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Biomedical subjects

F Müller

Publications and source records attributed to F Müller.

At least 451 records · Page 25Linked to original sources
PubMed1982

A study of p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens: chemical modification of histidine residues.

The flavoprotein p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens is inactivated by diethyl pyrocarbonate. Below pH 7, diethyl pyrocarbonate reacts specifically with histidine residues. The inactivation reaction is biphasic and follows pseudo-first-order kinetics. Four of the nine histidine residues of the enzyme are modified. During the first phase of the reaction, one histidine residue is modified and leads to a loss of about 30% of the activity. Modification of the additional three histidine residues during the second phase leads to complete loss of activity. Two of the latter histidine residues are essential for activity and are involved in the binding of reduced nicotinamide adenine dinucleotide phosphate (NADPH). The activity can be restored almost quantitatively upon treatment of modified enzyme with hydroxylamine. The modified enzyme is still capable of binding NADPH. The dissociation constant of the enzyme-NADPH complex is larger by a factor of 10 for the modified enzyme as compared to that for the native enzyme. The modification does not affect the affinity of the enzyme for the substrate, although effectors protect two histidine residues from chemical modification by diethyl pyrocarbonate. The rate of inactivation of the enzyme is pH dependent and increases with increasing pH values. From the pH dependence of the rate constant, it is calculated that two cooperative histidine residues participate in the reaction with diethyl pyrocarbonate. Both histidine residues possess a pKa' value of 6.2. At pH greater than 7, other reactions take place which are completely abolished in the presence of an effector (substrate) of the enzyme.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1982

On the enigma of old yellow enzyme's spectral properties.

Old yellow enzyme (NADPH oxidoreductase) in the free and complexed state was thoroughly investigated by the following techniques: absorption, circular dichroism, fluorescence/phosphorescence and electron paramagnetic resonance spectroscopy and fluorescence/phosphorescence decay measurements, applied over a wide range of temperature (7-293K). The data obtained were interpreted by comparison with results from similar measurements on free FMN, existing spectral data on isoalloxazine model systems and theoretical data. The results clearly demonstrate the inadequacy of a simple phenolate-FMN donor-acceptor charge-transfer complex to explain the phenomena occurring upon the addition of phenols to old yellow enzyme. Instead it was found that the phenolate anion interferes strongly with an existing tight complex between FMN and the apoprotein, probably an H-bonded structure in which FMN is tautomerized and interacts with an L-chiral center. This is concluded from a separate electronic transition with an origin at 496 nm, thus far not recognized as such, and the circular dichroism observed. The emission is dominated by that of free FMN, although protein-bound FMN seems also to become luminescent in glassy solution at 143 K. A second fluorescence/phosphorescence emission appears upon excitation of both native and complexed old yellow enzyme in the ultraviolet. This emission is quenched by the addition of phenol to the enzyme, shows a large (3000-cm-1) blue shift on going to a low-temperature glass and is tentatively assigned to excimers of nucleic acids. Long-wavelength excitation with a synchronously pumped, mode-locked Rhodamine 6-G dye laser revealed a third, extremely weak emission in both native old yellow enzyme and its complexes. It decays with a lifetime of about 3 ns at 143 K. Electron paramagnetic resonance spectra revealed the presence of a low amount of an unpaired spin in old yellow enzyme. Owing to an unusual relaxational behaviour it could only be observed below 15 K and, again, the signal was measured in both the native enzyme and its complexes. Possible assignment and consequences of this observation are discussed. In frozen aqueous solutions of the enzyme-phenolate complex, a phase transition was discovered at which the colour of the complex reverted to that of the native enzyme. Subsequent melting restored the original colour. The observed phenomena and existing literature data lead to the conclusion that the only model from which no apparent inconsistencies emerge is that of a very complicated network of hydrogen-bonded structures in the protein. These involve several, partly unknown, chromophores. Phenols interfere with this network, leading to the formation of the long-wavelength absorption band in old yellow enzyme.

Chemical Phenomena↗
PubMed1982

Nucleotide sequence of satellite DNA contained in the eliminated genome of Ascaris lumbricoides.

