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Biomedical subjects

G Maass

Publications and source records attributed to G Maass.

At least 109 records · Page 6Linked to original sources
PubMed1981

Transient cleavage kinetics of the Eco RI restriction endonuclease measured in a pulsed quench-flow apparatus: enzyme concentration-dependent activity change.

We report measurements of the cleavage rate of pBR 322 plasmid DNA by the restriction endonuclease Eco RI as a function of enzyme and DNA concentration. The reaction, which at high excess of enzyme over DNA occurs between 0.2 and 5 seconds, was studied by the means of a microprocessor controlled pulsed quench-flow apparatus. Enzyme concentrations were between 1 and 100 nM with DNA concentrations being 3 to 6 nM (specific Eco RI sites). The catalytic constants for cleavage of the first and second phosphodiester bonds as measured at high enzyme concentration both have the same value of 0.35 sec-1 and 21 degrees C. At enzyme concentrations comparable to or less than DNA concentration, the rate of the first cleavage is proportional to enzyme concentration, while the second step is independent of concentration. At approx. 10 nM Eco RI endonuclease concentration, a rate increase shows up in both the first and the second cleavage. We suggest that this increase is due to the tetramerization reported by Modrich & Zabel1, which occurs in this concentration range.

DNA Restriction Enzymes↗
PubMed1981

[The problem patient in dermatological practice. Psychomatic aspects (author's transl)].

In an exemplary case (44 year old female patient with pruritus) the priority of somatic aspects of an "organized disease" is questioned. The conception of a "total diagnosis" on the basis of a "pluriperspective complementary medicine" taking into consideration genetic, anatomic, physiologic, biochemical, microbiological, psychological and sociocultural facts is presented as the antithesis. Besides a somatic diagnosis the aim of medical procedure is the recognition ("reference diagnosis") of a "reference disturbance" in the doctor-patient relationship in which the "fundamental disturbance" of the patient is recalled from early childhood. This reference diagnosis can be learned by dermatologists and general practitioners in Balint groups.

Adult↗
PubMed1980

Inhibition of Eco RI action by polynucleotides. A characterization of the non-specific binding of the enzyme to DNA.

The cleavage of the plasmid pBR322 by the restriction endonuclease Eco RI has been studied in the presence of various polynucleotides and the double stranded octanucleotide d-(GGAATTCC) in order to clarify whether there is a preferential interaction of Eco RI with DNA sequences other than -GAATTC-. The steady state kinetic analysis shows that all polynucleotides investigated with the possible exception of poly-dG.poly-dC inhibit the cleavage competitively with Ki values in the range of 10(-4) to 10(-5) [M nucleotides]. The Ki of d-(GGAATTCC) is 1.5.10(-6) [M nucleotides], indicating that the specific binding is approx. 2 orders of magnitude stronger than non-specific binding.

DNA Restriction Enzymes↗
PubMed1980

[Antibodies to rotavirus in human milk (author's transl)].

116 human milk specimens taken from 36 women during the first 10 days after delivery were investigated for antibodies against rotavirus by crossimmunoelectrophoresis. Antibodies were detected in 37 specimens from 24 women, the antibody titers proved to be lower than the serum antibody titers. Antibody concentrations in the colostral and transitory milk samples declined continuously during the 10 days after delivery. Women with high serum antibody titers against rotavirus possessed antibodies in their colostrum more frequently than women with low antibody titers. There was no difference between the antibody titers in the sera of the women and the corresponding cord blood.

Antibodies, Viral↗
PubMed1979

Conformation transitions of a tRNA--aminoacyl-tRNA synthetase complex induced by tRNAs bearing different modifications in the 3' terminus.

