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Biomedical subjects

R Wagner

Publications and source records attributed to R Wagner.

At least 451 records · Page 25Linked to original sources
PubMed1984

[Positron emission tomography as a quantitative imaging method for demonstrating regional brain metabolism].

By means of positron emission tomography (PET) the distribution of certain isotopes in transverse sections through the body is visualized and the concentration of labelled tracers in the tissue quantified. Various biochemical and physiological processes in the brain can be followed by positron emitting radionuclides and compounds labelled thereby. Of these methods the measurement of glucose metabolism with 18fluorodeoxyglucose, of oxygen consumption with 15oxygen and of blood flow with 15O-carbon dioxide or 18fluoromethane are of greatest clinical relevance. These techniques demonstrated increases in metabolic rate after functional activation of respective brain regions and revealed local metabolic disturbances after different pathological changes of the central nervous system. With other labelled compounds protein synthesis, distribution of specific receptors, damage of the blood brain barrier, blood volume and regional uptake of drugs can be studied. PET thereby provides an insight in the biochemistry and the function of the brain which is at present not feasible with any other technology.

Adult↗
PubMed1983

[An automated procedure for the determination of the malignancy of tumorous tissue changes].

The accuracy of the "Histomat", an apparatus for automated histophotometric determination of malignant or benign tissues, was used on samples from 235 breast tumours (94 malignant and 141 benign tumours). Analysis of the measured data, using the schema developed by the manufacturer (Hytec), showed that in tumours of the breast this type of histophotometric analysis cannot distinguish between benign and malignant tissue changes. Its diagnostic use is therefore not justified.

Automation↗
PubMed1983

Morphology and chronology of ischemic mucosal changes in the small intestine. A light and electron microscopic investigation.

The morphology and chronology of an absolute ischemia was investigated on the small intestine of man and rat. It could be shown that the morphogenesis of ischemic damage to the intestinal mucosa in man does not differ from that in the rat. However, there are crucial and in therapeutic terms significant differences in the time course of the ischemic damage to the intestinal mucosa. Whereas in the small intestine of the rat, the first appreciable alterations - detachment and disruption of the lining epithelium at the villous tip - are already to be observed after absolute ischemia lasting 15 min, in the human small intestine the same lesions only occur after 4 h. A comparable complete necrosis of the small intestinal mucosa was detected in the rat after 7-h ischemia, and in man after 44-h ischemia.

Animals↗
PubMed1983

Comparison of Escherichia coli tRNAPhe in the free state, in the ternary complex and in the ribosomal A and P sites by chemical probing.

tRNAPheE.coli was modified at accessible guanosine, cytidine, and adenosine residues using the chemical modification method described by Peattie and Gilbert [Proc. Natl Acad. Sci. USA, 77, 4679-4689 (1980)]. Modification characteristics of the tRNA in the free state, in the ternary complex with elongation factor EF-Tu and GTP and in the ribosomal A and P sites were compared. A special procedure was devised to monitor, exclusively, tRNA molecules in the aminoacylated state. In the free tRNA, the most reactive bases are confined to the A73-C-C-A sequence of the aminoacyl stem, the anticodon loop, the D-loop and the extra loop and the results correlate well with the three-dimensional structure of tRNAPheyeast determined by X-ray studies. The pattern of reactivity was not affected either by charging the tRNA with phenylalanine or by labelling the 3' terminus with pCp. In the ternary complex, with elongation factor EF-Tu and GTP, changes in modification were observed at two sites, A73-C-C-A at the 3' terminus and C-13 and C-17 in the D-loop region, which are about 6 nm apart; no difference was observed in the anticodon loop. tRNAPhe bound at the ribosomal A or P sites exhibited similar, but not identical, modification patterns. Whereas nucleotides C-74 and C-75 were strongly protected at both sites, the adjacent A-73 showed an enhanced reactivity in the A site. The anticodon region G34-A-A-ms2.6(1)A was also strongly protected at both sites. In addition, nucleotide A-21 was protected during A-site, but not P-site, binding.

