AND OBJECTIVE: The aim of the present study was to clarify which of the presently available continuous-wave laser systems are best suited for application in stapes surgery. STUDY DESIGN/MATERIALS AND METHODS: Isolated human stapes and bovine compact-bone platelets were used to investigate the connections between the parameters of various laser systems and their effects on bone tissue. The purpose was to optimize the laser parameters required to achieve a perforation measuring 500 microns to 600 microns in diameter. Three different laser systems were applied: the argon and CO2 laser in continuous wave (cw) mode and the CO2 laser in superpulse mode. RESULTS: The suitability of the argon laser for stapedotomy is doubtful in view of the lower absorption coefficient of the stapes for the argon beam and the considerable influence which the degree of pigmentation of the irradiated medium exerts on its effect with the resultant poor reproducibility of the perforation diameter. The beam of the CO2 laser is far better absorbed at the footplate than that of the argon laser. This results in higher effectivity, lower thermic side effects, and better reproducibility of the perforation. The two modes of the CO2 laser do not show any appreciable differences. CONCLUSION: The experimental results presented indicate that the CO2 laser in cw and superpulse mode is the most suitable of the systems now clinically applied in stapes surgery.

Animals↗
PubMed1996

[Blood group antigen expression in papillary carcinoma of the thyroid gland. An immunohistochemical and clinical study of expression of Lewis, ABO and related antigens].

Nine monoclonal antibodies, lectin from Ulex europaeus and neuraminidase enzyme were employed to demonstrate the occurrence of type 1 and type 2 blood group antigens in 104 cases of papillary carcinoma of the thyroid. The reagents applied, recognize the following blood group related antigens: CA-50 (sialylated type 1 precursor), CA-19-9 (sialylated Le(a)), Le(a), Le(b), A, B, H, Le(x), sialylated Le(x), and Le(y). Immunohistochemical studies revealed that papillary carcinoma of the thyroid, in contrast to histologically normal thyroid tissue, is characterised by a progressive expression of blood group antigens. Most tumours (84%) reacted with C-50 antibody, whereas only a minority of the tissues demonstrated the CA-19-9 antigen (38%). Type 2 structures Le(x) (47%) and Le(y) (13%) were found less often than their corresponding type 1 isomers Le(a) (71%) and Le(b) (62%). Desialylation with neuraminidase increased the Le(a) and Le(x) staining intensity in 27 and 44 case, respectively. Of the A, B, H antigens the A determinants encountered most frequently (24%). Comparative examinations of sequential sections of the same tumour revealed coexpression of type 1 antigens in the same areas. In carcinomas showing type 1 and type 2 antigen reactivity, a complementary distribution of the structures in different tumour areas was often demonstrated. Some tumours presented combined type 1 and type 2 antigen expression in the same cells, however, in distinct areas within the cell. A follow-up examination was carried out in 68 of the 104 cases. The observation time ranged from 12 to 217 months. Thirteen patients suffered from recurrence, of which 7 died. While lymphatic metastases occurred in 39 tumours, distant metastases were detected in 6 patients. Most of the recurrences were found in patients with tumour classification pT4 (n = 19), whereas none of the pT1 carcinomas (n = 20) showed recurrence. The clinical results were compared to the blood group antigen expression results. There was no correlation between antigen expression and differentiation degree of the tumour. The pT4 tumours showed a significant higher expression of the CA-50, CA-19-9, Le(a) and Sialyl Le(x) structures. Carcinomas expressing the Le(y) antigen were associated with a significant higher level of metastasizing capacity. The Le(y), H type 1 and H type 2 antigens occurred more frequently in recurrent tumours (n = 14). In contrast, none of the patients whose carcinomas expressed the A-antigens (n = 14) suffered from a recurrence or hematogenous metastasis. Multiple stepwise regression analysis was carried out to check the importance of each staining and clinical factor. In this analysis, "distant metastasis' was the most important parameter, whereas the staining results were of minor statistical importance.

ABO Blood-Group System↗
PubMed1996

Characterization of the binding specificity of Anguilla anguilla agglutinin (AAA) in comparison to Ulex europaeus agglutinin I (UEA-I).

