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Biomedical subjects

B Friedrich

Publications and source records attributed to B Friedrich.

At least 145 records · Page 8Linked to original sources
PubMed1981

Naturally occurring genetic transfer of hydrogen-oxidizing ability between strains of Alcaligenes eutrophus.

Mutants defective in chemolithoautotrophic growth (Aut-) have been isolated from Alcaligenes eutrophus strains H16, N9A, G27, and TF93. Spontaneous Aut- mutants were obtained only with strain TF93. Mutants of the other strains were selected after conventional mutagenesis or treatment with mitomycin. Most of the mutants, including the spontaneous Aut- strains, lacked hydrogenase activity (Hox-) but possessed the ability to fix carbon dioxide (Cfx+). Agar mating of A. eutrophus H16 with Hox- mutants of the various strains resulted in transconjugants which had recovered the ability to grow autotrophically and to express activity of hydrogenase as examined by enzymatic and immunochemical analysis. Transfer of hydrogen-oxidizing ability occurred in the absence of a mobilizing plasmid such as Rp4. The transfer frequency was particularly high (ca. 10(-2) per donor) when the spontaneous Hox- mutants of strain TF93 were used as recipients. These strains proved to be plasmid free, whereas donors, transconjugants, and the mutagen-treated Hox- mutants contained a large plasmid (molecular weight, 270 +/- 10 X 10(6) revealed by agarose gel electrophoresis. The results allow the conclusion that A. eutrophus H16 harbors a self-transmissible plasmid designated pHG1, which carries information for hydrogen-oxidizing ability.

Alcaligenes↗
PubMed1980

[Extracranial carotid stenosis and its sonographic diagnosis].

The direct Doppler examination of the carotid arteries as a method to detect and distinguish stenoses and occlusions of the common, internal, and external carotid arteries allows to decide on operability and indication for surgical treatment. The exact observation of the acoustical flow signals permits to a high degree an identification of even small stenoses and arteriosclerotic plaques. In 125 angiographical controls 95% of the sonographic diagnoses, in stenoses larger than 50% correct diagnosis could be established even up to about 99%. There were no false positive sonographic findings. Because of our good results we did not consider it necessary in recent time to perform an angiography before surgery in 25 patients. These patients had a high angiographic risk and there was a clear cut Doppler finding of an extreme stenosis in the internal carotid artery.

Carotid Artery Diseases↗
PubMed1979

Enzymes of agmatine degradation and the control of their synthesis in Klebsiella aerogenes.

The degradation of agmatine to succinate by Klebsiella aerogenes occurs in five steps. The enzyme catalyzing the first step, agmatinase, is induced by agmatine. The enzymes catalyzing the second and third steps, putrescine aminotransferase and 4-aminobutyraldehyde dehydrogenase, are induced by putrescine and also by their product, 4-aminobutyrate. The enzymes catalyzing the fourth and fifth steps, 4-aminobutyrate aminotransferase and succinate semialdehyde dehydrogenase, are induced by 4-aminobutyrate. This compound also serves as gratuitous inducer of the catabolic acetylornithine aminotransferase. The formation of the enzymes responsible for agmatine degradation is regulated not only by induction, but also by catabolite repression and activation by glutamine synthetase.

4-Aminobutyrate Transaminase↗
PubMed1978

Utilization of arginine by Klebsiella aerogenes.

Klebsiella aerogenes utilized arginine as the sole source of carbon or nitrogen for growth. Arginine was degraded to 2-ketoglutarate and not to succinate, since a citrate synthaseless mutant grows on arginine as the only nitrogen source. When glucose was the energy source, all four nitrogen atoms of arginine were utilized. Three of them apparently did not pass through ammonia but were transferred by transamination, since a mutant unable to produce glutamate by glutamate synthase or glutamate dehydrogenase utilized three of four nitrogen atoms of arginine. Urea was not involved as intermediate, since a unreaseless mutant did not accumulate urea and grew on arginine as efficiently as the wild-type strain. Ornithine appeared to be an intermediate, because cells grown either on glucose and arginine or arginine alone could convert arginine in the presence of hydroxylamine to ornithine. This indicates that an amidinotransferase is the initiating enzyme of arginine breakdown. In addition, the cells contained a transaminase specific for ornithine. In contrast to the hydroxylamine-dependent reaction, this activity could be demonstrated in extracts. The arginine-utilizing system (aut) is apparently controlled like the enzymes responsible for the degradation of histidine (hut) through induction, catabolite repression, and activation by glutamine synthetase.

