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M Zulauf

Publications and source records attributed to M Zulauf.

At least 37 records · Page 2Linked to original sources
PubMed1997

[Optimizing the distribution and test locations in statistical perimetry. Preliminary results].

BACKGROUND: Are short programs useful to glaucoma-screening? We investigated the concept of Program G1x with Octopus 1-2-3, which permits examination of various numbers of test locations i.e., 16, 32, 45, or all 59 test locations. PATIENTS AND METHODS: Using 99 visual fields of glaucomatous or glaucoma-suspect right eyes, we compared mean defect (MD) and loss variance (LV) of the global visual field with MD and LV of the stages of G1x-program (standard strategy). RESULTS: The results showed that stage 1 of Program G1x underestimated the glaucomatous visual field damage present in the entire field. CONCLUSIONS: Thus, the use of only the first stage (16 test locations) of G1x is not advisable. At least 32 test locations, i.e., stages 1 and 2 of program G1x, are recommended for clinical perimetry.

Adult↗
PubMed1996

The micelle to vesicle transition of lipids and detergents in the presence of a membrane protein: towards a rationale for 2D crystallization.

The assembly of two-dimensional membrane protein crystals in the presence of lipids was analyzed with quasielastic light scattering and electron microscopy. Mixtures of detergent-solubilized lipids and/or proteins were submitted to slow or rapid dilution while measuring the hydrodynamic radii of the aggregates. Lipids alone exhibited lambda-shaped dilution curves with intermediate rod-shaped particles that converted into small vesicles. Depending on the protein-protein and protein-lipid interactions, detergent-solubilized protein-lipid mixtures showed a sharp transition from micelles to large densely packed proteoliposomes. Electron microscopy revealed that formation of crystals occurred shortly after this phase transition.

Crystallization↗
PubMed1996

Recombinant human renin produced in different expression systems: biochemical properties and 3D structure.

Human renin has been expressed in Sf9 and CHO cells using two different gene constructs. The first construct contained a foreign signal peptide fused directly to the sequence encoding mature renin, whereas the second construct harbors the sequence for preprorenin. Prorenin was produced in significantly higher amounts than the mature enzyme expressed without its propeptide in both expression systems. Both directly expressed mature renin and proteolytically derived active renin have been purified and cocrystallized with the renin inhibitor Ro 42-5892. The 3D structure has been solved for both versions and demonstrates identity despite different glycosylation and different N termini.

Amino Acid Sequence↗
PubMed1996

[Perimetry with normal Octopus technique and Weber 'dynamic' technique. Initial results with reference to reproducibility of measurements in glaucoma patients].

UNLABELLED: There is ample reason to strive for a shorter test without losing solid and reproducible information on the function of the eye. The purpose of this study was to compare the standard Octopus strategy with the 'dynamic strategy' of Weber in terms of time requirement and reproducibility of results, i.e., short-term as well as long-term fluctuations in glaucoma. MATERIALS AND METHODS: On an Octopus 1-2-3 automated perimeter, 23 experienced glaucoma patients with predominantly local loss completed three test sessions, each consisting of a short training test followed by six visual fields, i.e., the first 'stage' (16 test locations) of program GIX, beginning at random with one strategy, then alternating the strategies. RESULTS: The deviation from normal values of the 1104 test locations obtained with the standard and the dynamic strategy (mean +/- SD) was 5.2 +/- 7.5 dB and 4.6 +/- 7.3 dB (P < 0.02), respectively. The short-term fluctuation (given as variance) with the standard and the dynamic strategy averaged 8.3 +/- 5.9 dB2 and 10.2 +/- 5.8 dB2 (p < 0.02), respectively. The long-term fluctuation, i.e., 'test-to-test' variation (given as variance), with the standard and the dynamic strategy was 6.4 +/- 16.5 dB2 and 7.89 +/- 19.2 dB2 (P < 0.22), respectively. The total long-term fluctuation of the index mean defect, MD, averaged 1.8 +/- 2.7 dB2 and 1.3 +/- 1.7 dB2 (P = 0.69), respectively, with the standard and the dynamic strategy. The number or stimuli required with the standard and the dynamic strategy averaged 5.6 +/- 1.4 and 3.0 +/- 1.0 (P < 0.001), respectively. CONCLUSIONS: The dynamic strategy required 43% fewer stimuli and presented 23% (significantly) higher short-term fluctuation, but long-term fluctuations were similar for both strategies. The two strategies were comparable regarding the respective reproducibility of the results. However, further studies may investigate the sensitivity and the specificity of either strategy to distinguish disease from normal, or, change during a follow-up of a disease, and, may elucidate whether the observed differences between the two strategies are due to the modified step size, or, to the single (versus double) crossing of the threshold.