The influence of modifications of the 3'-terminal adenosine of tRNAPhe (yeast) on the complex formation between this tRNA and phenylalanyl-tRNA synthetase (yeast) has been investigated by using fluorescence titrations and fast kinetic techniques. Subtle changes in the 3' terminus are reflected by distinct alterations in the two-step recognition process which had been demonstrated earlier for the native substrate tRNAPheCCA [Krauss, G., Riesner, D., & Maass, G. (1977) Nucleic Acids Res. 4, 2253--2262]. Binding experiments with tRNAPheCC, tRNAPheCCA-ox-red, tRNAPheCC2'dA, tRNAPheCC3'dA, tRNAPheCC-formycin, and tRNAPheCC-formycin-ox-red confirm that the 3'-terminal adenosine participates in a conformational change of the tRNA--synthetase complex. This is valid in both the absence and presence of phenylalaninyl-5'-AMP, the alkyl analogue of the aminoacyladenylate. As compared to tRNAPheCCA, a slower conformational change is observed with the competitive inhibitor tRNAPheCC-formycin-ox-red. The reaction enthalpy and/or the quench of the Y-base fluorescence that accompany the conformational change are altered upon binding of tRNAPheC2'dA, tRNAPheCC3'dA, and tRNAPheCC-formycin. It is evident that the final adaptation between tRNA and its synthetase in the complex is determined by the chemical nature of the 3'-terminal nucleotide. This is of vital importance for the specificity of the aminoacylation process.

Amino Acyl-tRNA Synthetases↗
PubMed1979

[Immunity against poliomyelitis in the German Federal Republic (author's transl)].

The immunity of the populations of several countries of the GFR against poliovirus 1, 2 and 3 was investigated in 11 laboratories. Sera of 4707 persons aged 0 to 30 years were assessed for neutralising antibodies (serum dilution 1:4) against the 3 types of poliovirus. 34.5% of the 4707 investigated sera had no neutralising antibodies at least against one type of the poliovirus, 4.7% showed no antibodies against all 3 types of the virus. Especially children aged 0 to 4 years were protected incompletely against the 3 types of poliovirus. In comparison with similar investigations of 1969 and 1972 no decisive change of immunity of the population of the GFR against poliomyelitis has occurred.

Adolescent↗
PubMed1979

The binding of tyrosinyl-5'-AMP to tyrosyl-tRNA synthetase (E.coli).

The binding between tyrosyl-tRNA synthetase (E.coli) and the alkylanalogue of the aminoacyladenylate, tyrosinyl-5'-AMP, has been investigated by fluorescence titrations and rapid mixing experiments. Tyrosyl-tRNA synthetase has two equivalent and independent binding sites for tyrosinyl-5'-AMP. The intrinsic binding constant is 4 x 10(7)M-1. The binding sites for tRNATyr and tyrosinyl-5'-AMP are independent of each other, the anticooperative mode of tRNA binding being preserved in the presence of tyrosinyl-5-AMP.

Adenosine Monophosphate↗
PubMed1979

[Risk of transmission of hepatitis B through contact lens fitting set].

8 out of 19 cases of acute or chronic hepatitis, with positive hepatitis B surface antigen (HBsAg) had HBsAg-positive tears. In 25 healthy HBsAg carriers, no HBsAg was found in the tears. The HBsAg concentration in the tears of hepatitis patients was less than 1% of the HBsAg in their blood. Contact lenses (soft hydrophilic, silicone) experimentally contaminated with HBsAg were practically free of it after the usual cleaning and washing with a commercial contact lens cleaning fluid. No adsorption of HBsAg was found on hydrophilic soft lenses; a minimal adsorption on silicone lenses could not be entirely excluded, but practically it was without any importance. In 14 samples of 79 storage fluids of a contact lens fitting set HBsAg was found. The cause of this contamination is not clear.

Acute Disease↗
PubMed1979

[Rotavirus infections in children (author's transl)].

In 43 out of 90 children suffering from acute gastroenteritis Rotaviruses could be identified in stool-specimens by electronmicroscopy. Symptoms were watery diarrhoea (100%), vomiting (88%), fever (77%), dehydration (47%) and upper respiratory tract infection (21%). In 3 out of 9 patients liver involvement could be documented. In 29 children i.v.-fluid therapy for 1-2 days was necessary. Only in 1 patient severe diarrhoea persisted for 11 days.

