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M Frey

Publications and source records attributed to M Frey.

At least 145 records · Page 8Linked to original sources
PubMed1994

Adenosylmethionine-dependent synthesis of the glycyl radical in pyruvate formate-lyase by abstraction of the glycine C-2 pro-S hydrogen atom. Studies of [2H]glycine-substituted enzyme and peptides homologous to the glycine 734 site.

The active form of pyruvate formate-lyase (PFL) from Escherichia coli contains a glycyl radical in position 734 of the polypeptide chain which is produced post-translationally by pyruvate formate-lyase-activating enzyme (PFL activase) using S-adenosylmethionine (AdoMet) and dihydroflavodoxin as co-substrates (Wagner, A.F. V., Frey, M., Neugebauer, F.A., Schäfer, W., and Knappe, J. (1992) Proc. Natl. Acad. Sci. U. S. A. 89, 996-1000). Studying radical synthesis with [2-2H]glycine-labeled PFL, we have now found stoichiometric incorporation of a 2H atom into the 5'-deoxyadenosine (dAdo) co-product via mass and NMR spectroscopic analyses. Furthermore, a series of peptides homologous to the Gly-734 site of PFL have been synthesized for analyzing recognition determinants of PFL activase. Peptides that proved active as substrates (monitored by [14C]dAdo formation from [14C]AdoMet) were also competitive inhibitors of PFL conversion to the radical form. In the sequence of the standard peptide Arg-Val-Ser-Gly-Tyr-Ala-Val, which corresponds to amino acid residues 731-737 of PFL, the Gly residue was replaceable by D-Ala (actually displaying enhanced efficiency), whereas a normal Ala totally abolished the interaction with PFL activase. Our results show that the radical in pyruvate formatelyase is produced by stereospecific abstraction of the pro-S hydrogen of glycine 734 by the 5'-dAdo radical generated in the active center of PFL activase. Gly-734 is probably located in a beta-turn segment of the protein.

Acetyltransferases↗
PubMed1994

Role of calcium in arteriosclerosis--experimental evaluation of antiarteriosclerotic potencies of Ca antagonists. Study Group for Calcium Antagonism.

Chemical microanalyses of conventional human coronary artery plaques (stages I-III [WHO]) revealed the correlation between progressive mural Ca overload up to excessive degrees, and the severity of plaque formation, whereas only small amounts of cholesterol were found, even in complicated lesions. The pathogenetic role of Ca was tested in three types of experimental arteriosclerosis and atheromatosis, using Ca antagonists (verapamil, nitrendipine, diltiazem) as research tools: 1) The Ca type, in vitamin D3 plus nicotine-treated rats; 2) the cholesterol type, in cholesterol-fed New Zealand rabbits; 3) mixed types, in SHRs and NaCl-fed Dahl-S rats. Types (1) and (3) were demonstrated to be governed by a progressive arterial Ca uptake that could be established already in early lesions. The increased mural Ca supply promoted cellular necroses, migration, and proliferation, as well as calcification and degradation of elastic fibers. Ca antagonists prevented the increased Ca incorporation into arterial walls and inhibited the development of experimental arterioscleroses of types (1) and (3). Ca antagonists did not protect coronary arteries of cholesterol-fed rabbits (type [2]) from occlusive cholesterol accumulation. The data suggest an important pathogenetic role of Ca and pronounced antiarteriosclerotic potencies of Ca antagonists in Ca-dominated types of experimental arteriosclerosis. The significance of the present results for pathophysiology and therapy of conventional human arteriosclerosis remains to be clarified.

Adult↗
PubMed1994

Role of calcium antagonists in progression of arteriosclerosis. Evidence from animal experiments and clinical experience. Part I. Preventive effects of calcium antagonists in animal experiments.

