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S Ernst

Publications and source records attributed to S Ernst.

At least 73 records · Page 4Linked to original sources
PubMed1997

On the regulation of fibroblast growth factor activity by heparin-like glycosaminoglycans.

The activity of several angiogenic factors, like fibroblast growth factors (FGF), is modulated by heparin-like glycosaminoglycans (HLGAGs), which are acidic polysaccharides present in the extracellular matrix and at the cell surface. FGF binds to HLGAG in the matrix, where it is sequestered in a protected and inactive form, and at the cell surface, where it activates its cognate signaling receptor. Here we review recent progress in elucidating how HLGAG regulates FGF-induced signal transduction. Data from crystal structures of FGF complexed to active and inactive oligosaccharides is analyzed in the context of current models for HLGAG modulation of FGF activity. We propose that FGF can dimerize in several different modes, stabilized by HLGAGs. Individual dimer modes may represent active or inactive FGF and it is possible that different HLGAGs preferentially stabilize different FGF dimer modes. Understanding HLGAG-FGF interactions can provide leverage for new approaches to therapeutic control of angiogenesis.

Journal Article↗
PubMed1997

[31P-MR spectroscopy of the human liver--the spectral indications of lymphoma infiltration].

PURPOSE: To evaluate whether phosphorus magnetic resonance spectroscopy (31P-MRS) enables a non-invasive detection of liver involvement in systemic diseases like Hodgkin's lymphoma. MATERIALS AND METHODS: Using a clinical 1.5 Tesla whole-body MR system image-guided localised phosphorus MR spectra from the anatomically defined volumes of interests were measured. A combination of surface coil, adiabatic excitation pulse and modified image-selected in vivo spectroscopy (ISIS)-sequence was applied. The spectroscopy data were evaluated quantitatively with a time-domain fit programme using non-linear optimisation algorithms to quantify peak areas. After establishment of the examination protocol, 22 healthy volunteers and 13 patients with suspected lymphoma infiltration of the liver were examined. RESULTS: Liver spectra of patients suffering from lymphoma infiltration differed significantly from spectra of persons with normal liver: 1. The peak area ratio of phosphomonoesters (PME) to beta-NTP was elevated in all patients with histologically confirmed liver lymphoma. 2. Patients suffering from Hodgkin's disease with specific or unspecific liver infiltration (n = 7) could be differentiated from patients without liver involvement. In case of infiltrated liver, the peak area ratio PME to beta-NTP was increased, and the pH value was shifted to lower values. Unambiguous differentiation between non-specific (n = 3) and specific (n = 4) infiltration of the liver was not possible. 3. In patients after cytostatic treatment (n = 3), an increase of the peak area ratio of inorganic phosphate to beta-NTP was observed. CONCLUSIONS: Our preliminary results indicate that 31P-MRS can yield pointers to liver involvement in patients with systemic diseases such as Hodgkin's disease, which may be hardly detected by imaging methods.

Adolescent↗
PubMed1997

Analysis of human sperm karyotypes in testicular cancer patients before and after chemotherapy.

Sperm karyotype analysis was performed on testicular cancer patients before and after treatment with BEP (bleomycin, etoposide, and cisplatin). A total of 788 sperm chromosome complements was studied, 236 before chemotherapy (CT) and 552 post-CT. There was no significant difference in the total frequency of sperm chromosomal abnormalities pre-CT (10.2%) compared to post-CT (10.7%). Similarly, there were no significant differences in the frequencies of numerical abnormalities (2.5% pre-CT vs. 2.4% post-CT) or structural abnormalities (6.4% pre-CT vs. 7.4% post-CT). The percentage of X-bearing sperm was also not significantly different before (46.3%) and after CT (50.1%). The results in cancer patients were not significantly different from those in control donors. This study corroborates results from our previous analysis of these same men using multicolor fluorescence in situ hybridization for assessment of aneuploidy for chromosomes 1, 12, X, Y, and XY. Together, these two studies suggest that the sperm of men receiving BEP chemotherapy are not at increased risk of chromosomal abnormalities two or more years after treatment.

Adult↗
PubMed1997

Ontogeny of electrically evoked brain stem potentials in neonatally deafened gerbils (Meriones unguiculatus) after cochlear implantation.

To investigate the ontogeny of the electrically evoked auditory brainstem response (E-ABR) we used an animal model of neonatally deafened gerbils with an intracochlear implanted electrode. The E-ABR were recorded in three groups: normal hearing animals (NORM) and binaural deafened without chronical electrostimulation (BD) in comparison to binaural deafened animals with chronical stimulation (BDS). In group BD the deafening lead to inter-peak-latency II-V increase and histological degeneration in the Cochlear Nucleus. In chronical stimulated animals (BDS) we could not observe significant differences compared to unstimulated gerbils until the day after birth. In further studies longer stimulation periods, recordings of electrically evoked middle latency response as well as histological examinations of more central parts of the auditory pathway will be included.

Animals↗
PubMed1996

Expression in Escherichia coli, purification and characterization of heparinase I from Flavobacterium heparinum.