Adult↗
PubMed1995

Detergent structure in tetragonal crystals of OmpF porin.

BACKGROUND: The high-resolution structures of five porins have been solved by X-ray crystallography including the trigonal crystal form of the trimeric OmpF porin from Escherichia coli. In an accompanying article, the structure of the tetragonal form of OmpF porin is presented. In contrast to the trigonal crystal form, the protein surfaces normally in contact with lipids in the membrane are exposed and interact with amphiphiles in the tetragonal crystal. Thus, the tetragonal form can be used to investigate protein-detergent interactions. RESULTS: Using single-crystal neutron diffraction studies and two different detergents (one of them deuterated in its hydrophobic moiety), details of the amphiphile-protein interactions are revealed. Detergent molecules bind to the so-called hydrophobic zone that surrounds the OmpF porin trimer and which is exposed to lipid in the native environment. The aromatic rings on both sides of the hydrophobic zone coincide with the boundary between non-polar and polar moieties of the detergents. CONCLUSIONS: In the tetragonal crystal form of OmpF porin, the membrane-exposed area is accessible from the aqueous solution. It is coated by a film of detergent molecules, which presumably mimics the interactions of the protein with lipids in the biological membrane. In the trigonal form, protein-protein interactions predominate in the hydrophobic zone. These may reflect the tight interactions between trimers that are observed in the biological membrane.

Bacterial Outer Membrane Proteins↗
PubMed1995

Interferon gamma receptor extracellular domain expressed as IgG fusion protein in Chinese hamster ovary cells. Purification, biochemical characterization, and stoichiometry of binding.

Agents that antagonize the functions of interferon gamma (IFN gamma) are potential pharmaceuticals against several immunological and inflammatory disorders. IFN gamma receptor-immunoglobulin G fusion proteins (IFN gamma R-IgG) function as antagonists of endogenous IFN gamma and have longer half-lives in vivo in comparison with soluble IFN gamma receptors (sIFN gamma R), consisting of the extracellular region of the native sequence. A fusion protein comprising the extracellular domain of the human IFN gamma receptor and the hinge, CH2 and CH3 domains of the human IgG3 constant region, was expressed in Chinese hamster ovary cells. The IFN gamma R-IgG3 fusion protein was secreted into the culture medium as a 175-kDa glycoprotein and was purified over Protein G-Sepharose, DEAE-Sepharose, and size exclusion chromatography. IFN gamma R-IgG3 bound IFN gamma in solid phase assays and ligand blots, competed for the binding of radiolabeled IFN gamma to the cell surface receptor of Raji cells, and inhibited the IFN gamma-mediated antiviral activity with an efficiency at least one order of magnitude higher than that of the soluble receptor produced in the same expression system. Two IFN gamma R-IgG3 fusion proteins bound two IFN gamma dimers forming a complex of approximately 380 kDa. In immunodiffusion assays, the IFN gamma R-IgG3 fusion protein did not precipitate IFN gamma. Dissociation of bound IFN gamma from IFN gamma R-IgG3 was 2-fold slower than from the sIFN gamma R produced in insect cells.

Animals↗
PubMed1995

A 17-kDa CD4-binding glycoprotein present in human seminal plasma and in breast tumor cells.

