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Biomedical subjects

G Maass

Publications and source records attributed to G Maass.

At least 73 records · Page 4Linked to original sources
PubMed1990

Marker haplotype association with growth in German cystic fibrosis patients.

In 84 families with 101 children with cystic fibrosis (CF) and 103 unaffected siblings, the haplotype of CF chromosomes was determined with six restriction fragment length polymorphism (RFLP) markers that span the CF gene locus. Patient groups with different genotypes in the more distant flanking marker loci MET D, MET H, and D7S8 differed significantly from each other with respect to percentile height and weight, and percentage of weight for height. Patients homozygous 1-1 in met D (TaqI) and met H (TaqI) were thin and tall when homozygous 1-1 in J3.11 (MspI), and small when homozygous 2-2 in J3.11. Heterozygosity in 3.11 and met H and homozygosity 1-1 in met D segregated with the most severe growth retardation. In contrast, growth was normal in patients who were heterozygous in met D and/or had an uncommon KM.19/XV-2c haplotype. Most patients with pancreatic sufficiency and/or borderline sweat test values were carrying rare haplotypes on their CF chromosomes. Adult patients clustered in genotype groups with normal height percentile distributions. This association between haplotype and clinical severity of CF in the German population provides evidence for genetic microheterogeneity of the CF locus, either because of the existence of multiple alleles of the CF gene itself and/or because of the existence of closely linked polymorphic genes that control growth and development and hence modulate the clinical course and prognosis of CF.

Adolescent↗
PubMed1990

Frequency of the F508 deletion in the CFTR gene in Turkish cystic fibrosis patients.

The F508 deletion in the cystic fibrosis transmembrane conductance regulator (CFTR) gene was found in 8 out of 30 Turkish cystic fibrosis (CF) chromosomes (27%). Five Turkish delta F508 CF chromosomes were associated with the risk haplotype B in KM19 (2 allele)/XV2c (1 allele). In the Turkish population, cystic fibrosis is predominantly caused by mutations other than the F508 deletion.

Chromosome Deletion↗
PubMed1990

Measles-mumps vaccination in the FRG: an empirical analysis after 14 years of use. I. Efficacy and analysis of vaccine failures.

One hundred and ninety two reports on vaccine failures after measles and mumps vaccination are analysed. These reports were received by the Drug Surveillance Department at Behringwerke between 1976 and 1989. Seventy-six per cent of the suspected measles and 41% of the suspected mumps cases occurred within the first 3 years postvaccination. Most probably these were primary vaccine failures. The analysis of the data collected in the 14 years since the introduction of measles-mumps vaccination in the FRG gives no reason to suspect that the protection afforded by the vaccines wanes with time.

Child↗
PubMed1990

Measles-mumps vaccination in the FRG: an empirical analysis after 14 years of use. II. Tolerability and analysis of spontaneously reported side effects.

Four hundred and thirty-three reports of suspected side effects following measles-mumps vaccination had been received at Behringwerke by the end of December 1989. The analysis of the data shows that no new risks of the vaccination could be identified and that the frequency of side effects is in good agreement with the findings of other authors. It therefore can be assumed that the relative risks of the vaccination continue to be distinctly outweighed by the benefits. The findings clearly demonstrate once more that it is necessary to carry out a thorough differential diagnosis before one can assume that the symptoms observed are causally related to the vaccination. In addition the analysis shows the importance of the epidemiological approach to the assessment of rare side effects.

Adult↗
PubMed1990

Infectious foot-and-mouth disease virus derived from a cloned full-length cDNA.

A full-length cDNA plasmid of foot-and-mouth disease virus has been constructed. RNA synthesized in vitro by means of a bacteriophage SP6 promoter inserted in front of the cDNA led to the production of infectious particles upon transfection of BHK-21 cells. These particles were also found to be highly infectious for primary bovine kidney cells as well as for baby mice. The difficulty in cloning the foot-and-mouth disease virus cytidyl tract in Escherichia coli was circumvented by joining two separate cloned parts, representing the S and L fragments of the genome, and, in a second step, inserting a dC-dG homopolymer. Homopolymeric sequences of up to 25 cytidyl residues did not lead to the production of virus. Replicons containing poly(C) tracts long enough to permit virus replication were first established in yeast cells. One of these constructs could also be maintained in E. coli and was used to produce infectious RNA in vitro. The length of the poly(C) sequence in this cDNA plasmid was 32 nucleotides. However, the poly(C) tracts of two recombinant viruses found in transfected BHK-21 cells were 60 and 80 nucleotides long, respectively. Possible mechanisms leading to the enlargement of the poly(C) tract during virus replication are discussed.

Animals↗
PubMed1989

Fluorescence stopped-flow kinetics of the cleavage of synthetic oligodeoxynucleotides by the EcoRI restriction endonuclease.