Arginine↗
PubMed1978

Catabolic N2-acetylornithine 5-aminotransferase of Klebsiella aerogenes: control of synthesis by induction, catabolite repression, and activation by glutamine synthetase.

Klebsiella aerogenes formed two N2-acetylornithine 5-aminotransferases (ACOAT) which were separable by diethylaminoethyl-cellulose chromatography. One ACOAT was repressed when the cells grew on arginine-containing medium, indicating its function in arginine biosynthesis. The second ACOAT was induced when arginine or ornithine was present in the medium as the sole source of carbon or nitrogen, suggesting its function in the catabolism of these compounds. The induced enzyme was purified almost to homogeneity. Its molecular weight is 59,000; it is a pyridoxal 5-phosphate-dependent enzyme and exhibits activity with N2-acetylornithine (Km = 1.1 mM) as well as with ornithine (Km = 5.4 mM). ACOAT did not catalyze the transamination of putrescine or 4-aminobutyrate. The best amino acceptor was 2-ketoglutarate (Km = 0.7 mM). ACOAT formation was subject to catabolite repression exerted by glucose when ammonia was present in excess. When the cells were deprived of nitrogen, ACOAT escaped from catabolite repression. This activation was mediated by glutamine synthetase as shown by the fact that mutants affected in the regulation or synthesis of glutamine synthetase were also affected in the control of ACOAT formation.

Acetamides↗
PubMed1978

[Intraoperative bacterial contamination and posttraumatic wound infection (author's transl)].

In a consecutive series of 150 fractures treated surgically 16 wound infections were observed. Evaluating the intraoperative wound swabs, type and localisation of the fractures, duration of operation and tourniquet time it was tried retrospectively to find a relationship to these posttraumatic wound infections. The highest rate of infection was found in fractures of the tibia. Open fractures had a higher risk than closed ones. Furthermore, a prolonged duration of operation was related to a rising risk of infection. The intraoperative wound swabs themselves did not allow any conclusion concerning the risk of postoperative infection. Postoperative wound infections appeared nearly as frequent after negative as after positive intraoperative swab. Only the species of bacterias found intraoperatively allowed a conclusion concerning subsequent wound infection so far that after an intraoperative finding of gram-negative bacterias and - surprisingly - apathogenic sporogenic bacterias postoperative wound infections were observed more frequently than after finding other bacterias. In summary, however, the routine intraoperative wound swab does not seem to be suitable as a sreening-test for early recognation of impending postoperative wound infections.

Bacterial Infections↗
PubMed1977

Mechanical stability and post-traumatic osteitis: an experimental evaluation of the relation between infection of bone and internal fixation.

Stable and unstable internal fixation of fractures was performed in rabbits. After inoculation with Staphylococcus aureus, clinically manifest osteitis occurred only in the very unstable fractures. Abscesses, sinuses and sequestra developed in 45 per cent of the unstable fractures, whereas clinically manifest osteitis did not occur after rigid fixation. With rigid fixation there was no significant difference in the time to bony union between the infected and uninfected fractures. It seems that the development of osteitis and the healing of a fracture are both related to the degree of rigidity, but remain independent of each other. The significance of these findings in the management of posttraumatic osteitis is discussed.

Animals↗
PubMed1977

Urease of Klebsiella aerogenes: control of its synthesis by glutamine synthetase.