The quantitative predominance of free and total cholesterol over the amount of mural calcium is a most significant criterion of healthy human coronary arteries during the whole life span (0-90 years). However, this normal ratio increasingly changes as soon as arteriosclerotic alterations of the coronary walls set in. Accordingly, the mural calcium content steadily rises from fatty streaks over severe arteriosclerosis and, lastly, seems to reach a climax in plaques which caused lethal coronary infarction. Furthermore, the severe arteriosclerosis of human art. dorsalis pedis with gangrene (and amputation) is characterized by a tremendous calcium incorporation and absence of any mural cholesterol changes. Only in rare cases of human basilary plaques was a dangerous cholesterol incorporation in brain arterial wall found without significant elevation of serum cholesterol levels. The presented data indicate the existence of two different types of arteriosclerosis in one and the same patient and two basically different types of experimental coronary plaques according to their chemical composition, microscopic aspect and responsiveness to calcium antagonists: 1) the calcium type, developing in vitamin-D3-treated rats, and 2) the cholesterol type, represented by fatty coronary atheromata of cholesterol-fed rabbits. Coronary atheromata of cholesterol-fed New Zealand rabbits may be suitable models for coronary heart disease in rare cases of human familiar hypercholesterolemia. The formation of conventional human coronary artery plaques, however, essentially requires a progressive uptake of calcium, thereby representing a calcium dominated type of arteriosclerosis. Calcium antagonists specifically inhibit progredient mural calcium uptake in all experimental models of arteriosclerosis tested so far. However, neither in atheromatous arteries nor in afflicted organs (myocardium, liver, kidneys) of cholesterol-fed rabbits were we able to find any significant prevention of cholesterol accumulation by calcium antagonist.

Aging↗
PubMed1994

The radial forearm flap as a pedicled flap for resurfacing a scarred nose.

The radial forearm flap, applied as a free flap, has been shown to be very versatile, if covering a defect with a thin, flexible flap is of predominant importance. The advantage of this technique compensates for any disadvantages in the donor area. Under certain circumstances it is a better solution to design the radial forearm flap as a distant, vascular pedicled flap than to perform it as a free flap with microvascular anastomoses. In treatment of this patient we used a distally pedicled radial forearm flap to resurface a burned nose and to reconstruct the tip of the nose. In this case a scarred forehead prevented us from using an expanded forehead flap. The increased morbidity of a distant, pedicled flap was well accepted as the price for preventing additional scarring in the face, as would have occurred in the case of a free flap, through the exposure of vessels for the vascular anastomoses.

Adolescent↗
PubMed1994

Development of a new documentation system for facial movements as a basis for the international registry for neuromuscular reconstruction in the face.

None of the paresis scoring systems used satisfies an adequate description of all the details necessary to document the degree of facial paresis before and after any treatment. We developed a new documentation system considering all details of the history of the patient and of the treatment that could have any influence on the functional result. The third part of this "international registry for neuromuscular reconstruction in the face" concerns paralysis assessment, including quantitative measurements of the resting and moving face, besides qualitative parameters. A map of standardized static and dynamic points in the face was designed, and three-dimensional measurements of the movements of these facial points were performed with a VICON system in 16 healthy individuals. On the basis of the results, three real static points and representative dynamic points were selected as well as relations of these points most representative for the different facial movements. For data collection, a simple instrument (Frey's faciometer) was developed. A preliminary report is given on the clinical application of this new instrument.

Adult↗
PubMed1994

Experimental vasoprotection by calcium antagonists against calcium-mediated arteriosclerotic alterations.

According to chemical analyses, the development of conventional human coronary artery plaques from "fatty streaks" to "fibrous plaques" and "complicated lesions" is dominated by progressive mural calcium (Ca) incorporation. The atherogenic significance of Ca ions and arterial Ca overload was examined under the influence of nicotine, oxidatively modified low-density lipoproteins, spontaneous hypertension, and an elevated extracellular Ca concentration or vitamin D3. Experiments were carried out either in vitro on cultured medial cells of rats or in vivo on various types of experimental arteriosclerosis of rats. Suitable Ca antagonists (verapamil, diltiazem, nifedipine, or nitrendipine) prevented experimental Ca overload of arterial walls and transmembrane Ca uptake into cultured medial cells produced by risk factors. Thus they protected, in vivo and/or in vitro, against the atherogenic potential of Ca ions, i.e., migration, proliferation, matrix production and intracellular Ca overload of vascular smooth-muscle cells, as well as calcification of elastic fibers. The data indicate that various Ca-consuming processes demand a progressive uptake of Ca into arterial walls if Ca-dominated types of arteriosclerosis develop. Under experimental conditions, specific Ca antagonists inhibit Ca-mediated arteriosclerotic alterations by preventing progressive mural Ca incorporation.

Adult↗
PubMed1994

Role of calcium antagonists in progression of arteriosclerosis. Evidence from animal experiments and clinical experience. Part II. Clinical experience with preventive effects of calcium channel blockers in atheromatous coronary artery disease.