We previously isolated gp17, a human seminal plasma glycoprotein, which specifically interacts with the D1-D2 region of CD4, a T cell surface molecule involved in antigen recognition mediated by helper T cells also acting as a receptor for the human immunodeficiency virus. In this study we report that monoclonal antibodies (mAb) reacting with gp17 are able to inhibit the binding of gp17 to immobilized soluble CD4. An immunohistochemical analysis shows that gp17 is also expressed in mammary tumor cells upon hormone treatment and in biopsies from breast cancer patients. A structural characterization of gp17, including amino acid sequencing, indicates that the protein has an extensive structural similarity with a glycoprotein designated as seminal actin-binding protein (SABP), also secreted by male sexual glands. SABP is in turn identical to gross cystic disease fluid protein-15 (GCDFP-15) or prolactin-inducible protein (PIP), a factor known as a highly specific and sensitive marker of primary and metastatic apocrine breast cancer. To establish further the correspondence of gp17 and GCDFP-15/PIP/SABP, the latter was expressed in bacteria from a cloned cDNA and purified by affinity chromatography to either anti-gp17 mAb-Sepharose or CD4-Sepharose. The purified recombinant protein is shown to inhibit the binding of labeled, pure g17 to immobilized soluble CD4. The finding that breast cancer cells express a protein able to interact with the CD4 domains involved in the recognition of class II major histocompatibility antigens suggests a possible mechanism by which a tumor may affect the activity of tumor-infiltrated CD4+ T cells.

Amino Acid Sequence↗
PubMed1995

A biotechnological method provides access to aggregation competent monomeric Alzheimer's 1-42 residue amyloid peptide.

Senile plaques, a neuropathological hallmark of Alzheimer's disease, consist primarily of insoluble aggregates of beta-amyloid peptide (A beta). A 42-residue peptide (A beta 1-42) appears to be the predominant form. In contrast to A beta 1-40, A beta 1-42 is characterized by its extreme tendency to aggregate into fibers or precipitate. A tailored biotechnological method prevents aggregation of A beta 1-42 monomers during its production. The method is based on a protein tail fused to the amino terminus of A beta. This tail leads to a high expression in E. coli, and a histidine affinity tag facilitates purification. Selective cleavage of the fusion tail is performed with cyanogen bromide by immobilizing the fusion protein on a reversed phase chromatography column. Cleavage then occurs only at the methionine positioned at the designed site but not at the methionine contained in the membrane anchor sequence of A beta. Furthermore, immobilization prevents aggregation of cleaved A beta. Elution from the HPLC column and all succeeding purification steps are optimized to preserve A beta 1-42 as a monomer. Solutions of monomeric A beta 1-42 spontaneously aggregate into fibers within hours. This permits the investigation of the transition of monomers into fibers and the correlation of physico-chemical properties with biological activities. Mutations of A beta 1-42 at position 35 influence the aggregation properties. Wild-type A beta 1-42 with methionine at position 35 has similar properties as A beta with a methionine sulfoxide residue. The fiber formation tendency, however, is reduced when position 35 is occupied by a glutamine, serine, leucine, or a glutamic acid residue.

Amino Acid Sequence↗
PubMed1994

The influence of patient reliability on visual field outcome.

The reliability of subjects to perform to perimetry correctly should be carefully evaluated to interpret visual field examinations adequately. Clinicians generally agree that numerous false-positive responses to catch trials cause measured thresholds to be falsely high and numerous false-negative responses cause measured thresholds to be falsely low. We studied the effect of false-positive and false-negative responses on the outcome of visual field measurements. Of 47 eyes, the results of 106 stable glaucomatous visual field tests (Program G1, Octopus 201, Interzeag, Schlieren, Switzerland) with false-positive responses and no more than one false-negative response to catch trials were compared to the results of reliable visual field tests (no false-positive and no more than one false-negative response) performed on the same eye. Similarly, 60 stable visual fields with false-negative responses and no more than one false-positive response were used to study the effect of false-negative responses on visual field sensitivities. Linear regression analysis disclosed a mean sensitivity increase of 1.5 dB for every 10% of false-positive responses (r = .34, P = .000) and a mean sensitivity decrease of 1.2 dB for every 10% of false-negative responses (r = .26, P = .04). These results may be used to help reduce the magnitude of unexplained long-term fluctuation in visual field interpretation.

Adult↗
PubMed1994

Normal visual fields measured with Octopus Program G1. I. Differential light sensitivity at individual test locations.