Several restriction endonuclease fragments isolated from highly repetitive satellite DNA of the chromatin eliminating nematode Ascaris lumbricoides var. suum have been cloned. Each type of restriction fragment corresponds to a different variant of the same related ancestral sequence. These variants differ by small deletions, insertions and single base substitutions. Restriction and DBM blot analyses show that members of the same variant class are tandemly linked and therefore are physically separated from other variant classes. A comparison of all the determined sequences establishes a 121 bp long and AT rich consensus sequence. There is evidence for an internal short range periodicity of 11 bp length, indicating that the Ascaris satellite initially may have evolved from an ancestral undecamer sequence. The satellite DNA sequences are mostly but not entirely eliminated from the presumptive somatic cells during chromatin diminution. We have no evidence for transcriptional activity of satellite DNA at any stage or tissue analyzed.

Animals↗
PubMed1982

A photo-CIDNP study of the active sites of Megasphaera elsdenii and Clostridium MP flavodoxins.

Megasphaera elsdenii and Clostridium MP flavodoxins have been investigated by photo-CIDNP techniques. Using time-resolved spectroscopy and external dyes carrying different charges it was possible to assign unambiguously the resonance lines in the NMR-spectra to tyrosine, tryptophan and methionine residues in the two proteins. The results show that Trp-91 in M.elsdenii and Trp-90 in Cl.MP flavodoxin are strongly immobilized and placed directly above the benzene subnucleus of the prosthetic group. The data further indicate that the active sites of the two flavodoxins are extremely similar.

Binding Sites↗
PubMed1982

[Specificity and sensitivity of immunological diagnosis of congenital neonatal syphilis by the 19S(IgM)-FTA-ABS test (author's transl)].

Reports on the significance in the demonstration of IgM class antibodies in congenital syphilis are contradictory. The reason for discrepant observations are of technical or biological source. In order to explain the several uncertainties, serum samples from 1031 newborns and infants of syphilitic mothers were investigated quantitatively with the IgM-FTA-ABS, the 19S (IgM)-FTA-ABS and cardiolipin CF test. If serum specimens of the mothers were available they were investigated in the same tests for treponema-specific 19S(IgM) class and antilipoidal antibodies. In the evaluation of the results, the history of infection and treatment of the mothers as well as clinical observations in the infants were considered. In 26 children a congenital acquired syphilis was strongly indicated by demonstration of treponema-specific 19S(IgM) class antibodies by the 19S(IgM)-FTA-ABS-Test and tae good agreement with the history of untreated mothers. In another 1005 infants a congenital infection by T. pallidum could be excluded by the non-reactive 19S(IgM)-FTA-ABS as well as clinical observations. Furthermore, immunological findings of three children who had acquired syphilis after birth are demonstrated before and after specific treatment. It could be shown that the 19S(IgM)-FTA-ABS is much more infaillable than the IgM-FTA-ABS as far as technical and biological uncertainties are concerned. Considering all possible errors and the results of re-investigations of IgM non-reactive infants of syphilitic mothers (up to one year after birth) it is demonstrated that congenital syphilis can be differentiated from passively transmitted 7S(IgG) class antibodies (of the mother) or 19S(IgM) class anti-antibodies (of the child) with a significance of about 99%. It is finally concluded that serological diagnosis of congenital syphilis should be started in the pregnant women. By making the diagnosis in pregnancy followed by adequate treatment, irreversible damages as well as so-called serological scars can be avoided in the children.

Antibodies, Bacterial↗
PubMed1982

Structural and dynamic information on the complex of Megasphaera elsdenii apoflavodoxin and riboflavin 5'-phosphate. A phosphorus-31 nuclear magnetic resonance study.

It is shown that commercial FMN contains a considerable amount of the 4', 3', and 2' isomers and other phosphorus-containing compounds. These impurities can easily be analyzed and quantified by the 31P NMR technique. The phosphate group of FMN bound to Megasphaera elsdenii apoflavodoxin is probably in the dianionic form. Its chemical shift is almost independent of pH in the range 5.5-9.2 and of the redox state of the protein. The phosphate group of bound FMN is buried in the protein. Protons of the apoprotein and of bound water located in the vicinity of the phosphate group in native flavodoxin are not exchangeable with deuteron of the bulk solvent. These protons are, however, easily exchangeable in apoflavodoxin, as shown by reconstitution experiments. The distance between the phosphorus atom of bound FMN and the N(10) atom of the isoalloxazine moiety of FMN is calculated to be about 7.8 A. This result is in good agreement with X-ray data published for the related flavodoxin from Clostridium MP. The electron exchange between the oxidized and semiquinone state of M. elsdenii flavodoxin is rather slow (kexc' much less than 2 s-1) whereas that between the semiquinone and hydroquinone form is much more favored (kexc' much greater than 100 s-1). This indicates that the activation energy for the transition between the semiquinone and hydroquinone states must be smaller than that for the transition between the oxidized and semiquinone states. These results offer a reasonable explanation for the one-electron transfer reaction of flavodoxins in biological reactions.