Experimental evidence for antiatheromatous of effects of calcium antagonists has been impressive. Clinical experience has, in contrast, been more difficult to obtain. Primary prevention with calcium antagonists has not been studied due to obvious difficulties. Secondary prevention, however, has been investigated: Several studies have addressed influence of calcium antagonists upon atheromatous arterial wall changes as demonstrated by quantitative coronary angiocardiography. A review of these studies reveals considerable methodological problems. For nifedipine it could be demonstrated, however, that the occurrence of "new lesions" can be retarded to a certain extent (3-6). Nicardipine has been studied, but the preventive effect reported cannot be considered valid, because distribution of risk factors to the study groups was not statistically homogeneous. Another approach has been the application of calcium antagonists to patients with acute myocardial infarction. Here, vascular and myocardial effects come into play. In non-Q-wave, i.e. not transmural infarction, the calcium antagonist diltiazem definitely has preventive effects as regards re-infarction (2). The large multicenter post-myocardial infarction trial MDPIT showed an improvement of cardiac envent rate and re-infarction. This effect was seen only if pulmonary congestion was not present. Calcium antagonists have negative effects if cardiac failure is present. Verapamil was shown to have beneficial effects in acute myocardial infarction in the large DAVIT trials. Here again, the effect was only seen if heart failure was not present. Otherwise negative results were recorded. Nifedipine demonstrated only borderline myocardial protective effects in acute myocardial infarction (7). We conclude that calcium antagonists have vascular and myocardial protective effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Channel Blockers↗
PubMed1993

Fiber regeneration in nerve grafts without connection to a target muscle: an experimental study in rabbits.

In 30 rabbits, both saphenous nerves were harvested as autografts and coapted to the branch for the rectus femoris muscle without connection to any distal target muscle. The graft from the right thigh was led to the contralateral extremity (crossover grafting). The graft on the left side remained on the same extremity (ipsilateral grafting). Animals were separated into four groups and were sacrificed 3, 6, 9, and 12 months after grafting. Specimens of the grafts and the donor motor branches were harvested for histomorphometric examination. The number of myelinated nerve fibers in the distal end of the nerve grafts was significantly increasing from 3 to 6 months after grafting and remained on a relatively constant level in the long-term groups. Three months after the first operation, greater numbers of myelinated nerve fibers were counted after ipsilateral grafting than after crossover grafting. In the long-term groups, this difference could not be observed.

Animals↗
PubMed1993

Definition and characterization of an artificial En/Spm-based transposon tagging system in transgenic tobacco.

A transposon tagging system for heterologous hosts, based on the maize En/Spm transposable element, was developed in transgenic tobacco. In this system, the two En-encoded trans-acting factors necessary for excision are expressed by fusing their cDNAs to the CaMV 35S promoter. The dSpm receptor component is inserted in the 5'-untranslated leader of the bar gene. Germinal revertants can therefore be selected by seed germination on L-PPT-containing medium or by spraying seedlings with the herbicide Basta. Using this bar-based excision reporter construct, an average frequency of germinal excision of 10.1% was estimated for dSpm-S, an En/Spm native internal deletion derivative. Insertion of En-foreign sequences in a receptor, such as a DHFR selectable marker gene in dSpm-DHFR, does not abolish its capacity to transpose. However, dSpm-DHFR has a lower frequency of somatic and germinal excision than dSpm-S. Revertants carrying a transposed dSpm-DHFR element can be selected with methotrexate. Germinal excision is frequently associated with reinsertion but, as in maize, dSpm has a tendency to integrate at chromosomal locations linked to the donor site. Concerning the timing of excision, independent germinal transpositions are often found within a single seed capsule. All activity parameters analysed suggest that transposon tagging with this system in heterologous hosts should be feasible.

Base Sequence↗
PubMed1993

[Relations between donor nerve size and degree of neurotization in the nerve transplant--an experimental study].