Using immunochemical and immunohistochemical methods, the binding site of Anguilla anguilla agglutinin (AAA) was characterized and compared with the related fucose-specific lectin from Ulex europaeus (UEA-I). In solid-phase enzyme-linked immunoassays, the two lectins recognized Fuc alpha 1-2Gal beta-HSA. AAA additionally cross-reacted with neoglycolipids bearing lacto-N-fucopentaose (LNFP) I [H type 1] and II [Le(a)] and lactodifucotetraose (LDFT) as glycan moieties. UEA-I, on the other hand, bound to a LDFT-derived neoglycolipid but not to the other neoglycolipids tested. Binding of AAA to gastric mucin was competitively neutralized by Le(a)-specific monoclonal antibodies. UEA-I binding, on the other hand, was reduced after co-incubation with H type 2- and Le(y)-specific monoclonal antibodies. According to our results, AAA reacts with fucosylated type 1 chain antigens, whereas UEA-I binds only to the alpha 1-2-fucosylated LDFT-derived neoglycolipid. In immunohistochemical studies, the reactivity of AAA and UEA-I in normal pyloric mucosa from individuals with known Lewis and secretor status was analysed. AAA showed a broad reaction in the superficial pyloric mucosa from secretors and non-secretors, but AAA reactivity was more pronounced in Le(a+b-) individuals. On the other hand, UEA-I stained the superficial pyloric mucosa only from secretor individuals. A staining of deep mucous glands by the lectins was found in all specimens. Both reacted with most human carcinomas of different origin. Slight differences in their binding pattern were observed and may be explained by the different fine-specificities of the lectins.

Agglutinins↗
PubMed1996

Tumor localization of anti-CEA single-chain Fvs: improved targeting by non-covalent dimers.

BACKGROUND: Genetic engineering can produce novel antibody fragments with improved properties for applications such as tumor targeting in vivo. OBJECTIVES: To produce stable monomeric (27 kDa) and dimeric (55 kDa) forms of a single-chain Fv (scFv) from the anti-carcinoembryonic antigen (anti-CEA) antibody T84.66, and assess the targeting and biodistribution properties in an animal model. STUDY DESIGN: ScFv were constructed with either a 28 or 14 amino acid connecting peptide and expressed by secretion from E. coli. Following affinity purification, proteins were characterized by gel electrophoresis and mass spectrometry. Binding properties were assessed by size exclusion HPLC after incubation with antigen, and affinities determined by surface plasmon resonance. The shorter linker favored formation of dimers (and higher multimers) which showed unusual stability. ScFv were radiolabeled with 125I for tumor targeting and biodistribution studies of monomeric or dimeric forms were conducted in athymic mice bearing LS174T human colorectal carcinoma xenografts. RESULTS: 125I-scFv monomers and dimers targeted exhibited rapid clearance kinetics in tumor-bearing mice. Nevertheless, the anti-CEA scFvs targeted very well to xenografts, leading to high tumor: normal organ ratios (greater than 20:1 at 24 h) for both forms. Tumor localization of the non-covalent dimers was much higher than monomers, reaching 10-15% injected dose per gram at 1 h. CONCLUSION: Non-covalent dimers of scFv (also known as diabodies) are stable, easy to produce and show excellent targeting as compared to monomeric scFv, probably due to increased mass and valency.

Animals↗
PubMed1996

Atypical lymphoid infiltrations of the gastric mucosa--their interpretation and management by eradication of Helicobacter pylori.

Low-grade gastric lymphomas of mucosa-associated lymphoid tissue (MALT) may be extremely difficult to differentiate from atypical lymphoid infiltrations of the gastric mucosa caused by Helicobacter pylori (H. pylori) infection, especially if lympho-epithelial destructions are not detected. In order to clarify this diagnostic problem and to evaluate the potential benefit of clearing H. pylori-induced lymphoid infiltration a prospective study was performed. Our study included biopsy specimens from 61 patients, that showed excessive lymphoid infiltrations. Using histology and immunohistochemistry no definite diagnosis could be delivered. In 46 (76.4%) cases histological regression occurred 4 weeks after the end of therapy suggesting a reactive infiltrate. In 7 patients (11.5%) the histological picture remained unchanged, and in 8 (13.1%) the follow-up biopsies revealed lympho-epithelial destructions allowing the diagnosis of low-grade MALT lymphoma. On the basis of our data we conclude that eradication of H. pylori could provide an additional tool in the differential diagnosis between atypical lymphoid infiltrations of the gastric mucosa caused by H. pylori and an early primary gastric MALT lymphoma.

Adult↗
PubMed1996

Distribution of von Willebrand factor in capillary endothelial cells of rat lungs with pulmonary fibrosis.

To determine the value of von Willebrand factor (vWF) antigen as a marker of endothelial injury in radiation-induced fibrosis of rat lungs, we studied endothelial immunoreactivity to antibodies against vWF using the indirect immunoperoxidase technique combined with morphometric analysis. Using immunoelectron microscopy of LR White embedded lung samples to detect vWF, immunogold-labelled Weibel Palade bodies were found in endothelial cells of capillary endothelium. The irradiated lungs showed a statistically significant elevation of vWF expression, ie, vWF positive endothelia per unit area, and a significant increase of vWF expression per unit of parenchyma as well. The results suggest that vWF antigen expression and the number of vWF positive structures is modulated under condition of injury in radiation-induced fibrosis.