Acute Disease↗
PubMed1978

Open chain crown-type polyethers and pyridinophane cryptands act as ionophores upon frog motor nerve and isolated rat heart cells.

Frog motor nerves and isolated heart cells from neonatal rats were incubated with solutions of open chain crown-type polyether or pyridinophane cryptand. The following alterations in membrane excitability and energy consumption were found: 1. The non-cyclic ligand stabilizes the resting potential of the frog nerve and reduces the pulsation rate of heart muscle cells. It is reversibly bound at the cell surface and does not affect the energy metabolism of the heart cells. (formula: see text) 2. The cryptand 1,12-dioxo-2,11-diaza-5,8,21,24-tetraoxa[12-8(2,11)] (2,6)-pyridinophane) ([2.2.1py]-diamide) is irreversibly bound by the tissues. It facilitates the depolarization of the nerve and shows a positively chronotropic effect upon the heart muscle cells. Single treatment of the cell cultures with 10 microgram [2.2.1py]-diamide per ml medium increased the activities of lactate dehydrogenase and of creatine kinase. When the cell cultures were treated three times at 24 h intervals with 10 microgram complexone/ml, the creatine kinase activity of the heart muscle cells decreased by about 40%. The physiological properties of the ligands are correlated with the stability of their alkali metal ion complexes and with the rate constants of complex formation. It is concluded that [2.2.1py]-diamide can act as a passive carrier for Na+ K+.

Animals↗
PubMed1978

Diarrhea in newborn cynomologus monkeys infected with human rotavirus.

Of six newborn cynomolgus monkeys (Macaca fascicularis) naturally delivered and normally nursed five developed diarrhea after oral administration of human rotavirus. Virus excretion was observed in the stool of four animals. This virus was transmitted to four out of six other monkeys causing diarrhea in only one animal.

Animals↗
PubMed1978

A novel conformational change of the anticodon region of tRNAPhe (yeast).

The temperature dependence of the fluorescence of the Y-base of tRNAPhe (yeast) was investigated kinetically by the temperature jump method. In the range between -15 degrees C and +30 degrees C A NOVEL CONFORMATIONAL TRANSITION OF THE TRNA could be characterized. This conformational change was found in the absence of any artificial label; it is a characteristic property of tRNAPhe in its native structure. This transition accounts for 30% of the total fluorescence change. Its activation enthalpy is 16 kcal/mole (67 kJ/mole), and the transition enthalpy is between -2 kcal/mole and +2 kcal/mole (+/-8 kJ/mole). A model is represented in which this transition can be explained by a a change in the stacking pattern of the anticodon loop. The experimental findings are discussed with respect to several hypotheses about the molecular mechanism of protein biosynthesis which postulate conformational rearrangements of the anticodon loop.

Anticodon↗
PubMed1978

The binding of kirromycin to elongation factor Tu. Structural alterations are responsible for the inhibitory action.

The influence of kirromycin on the elongation factor Tu (EF-Tu) in its binary and ternary complexes was investigated. The equilibrium constant for the binding of the antibiotic to EF-Tu . GDP and EF-Tu . GTP was determined by circular dichroism titrations to be 4 x 10(6) M-1, and to EF-Tu . GTP . aa-tRNA by a combination of circular dichroism titrations and hydrolysis protection experiments to be 2 x 10(6) M-1. In the presence of kirromycin the binding of aminoacyl-tRNAs to EF-Tu . GTP is weakened by a factor of two. The antibiotic changes the conformation of the ternary complex in such a way that the aminoacyl moiety of the aminoacyl-tRNA is more accessible to the non-enzymatic hydrolysis. It is concluded that this structural alteration is responsible for the inhibitory action of the antibiotic.

Anti-Bacterial Agents↗