Urease was purified 24-fold from extracts of Klebsiella aerogenes. The enzyme has a molecular weight of 230,000 as determined by gel filtration, is highly substrate specific, and has a Km for urea of 0.7 mM. A mutant strain lacking urease was isolated; it failed to grow with urea as the sole source of nitrogen but did grow on media containing other nitrogen sources such as ammonia, histidine, or arginine. Urease was present at a high level when the cells were starved for nitrogen; its synthesis was repressed when the external ammonia concentration was high. Formation of urease did not require induction by urea and was not subject to catabolite repression. Its synthesis was controlled by glutamine synthetase. Mutants lacking glutamine synthetase failed to produce urease, and mutants forming glutamine synthetase at a high constitutive level also formed urease constitutively. Thus, the formation of urease is regulated like that of other enzymes of K. aerogenes capable of supplying the cell with ammonia or glutamate.

Enzyme Repression↗
PubMed1976

Aromatic amino acid biosynthesis in Alcaligenes eutrophus H 16 III. Properites and regulation of anthranilate synthase.

Properties and regulation of anthranilate synthase from Alcaligenes eutrophus H 16 were investigated. Anthranilate synthase was partially purified from crude extracts by affinity chromatography on tryptophan-substituted Sepharose, and was used for kinetic measurements. During the purification procedure the enzyme was stabilized by 50 mM L-glutamine or during chromatography on DEAE- cellulose and Sephadex G-200 with 30% glucerol, respectively.

Alcaligenes↗
PubMed1976

Purulent osteomyelitis of the cervical spine with epidural abscess. Operative treatment by means of dorsal and ventral approach.

The present case concerns an acute purulent osteomyelitis with an epidural abscess, located particularly in the intervertebral foramen between C5 and C6, which led to infection by staphylococci of the adjacent vertebral arches and vertebral bodies. An obstruction of the CSF passage was discovered by myelography at the level between C5 and C6. The bony tissue changed by inflammation was removed as far as possible by laminectomy. After irrigation of the epidural space with antibiotics and after control of the severe inflammation, the vertebral bodies C6 and C7 which were destroyed by the spreading inflammatory granulations, could be removed by a ventral approach 4 weeks later. The defect was filled with spongiosa chips. After immobilisation in a plaster shell and Crutchfield extension for 8 weeks the patient was slowly mobilized. A fusion of the vertebral bodies C5 and C6, C6/C7 and C7/C1 was achieved. A dislocation of the cervical spine did not occur and the patient recovered completely except for a paresis of the right hand. Treatment of this very rare and severe case was only possible by a combined dorsal and ventral procedure on the cervical spine.

Abscess↗
PubMed1976

Purification and properties of chorismate mutase-prephenate dehydratase and prephenate dehydrogenase from Alcaligenes eutrophus.

Chorismate mutase and prephenate dehydratase from Alcaligenes autophus H16 were purified 470-fold with a yield of 24%. During the course of purification, including chromatography on diethylaminoethyl (DEAE)-cellulose, phenylalanine-substituted Sepharose, Sephadex G-200 and hydrogyapatite, both enzymes appeared in association. The ratio of their specific activities remained almost constant. The molecular weight of chorismate mutase-prephenast dehydratase varied from 144,000 to 187,000 due to the three different determination methods used. Treatment of electrophoretically homogeneous mutase-dehydratase with sodium dodecyl sulfate dissociated the enzyme into a single component of molecular weight 47,000, indicating a tetramer of identical subunits. The isoelectric point of the bifunctional enzyme was 5.8. Prephenate dehydrogenase was not associated with other enzyme activities; it was separated from mutasedehydratase by DEAE-cellulose chromatgraphy. Chromatography on DEAE Sephadex, Sephadex G-200, and hydroxyapatite resulted in a 740-fold purification with a yield of 10%. The molecular weight of the enzyme was 55,000 as determined by sucrose gradient centrifugation and 65,000 as determined by gel filtration or electrophoresis. Its isoelectric point was pH 6.6. In the overall conversion of chorismate to phenylpyruvate, free prephenate was formed which accumulated in the reaction mixture. The dissociation of prephenate allowed prephenate dehydrogenase to compete with prephenate dehydratase for the substrate.

Alcaligenes↗