We have investigated in fluorescence stopped-flow and temperature-jump experiments the EcoRI-catalyzed cleavage of synthetic palindromic tridecadeoxynucleotides which contain the EcoRI site but differ in the flanking sequences. The overall reaction can be resolved in several reactions which were analyzed by a nonlinear least-squares fitting procedure on the experimental data. The result of this analysis is a minimal scheme that describes the overall reaction in terms of the rate constants of the individual reactions. According to this scheme EcoRI and the tridecadeoxynucleotide substrates associate in the presence of Mg2+ in a nearly diffusion-controlled process. This is followed by a reaction which is or includes the cleavage of the first phosphodiester bond. There is no indication for a time-resolved conformational transition prior to catalysis. After cleavage of the first strand, dissociation of the nicked double strand can occur, which then rearranges to the original palindromic double-stranded substrate and is bound again by the enzyme. Alternatively, the nicked double strand can be cleaved in the second strand. This reaction is followed by product release from the enzyme. The magnitude of the individual rate constants depends on the substrate used; the differences explain the preference of EcoRI for substrates that contain AT as compared to GC base pairs next to the recognition site.

Base Sequence↗
PubMed1989

Genetic engineering of EcoRI mutants with altered amino acid residues in the DNA binding site: physicochemical investigations give evidence for an altered monomer/dimer equilibrium for the Gln144Lys145 and Gln144Lys145Lys200 mutants.

We have genetically engineered the Arg200----Lys mutant, the Glu144Arg145----GlnLys double mutant, and the Glu144Arg145Arg200----GlnLysLys triple mutant of the EcoRI endonuclease in extension of previously published work on site-directed mutagenesis of the EcoRI endonuclease in which Glu144 had been exchanged for Gln and Arg145 for Lys [Wolfes et al. (1986) Nucleic Acids Res. 14, 9063]. All these mutants carry modifications in the DNA binding site. Mutant EcoRI proteins were purified to homogeneity and characterized by physicochemical techniques. All mutants have a very similar secondary structure composition. However, whereas the Lys200 mutant is not impaired in its capacity to form a dimer, the Gln144Lys145 and Gln144Lys145Lys200 mutants have a very much decreased propensity to form a dimer or tetramer depending on concentration as shown by gel filtration and analytical ultracentrifugation. This finding may explain the results of isoelectric focusing experiments which show that these two mutants have a considerably more basic pI than expected for a protein in which an acidic amino acid was replaced by a neutral one. Furthermore, while wild-type EcoRI and the Lys200 mutant are denatured in an irreversible manner upon heating to 60 degrees C, the thermal denaturation process as shown by circular dichroism spectroscopy is fully reversible with the Gln144Lys145 double mutant and the Gln144Lys145Lys200 triple mutant. All EcoRI endonuclease mutants described here have a residual enzymatic activity with wild-type specificity, since Escherichia coli cells overexpressing the mutant proteins can only survive in the presence of EcoRI methylase. The detailed analysis of the enzymatic activity and specificity of the purified mutant proteins is the subject of the accompanying paper [Alves et al. (1989) Biochemistry (following paper in this issue)].

Base Sequence↗
PubMed1989

Changing the hydrogen-bonding potential in the DNA binding site of EcoRI by site-directed mutagenesis drastically reduces the enzymatic activity, not, however, the preference of this restriction endonuclease for cleavage within the site-GAATTC-.

According to the X-ray structure analysis of an EcoRI-oligodeoxynucleotide complex [McClarin et al. (1986) Science 234, 1526], sequence specificity is mediated by 12 hydrogen bonds, 6 from each of the two identical subunits of the dimeric enzyme to the recognition site -GAATTC-: Arg200 forms two hydrogen bonds with guanine, while Glu144 and Arg145 form four hydrogen bonds to adjacent adenine residues. Changing the hydrogen-bonding potential at the recognition site without perturbing the rest of the interface should lead to the recognition of degenerate sequences [Rosenberg et al. (1987) in Protein Engineering (Oxender, D. L., & Fox, C. F., Eds.) pp 237-250, Liss, New York]. We have shown previously that replacing Glu144 by Gln and Arg145 by Lys affects the activity of the enzyme, not, however, its specificity [Wolfes et al. (1986) Nucleic Acids Res. 14, 9063]. We show now that also the mutation of Arg200 to Lys, the double mutation Glu144Arg145 to GlnLys, and the triple mutation Glu144Arg145Arg200 to GlnLysLys do not lead to a detectable degeneracy of the specificity of cleavage by EcoRI but significantly impair the catalytic activity of this enzyme. A detailed analysis of the steady-state kinetics of cleavage of pUC8 DNA and a tridecadeoxynucleotide substrate demonstrates that the reduction in activity for all DNA binding site mutants investigated so far is mainly due to a decrease in kcat, with the exception of the Arg200 to Lys mutant, which is only impaired in its KM.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1989

Modulation of the affinity of the single-stranded DNA-binding protein of Escherichia coli (E. coli SSB) to poly(dT) by site-directed mutagenesis.