The present study was undertaken to investigate whether the number of myelinated fibers in a sensory nerve used as an autograft influences the result of nerve fiber regeneration in the graft. In 30 rabbits, the left saphenous nerve was used as an autograft. It was coapted to the motor branch to the rectus femoris muscle. Biopsies from both ends of the graft were taken. Animals were separated into four investigation groups, which were reexamined 3, 6, 9 and 12 months after the grafting procedure. Biopsies for histological and morphometric examination were again taken from the proximal and the distal part of the grafts. Thus, the number of myelinated nerve fibers in the different specimens could be obtained by computer-assisted image analysis. At the proximal end of the original saphenous nerve, the number of fibers varied between 1032 and 3100 (mean 2145). Corresponding data obtained from the distal end ranged from 1044 to 3084 myelinated nerve fibers (mean 1724). Fiber numbers in the proximal and distal parts of the grafts before and after regeneration were correlated to each other. In the whole population of specimens (correlation coefficient +/-0) as well as in the experimental subgroups, the quantitative success of neurotization in the grafts did not depend to a high degree upon the fiber numbers in the original saphenous nerve. The correlation coefficient for the proximal part of the graft exceeded 0.5 to only three and twelve months after grafting, but did not reach a level of statistical significance. In the distal part of the graft, the coefficient for a linear correlation was always less than 0.45.

Animals↗
PubMed1993

Mobility of the maize transposable element En/Spm in Arabidopsis thaliana.

The autonomous element En-1 of the maize En/Spm transposable element system is capable of frequent somatic and germinal excision in the heterologous host Arabidopsis thaliana. The pattern of En-homologous transcripts generated in transgenic Arabidopsis resembles En transcription in maize. An excision reporter construct based on NPT-II gene (pKEn2) can be used reliably for the isolation of En-1 germinal revertants by seed germination on kanamycin-containing medium. Re-insertion after germinal excision is apparently frequent. A dSpm receptor element can be efficiently trans-activated in Arabidopsis either by En-1 or by expressing cDNAs of tnpA and tnpD. Excision and re-insertion of En/Spm take place with similar characteristics as in maize. This is the first description of En/Spm transposition in Arabidopsis and the parameters analysed here suggest that transposon tagging with En should be feasible in this species.

Arabidopsis↗
PubMed1992

The free radical in pyruvate formate-lyase is located on glycine-734.

Pyruvate formate-lyase (acetyl-CoA:formate C-acetyltransferase, EC 2.3.1.54) from anaerobic Escherichia coli cells converts pyruvate to acetyl-CoA and formate by a unique homolytic mechanism that involves a free radical harbored in the protein structure. By EPR spectroscopy of selectively 13C-labeled enzyme, the radical (g = 2.0037) has been assigned to carbon-2 of a glycine residue. Estimated hyperfine coupling constants to the central 13C nucleus (A parallel = 4.9 mT and A perpendicular = 0.1 mT) and to 13C nuclei in alpha and beta positions agree with literature data for glycine radical models. N-coupling was verified through uniform 15N-labeling. The large 1H hyperfine splitting (1.5 mT) dominating the EPR spectrum was assigned to the alpha proton, which in the enzyme radical is readily solvent-exchangeable. Oxygen destruction of the radical produced two unique fragments (82 and 3 kDa) of the constituent polypeptide chain. The N-terminal block on the small fragment was identified by mass spectrometry as an oxalyl residue that derives from Gly-734, thus assigning the primary structural glycyl radical position. The carbon-centered radical is probably resonance-stabilized through the adjacent carboxamide groups in the polypeptide main chain and could be comparable energetically with other known protein radicals carrying the unpaired electron in tyrosine or tryptophan residues.

Acetyltransferases↗
PubMed1992

[2-Amino-3-cyano-dihydroindol-5-ones. 3. The chemical reactivity of a new class of compounds].

The chemical reactivity of cytotoxic 5-indolone derivatives is examined in order to get ideas about their behaviour in biological systems. Dienone-phenol-rearrangement preserving the indole ring system could not be achieved, aromatization of 1b gives the phenol derivative 3 alpha. In diluted NaOH ester hydrolysis occurs (1a,b----4a,b). Hydrolysis in conc. H2SO4 yields the amides 5a,b,d. In ethanolic HCl the ammonium salts 6a,b,d are formed. Acylation of 1a to 8 reveals the endocyclic N-atom as the nucleophilic center. Benzaldehyde being a strong electrophile adds to 1b in position 4. Weaker electrophiles such as dimethyl acetylenedicarboxylate (ADC) only react with the amides 5b,d to give 11 and 12. Nucleophiles (water, ethanol, n-propylamine) add to the delta 6-double bond yielding 14-16.

Antineoplastic Agents↗