The use of heparin for extracorporeal therapies has been problematical due to haemorrhagic complications; as a consequence, heparinase I from Flavobacterium heparinum is used for the determination of plasma heparin and for elimination of heparin from circulation. Here we report the expression of recombinant heparinase I in Escherichia coli, purification to homogeneity and characterization of the purified enzyme. Heparinase I was expressed with an N-terminal histidine tag. The enzyme was insoluble and inactive, but could be refolded, and was purified to homogeneity by nickel-chelate chromatography. The cumulative yield was 43%, and the recovery of purified heparinase I was 14.4 mg/l of culture. The N-terminal sequence and the molecular mass as analysed by matrix-assisted laser desorption MS were consistent with predictions from the heparinase I gene structure. The reverse-phase HPLC profile of the tryptic digest, the Michaelis-Menten constant Km (47 micrograms/ml) and the specific activity (117 units/mg) of purified recombinant heparinase I were similar to those of the native enzyme. Degradation of heparin by heparinase I results in a characteristic product distribution, which is different from those obtained by degradation with heparinase II or III from F. heparinum. We developed a rapid anion-exchange HPLC method to separate the products of enzymic heparin degradation, using POROS perfusion chromatography media. Separation of characteristic di-, tetra- and hexa-saccharide products is performed in 10 min. These methods for the expression, purification and analysis of recombinant heparinase I may facilitate further development of heparinase I-based medical therapies as well as further investigation of the structures of heparin and heparan sulphate and their role in the extracellular matrix.

Amino Acid Sequence↗
PubMed1996

Heparinase I from Flavobacterium heparinum. Mapping and characterization of the heparin binding domain.

In this study we have identified the primary heparin binding site of heparinase I (EC 4.2.2.7). Chemical and proteolytic digests of heparinase I were used in direct binding and competition assays, to map the regions of heparinase I that interact specifically with heparin. We find the heparin binding site contains two Cardin-Weintraub heparin binding consensus sequences and a calcium co-ordination consensus motif. We show that heparin binding to heparinase I is independent of calcium (Kd of 60 nm) and that calcium is able to activate heparinase I catalytically. We find that sulfhydryl selective labeling of cysteine 135 of heparinase I protects the lysines of the heparin binding sequence from proteolytic cleavage, suggesting the close proximity of the heparin binding site to the active site. Site-directed mutagenesis of H203A (contained in the heparin binding site) inactivated heparinase I; however, a H203D mutant retained marginal activity, indicating a role for this residue in catalysis. The above results taken together suggest that histidine 203 (hence the heparin binding site) is immediately adjacent to the scissile bond. We propose that the heparin binding site and active site are in close proximity to each other and that the calcium coordination motif, contained in the heparin binding site, may bridge heparin to heparinase I through calcium in a ternary complex during catalysis.

Amino Acid Sequence↗
PubMed1996

An incremental dosing protocol for women with severe vaginal trichomoniasis and adverse reaction to metronidazole.

OBJECTIVE: Our purpose was to develop and test an incremental dosing protocol for women with adverse reaction to metronidazole and severe symptomatic Trichomonas vaginitis. STUDY DESIGN: Two women with documented Trichomonas infection and presumed metronidazole allergy were initially treated with a number of alternative methods without success. With persistent severe symptoms associated with their infection, these women were admitted to the hospital and underwent an intravenous incremental metronidazole dosing protocol. RESULTS: Both patients were successfully treated without adverse event. They are both symptom-free and apparently cured several months after treatment. CONCLUSION: This protocol offers a new therapeutic option to women with adverse metronidazole reactions and severe symptomatic Trichomonas vaginitis resistant to treatment with nonmetronidazole therapy.

Antitrichomonal Agents↗
PubMed1996

[The computed tomography of acute sigmoid diverticulitis].

PURPOSE: To study the ranking of CT in the diagnosis of sigma diverticulitis. Comparison of results of the colon monocontrast enema with those obtained via CT and histopathology as gold standard. MATERIAL AND METHODS: 32 patients were included who were operated on for sigma diverticulitis. In 30 patients both CT and monocontrast enema were performed and in two patients CT only. RESULTS: Acute inflammatory wall alterations are identified by CT with a sensitivity of 89.7% vs 96.3% via contrast enema. Pericolic reactions of the environment were seen via CT with 89.7% sensitivity. In case of covered perforations CT yielded a sensitivity of 76.5% vs 46.7% via contrast enema. Sensitivity for abscesses and fistulas was in each case 100% with CT. RESULTS: CT may help to identify extraluminal inflammatory changes and complications in diverticulitis. The degree of the inflammation can be classified and the surgical approach suitably influenced, respectively modified.

Acute Disease↗
PubMed1996

[The radiological findings in surgically and conservatively treated intracranial arachnoid cysts].