Apoproteins↗
PubMed1982

Situational reactivity of autonomic functions in schizophrenic patients.

In a study designed to evaluate the state of arousal and the autonomic reactivity to experimental conditions in schizophrenic patients, 12 acute, unmedicated schizophrenic patients with paranoid hallucinatory symptomatology and 63 healthy normal control subjects were administered four standardized tasks: cold pressor test, noise, mental arithmetic, and active relaxation. Biochemical (norepinephrine and cortisol) and physiological (electromyogram, electroencephalogram, skin and conductance response, skin conductance level, finger pulse amplitude, finger temperature, heart rate, respiratory volume, pulse wave velocity, and electrogastrogram) parameters were measured simultaneously. Schizophrenic patients showed elevated levels of cortisol and norepinephrine, as well as heightened responsivity on measures of electromyographic activity, skin conductance level, and heart rate, throughout the trial, and reduced responsivity to conditions of stress. It is concluded that schizophrenic patients show higher nonspecific activation and reduced ability to react to external stimulation, perhaps induced by lack of inhibition of the reticular formation by the limbic system.

Acute Disease↗
PubMed1982

Demonstration of specific 19S(IgM) antibodies in untreated and treated syphilis. Comparative studies of the 19S(IgM)-FTA test, the 19S(IgM)-TPHA test, and the solid phase haemadsorption assay.

Sera from 408 patients with untreated or treated syphilis were examined by three different tests to demonstrate treponema-specific 19S(IgM) antibodies. Antibody titers in the 19S(IgM)-fluorescent treponemal antibody (FTA) test and the solid phase haemadsorption assay (SPHA) did not correlate. The 19S(IGM)-Treponema pallidum haemagglutination assay (TPHA) and the SPHA partly correlated based on the concentration of treponema-specific 19S(IgM) antibodies in the patient's serum. Under experimental conditions antibody titres in the 19S(IGM)-FTA test and the 19S(IgM)-TPHA correlated consistently. For specificity and sensitivity, the 19S(IgM)-FTA test correlated best with the clinical findings in both untreated and successfully treated patients. Although the 19S(IgM)-TPHA has about the same degree of specificity, the reading of the results is technically more complicated. The specificity of the SPHA was very high. In patients with untreated syphilis, however, the SPHA is adversely affected by a high rate of false non-reactive results, since it consists of two reactions with appreciable differences in sensitivity. Thus, higher sensitivity cannot be expected in the SPHA. An immunoadsorption technique using an adequate antigen and a specific, enzyme-labelled antiserum might provide an alternative test which is simple to perform, highly specific, and consistently sensitive.

Antibodies, Bacterial↗
PubMed1982

Experimental stress situations and the state of autonomic arousal in schizophrenic and depressive patients.

The influence of short-time emotional and cognitive stimuli on autonomic functions and plasma catecholamines was investigated in 12 paranoid schizophrenics, 12 endogenous depressive patients, and 63 normal controls. The schizophrenics showed higher norepinephrine levels, depressives higher epinephrine levels; in both groups of patients most of the physiological parameters were elevated throughout the trial, showing, on the other hand, reduced responsiveness to external stimulation.

Adult↗
PubMed1982

Personality, coronary-prone behaviour and adrenergic factors in essential hypertension: possible implications for cardiac prevention.