Animals↗
PubMed1996

Recovery of memory and executive function following anterior communicating artery aneurysm rupture.

We studied the recovery of memory and executive function in 10 patients following anterior communicating artery aneurysm (ACoA) rupture and repair. Patients were tested at 2 consecutive points in time following surgery (approximately at 2 and 3 months). At the first testing, the patients divided into 2 groups based on the severity of impairment on executive measures. Both groups had severe anterograde amnesia, but only patients with severe executive impairments had retrograde amnesia with a temporal gradient. At second testing, both groups had persistent severe anterograde amnesia. The dysexecutive group showed significant improvement in executive deficits and in retrograde amnesia, with attenuation of the temporal gradient. Patients with more severe executive impairments had more extensive bilateral frontal lesions than other patients. These results suggest that the cognitive profile following ACoA rupture changes with time. Time postonset following aneurysm rupture and lesion site are both critical for defining the neuropsychological profile, and determining the underlying cognitive mechanisms in this neurological disorder.

Adult↗
PubMed1996

Long-term survival in patients with hereditary hemochromatosis.

BACKGROUND & AIMS: The course of hereditary hemochromatosis may depend on the degree of iron overload and the time of therapeutic intervention. This analysis evaluates the impact of early diagnosis and iron removal on survival and complications in hereditary hemochromatosis. METHODS: A Cohort of 251 patients with hemochromatosis was followed up for 14.1 +/- 6.8 years. RESULTS: Survival was reduced in the total group of patients when compared with a matched normal population. Survival in noncirrhotic and nondiabetic patients and in patients diagnosed between 1982 and 1991 was identical with rates expected. Survival was reduced in patients with severe iron overload vs. those with less severe overload. The percentage of early diagnoses increased threefold between 1947 and 1969 to that between 1970 and 1981; there was only a further 20%-25% increase in the last decade. Deaths caused by liver cancer, cardiomyopathy, liver cirrhosis, and diabetes mellitus were increased as compared with expected rates. Liver cancers were associated with cirrhosis and amount of mobilizable iron but not with hepatitis B or C markers. CONCLUSIONS: Prognosis of hemochromatosis and most of its complications, including liver cancer, depend on the amount and duration of iron excess. Early diagnosis and therapy largely prevent the adverse consequences of iron overload.

Adolescent↗
PubMed1996

Iron deficiency in distance runners. A reinvestigation using Fe-labelling and non-invasive liver iron quantification.

In a group of male distance runners, 23 out of 45 athletes showed decreased serum ferritin values (< 35 micrograms). The high prevalence of a typical iron deficiency in runners was confirmed in a subgroup of eight athletes in which the iron metabolism was studied in detail using radio-iron labelling and liver iron quantification. Most of these athletes showed an up-regulated 59Fe absorption and a decreased liver iron concentration as compared to a control group. 59Fe activity in collected samples of stool, urine or sweat was measured sensitively using a shielded high-pure germanium spectrometer. In periods without running, a faecal excretion of 59Fe equivalent to 1.5 ml blood loss/d was observed, which represents the normal iron excretion. Under intensive training or racing conditions, a significant increase up to 4.9-6.6 ml blood loss/day was observed, whereas excretion of 59Fe in urine or sweat was negligible. Thus, gastrointestinal blood loss was the main reason for the slightly negative iron balance in the runners. This confirms earlier studies in the literature using qualitative blood stool testing. A treatment with 100 mg ferrous iron/day for 3 months significantly increased the values for serum ferritin (from 34 +/- 11 to 54 +/- 18 micrograms/l) and liver iron (from 105 +/- 42 to 227 +/- 67 micrograms/g liver).

Adult↗
PubMed1996

The effect of lactulose on DNA damage induced by DMH in the colon of human flora-associated rats.