Exact knowledge of the normal variation of visual fields and the influence of age upon them is essential to differentiate normal from abnormal results, e.g., in glaucoma suspects. This study evaluates the normal variability of differential light sensitivity at individual test locations and incorporates a data base of a multicenter study performed with Octopus 201 perimeters using Program G1. The 824 fields thus obtained included 139 fields of 139 healthy volunteers who had undergone two previous visual fields and completed all three phases of the program. Sensitivity decreased linearly with age, an effect which for individual test locations ranged between 0.036 and 0.107 dB/year and which became more pronounced towards the periphery. On average, the age-related effects explained only 17% of the interindividual variation (range 4%-31%). The interindividual variation within a test averaged 4.6 dB2 and revealed a moderate, but quadratic increase towards the periphery. The intra-individual short-term variation was considerably lower, averaging 2.2 dB2. There was a similar modest, quadratic increase of the intra-individual variation towards the periphery. The results may help distinguish incipient disease manifestations from normal variation of perimetric results. Furthermore, the results give insight into the calculation of global visual field indices.

Adult↗
PubMed1994

Normal visual fields measured with Octopus-Program G1. II. Global visual field indices.

To complement results from individual test locations, clinicians also evaluate indices, as they give a succinct overview of the visual field. This, however, requires exact knowledge of their variability. The present study was designed to determine normal interindividual variability of global visual field indices and incorporates a data base of a multicenter study performed with Octopus 201 perimeters using Program G1. The 824 fields thus obtained included 139 fields of 139 healthy volunteers who had undergone two previous visual fields and completed all three phases of program G1. The index mean sensitivity showed a significant and linear decrease with increasing age, 0.064 dB/year of life. The indices loss variance, corrected loss variance, and short-term fluctuation did not correlate significantly with age. Percentiles are given for these visual field indices. While within the limits of normal values provided by the manufacturer for these indices, these results suggest that visual fields with "borderline" values require further clinical investigation in reliable, experienced subjects. The results may help clinicians to better evaluate global visual field indices and, therefore, to detect loss of visual function earlier.

Adult↗
PubMed1994

[Pupil perimetry with the Octopus 1-2-3. Initial experiences].

PURPOSE: Development of a clinically useful pupil perimetry on an OCTOPUS 1-2-3. MATERIALS AND METHODS: Various test parameters were investigated on a moderately modified OCTOPUS 1-2-3. We evaluated the pupillary responses of 122 eyes of 122 healthy volunteers qualitatively. RESULTS: Pleasing pupillary responses were obtained with the following parameters: 200 ms stimuli, Goldmann size 5 (1.5 degrees), background illumination 3 apostilb. Acoustic signals 0.5 seconds before stimulus presentation were helpful to minimize blinking artifacts. The pupillary reactions were fare stronger in central areas of the visual field than in mid-peripheral areas (i.e. 26 degrees). CONCLUSIONS: Pupil perimetry can be preformed on a moderately modified OCTOPUS 1-2-3. The results reveal considerable inter- and intra-individual variability. Equal pupillary responses at all eccentricities would improve subsequent mathematical evaluation.

Adult↗
PubMed1994

[Indications for stimulus 3 and 5 in automatic perimetry. Preliminary results].

PURPOSE: Goldmann stimulus size 3 and 5 were studied with automated perimetry in glaucoma patients to help develop specific guidelines for their use. METHODS: We examined 49 eyes of 49 glaucoma patients with both stimulus sizes 3 and 5 with Program G1 (all phases) of the Octopus 500 Perimeter. Fields were preformed sequentially, in random order, at the same sitting. RESULTS: The means of the indices for stimulus size 3 (+/- = standard deviation) were: Mean sensitivity 18.8 +/- 4.7 dB; loss variance 45.0 +/- 42.0 dB2; short-term fluctuation 2.1 +/- 0.45 dB. With stimulus size 5, mean sensitivity increased (Wilcoxon: p < 0.0005) by 8.1 +/- 1.7 dB, and short-term fluctuation decreased (Wilcoxon: p < 0.0005) by 0.3 +/- 0.6 dB. Scotomas measured with stimulus size 5 were shallower than with stimulus size 3, i.e., the pattern of visual field defects was better represented by stimulus size 3 in 13 eyes. Stimulus size 5 was preferred in 14 eyes because more information was available in the area of absolute scotomas. In 6 eyes, deep scotomas within 4 degrees of fixation were seriously underestimated with the larger stimulus. CONCLUSIONS: Stimulus size 5 should be used if more than 10% of test locations have absolute scotomas or the mean sensitivity falls below 15 dB with stimulus size 3. Complementary central fields with stimulus size 3 fields should be used when evaluation of the central field shows relative scotomas with either stimulus.