An association between high blood pressure and the coronary-prone (or type A) behaviour pattern, established as risk factors for myocardial infarction and sudden death, has been postulated on the basis of similar psychophysiological mechanisms involving the sympathetic nervous system. Psychodynamic personality profiles and type A behaviour assessment have therefore been related to biochemical markers of sympathetic overactivity, but type A behaviour scores were generally found to be low in hypertensive subjects - and lowest in those with high plasma noradrenaline. However, projective assessment of reactions to frustration during everyday stress indicates that hypertensive patients with high plasma renin activity as well as high noradrenaline have less externalized but more internalized aggression, and are submissive yet have a stronger need to resolve conflicts immediately. These incompatible tendencies result in chronic frustration. A similar high degree of suppressed anger is shared by patients at risk for coronary heart disease, and high renin patients have a higher incidence of critical cardiac events. This suggests the possibility of a 'hypertensive coronary-prone personality'. Because of their excellent antihypertensive response to chronic beta-blocker therapy, it is conceivable that high renin patients benefit most from the cardioprotective potential of beta-blocker-based antihypertensive therapy.

Adrenergic beta-Antagonists↗
PubMed1982

[Detection of a Na+-activated, furosemide-inhibited ATPase activity in rat intestinal mucosa].

An ouabain-insensitive, Mg++-dependent, Na+-stimulated ATPase activity which is inhibited by furosemide was found in mucosal homogenate of rat small intestine. The subcellular localization of this ATPase activity was studied by means of isolated purified brush borders and basolateral plasma membranes. The results suggest a nearly identical distribution of Na+-activated and (Na+K+)-activated ATPase within the epithelial cells. Under conditions of alloxan and streptozotocin diabetes an increase of both ATPase activities can be found only in the basolateral plasma membranes. These observations agree well with the convective model of intestinal absorption.

Adenosine Triphosphatases↗
PubMed1982

Molecular cloning and sequence analysis of highly repetitive DNA sequences contained in the eliminated genome of Ascaris lumbricoides.

High molecular weight DNA from germ line and somatic cells of the DNA eliminating nematode Ascaris lumbricoides has has been isolated and digested with different restriction enzymes. The resulting DNA fragments were separated by agarose gel electrophoresis. Germ line but not somatic DNA shows a prominent band about 120 bp long as well as multiples of that length. These fragments are shown to be monomers and multimers of a highly repetitive satellite DNA, which is eliminated mostly but not completely during the process of chromatin diminution. Restriction digests, hybridization experiments and sequence analysis revealed that this eliminated satellite is composed of a whole set of different but related variant classes, all of them showing the same repeating unit length of about 120 bp. Members of the same variant class are tandemly linked and therefore physically separated from other variant classes. All satellite sequences can be derived from the same common ancestor sequence, differing only by base substitutions, insertions and deletions. There is no evidence for transcription of satellite DNA at any stage and tissues analyzed.

Animals↗
PubMed1982

[Increase of (Na+ + K+)-activated ATPase activity of basolateral plasma membranes from intestinal mucosa of diabetic rats].

A significant increase of the (Na+ + K+)-activated ATPase was found in mucosal homogenates of rat small intestine under conditions of alloxan and streptozotocin diabetes. From studies with isolated plasma membranes it has been shown that the activity changes were caused by that part of the (Na+ + K+)-activated ATPase only which is localized in the basolateral plasma membranes, whereas the enzyme activity in the brush border region remains unchanged. In connection with the enhanced capacity of ion, nonelectrolyte and water absorption in experimental diabetes, our findings support a concept of intestinal transport mechanism which suggest that the basolateral part of the (Na+ + K+)-activated ATPase is responsible for metabolic energy supply. The luminal part of the enzyme may be involved in regulation of passive Na+ influx.

Animals↗
PubMed1982

[The 19S(IgM)-FTA-ABS test in the serodiagnosis of syphilis. Technique, sources of error and diagnostical information of results (author's transl)].

This study is based on the results of investigations with the 19S(IgM)-FTA-ABS in serum samples of more than 10,000 patients with treated or untreated syphilis. On the basis of the findings several experiences concerning the technique of the test as well as the possibilities of biological or technical errors are reported. Furthermore, the interpretation of test results is discussed. It is shown that in many cases a differentiation between sufficiently treated and those patients is possible who need specific treatment. Finally the indications for preparing the test are mentioned. It is concluded that at the present time the performance of the 19S(IgM)-FTA-ABS test should be restricted to specialized laboratories.

Antibody Formation↗