Germ-free rats were fed purified diets containing sucrose (0.3%, wt/wt) as control or the synthetic disaccharide lactulose (0.3% wt/wt) and were then dosed orally with a human fecal suspension. After five weeks on the diets, these "human flora-associated" rats were transferred to diets in which the sucrose or lactulose level was raised to 3% (wt/wt). Four weeks later, the rats from each dietary group were dosed orally with saline (controls) or 1,2-dimethylhydrazine dihydrochloride (DMH, 15 mg/kg). Sixteen hours after the carcinogen dose, the rats were killed, colon cells were isolated, and the degree of DNA damage in the cells was assessed using the single cell microgel electrophoresis (Comet) assay. Samples of cecal contents were also removed from the saline-treated rats to determine changes in composition of the gut microflora. No significant diet-related differences in cecal bacterial numbers were observed, although there was a trend for the numbers of lactobacilli to be higher in the lactulose-fed animals. DNA damage in colon cells was quantified by measurement of the length of the cellular DNA image after electrophoresis, and the evaluated cells were assigned to classes according to the degree of damage: undamaged (< 40 microns), moderately damaged (40-80 microns), or severely damaged (> 80 microns). There were no significant diet-related differences in DNA damage in colon cells from rats treated with saline. Treatment with DMH induced a highly significant increase in DNA damage in sucrose- and lactulose-fed rats. However, in the rats treated with DMH, the degree of DNA damage was significantly (p < 0.05) less in the lactulose-fed animals than in those given the sucrose diet, as evidenced by a decrease in the percentage of cells with severe damage. In the sucrose-fed rats, severely damaged cells accounted for 33% of the total compared with only 12.6% in the lactulose-fed DMH-treated animals. The results of this study, which was performed in human flora-associated rats to provide data of relevance to humans, indicate that lactulose consumption offered a degree of protection from the genotoxic effects in the colonic mucosa of a known colon carcinogen.

1,2-Dimethylhydrazine↗
PubMed1996

Effect of interferon therapy on bone marrow morphology in chronic myeloid leukemia: a cytochemical and immunohistochemical study of trephine biopsies.

The effect of interferon (IFN) therapy on bone marrow features in chronic myeloid leukemia (CML) has been studied on successive trephine biopsies (mean interval 13 +/- 8 months) by cytochemical and immunohistochemical methods in combination with morphometry and in comparison with a control group of patients who received monotherapy by busulfan (BU). Following IFN administration (IFN-alpha frequently in combination with IFN-gamma), there was a decrease in neutrophil granulopoiesis accompanied by a significant expansion of erythroid precursors and increased numbers of hemosiderin-laden macrophages. These changes corresponded with the hematologic response in 21 of the 25 patients investigated. Numbers of megakaryocytes and reticulin/collagen fiber density increased during treatment. Most conspicuously, in responding patients atypical micromegakaryocytes, usually characterizing CML, were partially replaced by normal-sized cells of this lineage. These features are in keeping with the assumption of a reappearance of the normal hematopoietic cell clone as the result of IFN therapy, which was not found in the BU-treated control group. On the other hand, a relevant subpopulation of micromegakaryocytes (about 30%) was still maintained. This result probably relates to the failure to improve myelofibrosis more effectively. Analysis of cell proliferation (proliferating cell nuclear antigen-PCNA) and apoptosis (in situ end labeling) revealed a reduction in PCNA labeling and increased numbers of cells undergoing programmed death. Identification of the activated subset of macrophages (alpha-D-galactosyl residues expression) by appropriate lectin histochemistry disclosed an increase in the number of GSA-I binding cells. These findings were exclusively limited to IFN administration and reflect an inhibitory effect of IFN on cell proliferation and stimulation of programmed cell death. The latter phenomenon probably results in increased phagocytosis of clonally transformed myeloid cells by GSA-I-positive (activated) macrophages.

Adult↗
PubMed1996

Isolation of two apsA suppressor strains in Aspergillus nidulans.

Aspergillus nidulans reproduces asexually with single nucleated conidia. In apsA (anucleate primary sterigmata) strains, nuclear positioning is affected and conidiation is greatly reduced. To get further insights into the cellular functions of apsA, aconidial apsA strains were mutagenized and conidiating suppressor strains were isolated. The suppressors fell into two complementation groups, samA and samB (suppressor of anucleate metulae), samA mapped on linkage group 1 close to pyrG. The mutant allele was dominant in diploids homozygous for apsA. Viability of conidia of samA suppressor strains (samA-; apsA-) was reduced to 50% in comparison to wild-type conidia. Eighty percent of viable spores produced small size colonies that were temperature and benomyl-sensitive. samB mapped to chromosome VIII and was recessive. Viability of conidia from samB suppressor strains (apsA-; samB) was also affected but no small size colonies were observed. Both suppressors produced partial defects in sexual reproduction and both suppressed an apsA deletion mutation. In wild-type background the mutant loci affected hyphal growth rate (samA) or changed the colony morphology (samB) and inhibited sexual spore formation (samA and samB). Only subtle effects on conidiation were found. We conclude that both suppressor genes bypass the apsA function and are involved in microtubule-dependent processes.

Aspergillus nidulans↗