Aged↗
PubMed1993

An evaluation of clusters in the glaucomatous visual field.

We used a statistical cluster analysis to analyze patterns of loss in 76 visual fields with typical glaucomatous defects to identify natural groupings of test locations in the visual field. Eleven clusters in the Octopus Program G1 (Interzeag, Inc., Northboro, Massachusetts) visual field were thus defined. In a separate population of 70 early glaucomatous and 70 age-matched normal visual fields, the local mean defects within these clusters and the global mean defect were calculated to assess their relative abilities to discriminate between the two groups. The 11 clustered mean defects collectively had a sensitivity of 90% and a specificity of 93%; the global mean defect had a sensitivity of 81% and a specificity of 91%. Additionally, we examined the long-term fluctuation clusters of test locations compared to the long-term fluctuation of individual test locations. Four hundred ten visual fields of 93 clinically stable eyes of 67 patients with glaucoma, as well as 210 visual fields of 105 eyes of 105 normal subjects were studied. In the stable glaucoma group, mean fluctuation of clustered test locations was 3.5 dB2, and mean fluctuation of individual test locations was 7.0 dB2. In the normal group, the respective values were 0.6 dB2 and 1.8 dB2. Cluster analysis was effective in detecting localized loss and in dampening long-term fluctuation. We studied the use of clusters in distinguishing normal from glaucomatous as well as stable from deteriorating visual fields.

Adult↗
PubMed1993

Expression, purification and crystallization of fully active, glycosylated human interleukin-5.

Recombinant human interleukin-5 (hIL-5) has been expressed at high levels and produced in large quantities in baculovirus infected Sf9 insect cells. The glycosylated protein was purified using immuno-affinity chromatography and gel filtration. Purified hIL-5 has been crystallized using standard vapour diffusion techniques with PEG as a coprecipitant. The crystals belong to the C2 space group and diffract to 2 A.

Animals↗
PubMed1993

Correlation of spatial contrast sensitivity and visual fields in glaucoma.

Perimetry is the standard examination in glaucoma, whereas contrast sensitivity is often proposed as a complementary test. This study investigates the extent to which the outcomes of the two tests correlate. One eye each of 44 glaucoma patients and 16 glaucoma suspects was tested with the Haag-Streit Visometer and the Octopus 201 perimeter (program G1). Contrast sensitivities correlated highest with the center of the visual field (Spearman's rho = 0.76; P < 0.001) and slightly less with the mean sensitivity of the entire visual field (rho = 0.63; P < 0.001). Mean contrast sensitivity correlated weakly with the square root of corrected loss variance (rho = -0.45; P < 0.001) and short-term fluctuation (rho = -0.34; P < 0.007). The two tests differed considerably only in very few patients. We recommend careful evaluation of the central area of glaucomatous visual fields whenever contrast sensitivity testing is not available.

Contrast Sensitivity↗
PubMed1993

Priority of test locations for automated perimetry in glaucoma.

PURPOSE: Static threshold automated perimetry is a demanding test which can be tiring for some patients. The authors investigate how to optimize early stages of the test which can shorten examination time and improve performance. The effectiveness of measuring every point twice to improve diagnostic precision (proportion of eyes correctly diagnosed as normal or glaucomatous) also was evaluated. METHODS: The authors evaluated the relative contributions of individual test locations to the sensitivity and specificity of static threshold perimetry. One hundred visual fields (Octopus Program G1) of 100 patients with open-angle glaucoma and early glaucomatous defects were used to rank the most frequently defective test locations. This sequence was modified so that highly correlated points were not ranked together. The sensitivities and specificities of the defined sequence of test presentations were then measured in a separate database of 70 normal controls and 70 patients with early glaucomatous visual field defects. RESULTS: Sensitivity and specificity were, respectively, 80% and 80% after 12 locations, 89% and 89% after 26 locations, and 97% and 99% after all 59 test locations. The information obtained with the first phase alone approximates that of both phases. CONCLUSION: Staging of locations tested with automated perimetry in glaucoma may be a valuable method to reduce examination time, minimize fatigue effects, and optimize diagnostic information. Retesting every point does not improve diagnostic precision.

Glaucoma, Open-Angle↗