A vector for site-directed mutagenesis and overproduction of the Escherichia coli single-stranded-DNA-binding protein (E. coli SSB) was constructed. An E. coli strain carrying this vector produces up to 400 mg pure protein from 25 g wet cells. The vector was used to mutate specifically the Phe60 residue of E. coli SSB. Phe60 had been proposed to be located near the single-stranded-DNA-binding site. Substitution of the Phe60 residue by Val, Ser, Leu, His, Tyr and Trp gave proteins with no or only minor conformational changes, as detected by NMR spectroscopy. The affinity of the mutant E. coli SSB proteins for single-stranded DNA decreased in the order Trp greater than Phe (wild-type) greater than Tyr greater than Leu greater than His greater than Val greater than Ser, leading to the conclusion that position 60 is a site of hydrophobic interaction of the protein with DNA.

Bacterial Proteins↗
PubMed1987

[HIV infection].

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Complexes of the single-stranded DNA-binding protein from Escherichia coli (Eco SSB) with poly(dT). An investigation of their structure and internal dynamics by means of electron microscopy and NMR.

Based on electron microscopy and NMR spectroscopy it is deduced that Eco SSB binds with moderate cooperativity to polynucleotides. Evidence is provided that the protein binds in its tetrameric form to the nucleic acid forming a nucleosome-like structure. NMR-spectroscopic analysis of the complexes shows that the carboxy-terminal region of the Eco SSB maintains a high flexibility even when the protein is immobilized in large protein-protein clusters.

Escherichia coli↗
PubMed1987

Interaction of polymyxin B nonapeptide with anionic phospholipids.

The interaction of polymyxin B nonapeptide (PMBN) and polymyxin B (PMB) with the anionic phospholipids phosphatidylserine (PS), dipalmitoylphosphatidylglycerol (DPPG), dipalmitoylphosphatidic acid (DPPA), and 1:1 mixtures (w/w) of DPPA and distearoylphosphatidylcholine (DSPC) was studied by calorimetry, electron spin resonance, and fluorescence spectrometry, electron microscopy, and fusion and leakage assays. The phase transition temperatures of DPPA and DPPG were very similar when bound to PMB or PMBN, indicating that the lipids are in a similar state when bound to the cationic peptides. Both PMB and PMBN caused the interdigitation of DPPG bilayers, suggesting that the penetration of hydrophobic side chains from a peptide bound electrostatically on the surface is sufficient to induce this phenomenon. Stopped-flow experiments revealed that PMBN and PMB induced the fusion of small unilamellar PS and large unilamellar DPPA-DSPC vesicles. The aggregation of vesicles was found to be diffusion-controlled process; the subsequent fusion took place with a frequency of 10(2)-(5 X 10(2] s-1 for small vesicles and 1-100 s-1 for large vesicles. The freeze-fracture replicas of the PMB-treated vesicles displayed 12-50-nm depressions on several superimposed bilayers, indicating the formation of stable lipid-PMB domains. Since the incubation with PMBN produced similar depressions only if the specimens were fixed, PMBN-induced domain formation seems to be a reversible rapid process. The differences in the phospholipid-peptide interactions are correlated with the differences in the physiological action of the antibiotic PMB and the nonbactericidal PMBN on the cell envelope of Gram-negative bacteria.

Calorimetry, Differential Scanning↗
PubMed1987

An enzyme-immunoassay for antibodies against hepatitis B core antigen: characteristics and clinical validation.

An enzyme-immunoassay (EIA) for antibodies to hepatitis B core antigen (anti-HBc) was developed. The new test uses undiluted samples, incubated directly into an HBcAg coated well. Three alternative test procedures are possible. The stability of reagents was studied and a preclinical evaluation was performed intramurally. An assay correlation study was organised. We report the results of the external evaluation performed at 4 centres. A mean analytical sensitivity of 1.1, 1.2 and 0.36 PEI units/ml anti-HBc was found for procedure I (1 h/1 h/30 min), procedure II (30 min/30 min/30 min) and procedure III (16-20 h/1 h/30 min), respectively. In total, 5288 determinations on serum or plasma from various patients and healthy individuals were performed: 10% with procedure I, 52% with procedure II and 38% with procedure III. The qualitative (positive or negative) results were compared with those found with tests used routinely at the centres--47% with Corzyme (Abbott) and 53% with Corab (Abbott)--in a first screening. A final evaluation was made taking into account the repeatability of the results. Based on all results together, the agreement between the new EIA for anti-HBc and the routine tests was 97.6% at the first screening and increased to 99.0% after further evaluation.

Blood Donors↗
PubMed1986

[Status of immunity against poliomyelitis in Germany].

Neutralizing antibodies against poliovirus types 1, 2 and 3 were determined in serum of 4,039 persons of different ages and of 879 persons at the beginning of their training (male recruits at their initial examination; female teaching trainees and student nurses). The sera were supplied by eleven institutions. Compared with similar studies in 1969, 1972 and 1978, the immunity against individual poliovirus types as well as that against the three types in the different age groups has improved. About three quarters of those older than seven years have antibodies against types 1, 2 and 3. The present study, which for the first time used a more sensitive neutralization test, revealed that about 85% of probands had antibodies against all three types. The trivalent immunity of those aged from 0 to six years has improved by 11 percent points since 1978. There was no decrease in immunity among those older than 20 years.

Adolescent↗