PURPOSE: To determine which appearances on CT or MRI are indications for surgical treatment of intracranial arachnoid cysts. METHOD: The images obtained from 26 patients treated either by surgery or conservatively were compared retrospectively. The features evaluated were the size of the cyst, evidence of a space-occupying lesion, cerebral abnormalities near the cyst and skull deformities. RESULTS: In 6 patients (23%), surgical treatment was indicated because of the presence of obstructive hydrocephalus. The presence of all other radiological findings did not differ significantly between the two analysed groups. 92% of the patients treated surgically benefited from the treatment. Fenestration and shunting produced similar results in respect to reduction in size of the cyst and the clinical and neurological symptoms. CONCLUSION: The only indication for surgery is the presence of obstructive hydrocephalus. The other features were seen equally amongst the patients treated conservatively and the surgical patients and had no influence on the decision to operate.

Adolescent↗
PubMed1996

Sequences of beta-lactamase genes encoding CTX-M-1 (MEN-1) and CTX-M-2 and relationship of their amino acid sequences with those of other beta-lactamases.

Amino acid sequences determined either by protein sequencing or by DNA sequencing are identical for cefotaximases CTX-M-1 and MEN-1, whereas CTX-M-2 is 84% identical to CTX-M-1/MEN-1. Both beta-lactamases are distantly related to other plasmidic class A enzymes (homology to TEM-1 is 38.1% for CTX-M-1/MEN-1 and 36.5% for CTX-M-2); the closest relationship was with the chromosomal beta-lactamase of Klebsiella oxytoca E23004 (homologies of 74.5% for CTX-M-1/MEN-1 and 77.9% for CTX-M-2). The cefotaximases CTX-M-1/MEN-1 and CTX-M-2 represent two members of a new subgroup of plasmidic class A beta-lactamases.

Amino Acid Sequence↗
PubMed1995

Crystallographic structure of a PLP-dependent ornithine decarboxylase from Lactobacillus 30a to 3.0 A resolution.

Ornithine decarboxylase from Lactobacillus 30a (L30a OrnDC) is representative of the large, pyridoxal-5'-phosphate-dependent decarboxylases that act on lysine, arginine or ornithine. The crystal structure of the L30a OrnDC has been solved to 3.0 A resolution using MIR phases in combination with density modification (space group P6; a = 195.6 A, c = 97.6 A; dimer of 1460 amino acid residues/asymmetric unit; VM = 3.26 A3/Da). The refined crystallographic R-value was 0.219 (Rfree = 0.268) using 2-fold restraints with a 4 sigma cutoff and 8.0 to 3.0 A resolution data. Six dimers related by C6 symmetry compose the enzymatically active dodecamer (approximately 10(6) Da). Each monomer of L30a OrnDC can be described in terms of five sequential folding domains. The amino-terminal domain, residues 1 to 107, consists of a five-stranded beta-sheet termed the "wing" domain. Two wing domains of each dimer project inward towards the center of the dodecamer and contribute to dodecamer stabilization. The "linker" domain, residues 108 to 160, consists of short alpha-helices separated by a loop that fills in the PLP pocket. The third domain, residues 161 to 413, is an alpha/beta domain containing a seven stranded beta-sheet that resembles the PLP-binding domain of the aspartate aminotransferases. The fourth domain, residues 414 to 569, resembles the "small" domain of the aspartate aminotransferases, but is significantly larger due to insertions. The remaining carboxy-terminal domain, residues 570 to 730, is organized into multiple antiparallel loops and seven alpha-helices that help form a deep channel leading to the PLP-binding site.

Amino Acid Sequence↗
PubMed1995

Enzymatic degradation of glycosaminoglycans.

Glycosaminoglycans (GAGs) play an intricate role in the extracellular matrix (ECM), not only as soluble components and polyelectrolytes, but also by specific interactions with growth factors and other transient components of the ECM. Modifications of GAG chains, such as isomerization, sulfation, and acetylation, generate the chemical specificity of GAGs. GAGs can be depolymerized enzymatically either by eliminative cleavage with lyases (EC 4.2.2.-) or by hydrolytic cleavage with hydrolases (EC 3.2.1.-). Often, these enzymes are specific for residues in the polysaccharide chain with certain modifications. As such, the enzymes can serve as tools for studying the physiological effect of residue modifications and as models at the molecular level of protein-GAG recognition. This review examines the structure of the substrates, the properties of enzymatic degradation, and the enzyme substrate-interactions at a molecular level. The primary structure of several GAGs is organized macroscopically by segregation into alternating blocks of specific sulfation patterns and microscopically by formation of oligosaccharide sequences with specific binding functions. Among GAGs, considerable dermatan sulfate, heparin and heparan sulfate show conformational flexibility in solution. They elicit sequence-specific interactions with enzymes that degrade them, as well as with other proteins, however, the effect of conformational flexibility on protein-GAG interactions is not clear. Recent findings have established empirical rules of substrate specificity and elucidated molecular mechanisms of enzyme-substrate interactions for enzymes that degrade GAGs. Here we propose that local formation of polysaccharide secondary structure is determined by the immediate sequence environment within the GAG polymer, and that this secondary structure, in turn, governs the binding and catalytic interactions between proteins and GAGs.

Animals↗