Binding Sites↗
PubMed1983

Composition of the Escherichia coli 70S ribosomal interface: a cross-linking study.

70S tight-couple ribosomes from Escherichia coli were cross-linked by using the bifunctional reagent phenyl-diglyoxal (PDG). The reaction was stopped after 4-h incubation while still in the linear range. In comparison with untreated ribosomes, 30% of those treated with PDG were shown, by sucrose gradient experiments, not to be separable into their subunits, but remained as 70S particles. There was no detectable change in the structure of the reacted particles when their sedimentation behavior was compared with that of native 70S controls. When the cross-linking reaction was performed in the presence of tRNAPhe and poly(U), the reacted ribosomes retained 40-50% of their tRNA binding activity. The reaction leads predominantly to the formation of RNA-protein cross-links but protein--protein as well as RNA-RNA cross-links could also be detected. Cross-linked material was extracted, and the individual RNAs were separated into 23S, 16S, and 5S RNAs. Proteins were identified electrophoretically after reversal of the RNA-protein cross-links. Proteins were found to be cross-linked to RNAs within and across the ribosomal subunits; the latter are considered to be close to or at the 70S subunit interface. The arrangement of RNA and protein at the subunit interface is discussed.

Aldehydes↗
PubMed1983

Structural investigation of Phe-tRNAPhe from E.coli bound to the ribosomal A-site.

Kethoxal modification of guanosines within Phe-tRNAPhe from E. coli was studied for tRNA in the free state and specifically bound to the ribosomal A-site. Complex formation with the ribosome results in a protection from chemical modification of two distant sites in the tRNA molecule. The guanosines affected are G-18 and G-19, located in the D-loop, and G-34 in the anticodon loop. Modification of Phe-tRNAPhe in the absence of ribosomes leads to a destabilisation of the tRNA structure. Our data are consistent with the conclusion that modification of G-34 at the anticodon loop triggers a conformational instability in distant parts of the tRNA molecule.

Aldehydes↗
PubMed1983

Application of conventional and FPG staining for the analysis of chromosome aberrations induced by low levels of dose in human lymphocytes.

Human peripheral lymphocytes were irradiated with 0.05-0.5 Gy of 220 keV X-rays. After application of either a conventional or the fluorescence plus Giemsa (FPG) staining technique, the dose response for dicentrics and acentrics was studied. The analysis of exclusively first-division cells (M1), carried out by the FPG method, revealed significantly higher aberration yields as compared with the results of the conventional method. The data from M1 cells support the assumption of a linear dose response for both dicentrics and acentrics. The results are discussed with regard to the application of chromosome analyses for a cytogenetic dosimetry after exposure to low levels of ionizing radiation.

Chromosome Aberrations↗
PubMed1983

[Manual labor and Dupuytren disease. The results of a computerized survey in the field of iron metallurgy].

A survey was made among ironworkers to determine if manual work had a special influence on the onset of Dupuytren's disease. In 5,206 workmen examined, 196 were affected, and a careful study of their working conditions showed a definite correlation between hard manual work over many years and the occurrence of Dupuytren's disease, especially in the younger age group. We observed that familial arterial hypertension is a contributory factor. Although Dupuytren's disease cannot be considered as an occupational disease, its development, is favored by hard manual work for at least 10 years. The initiating role of trauma, especially a fracture of the wrist, is confirmed.

Adult↗
PubMed1983

[Incomplete testicular feminisation].

We report a case of incomplete testicular feminisation in a 53 years old, third time married patient. Prominent symptoms were a slightly masculine structure of the body, masculine features and a hypertrophy of the clitoris. The reason for hospitalization was a lower abdominal tumour. Histologically it was a hydrocele with a testicle including a Leydig's cell-tumour without any signs of malignancy. On the opposite side was on atrophic testicle without spermiogenesis too. As usual the syndrome of incomplete testicular feminisation was discovered very late. Therefore, the necessary psychological guidance, especially from the beginning of puberty and the oncological control to exclude a tumour of the testicle had been left undone. It is the purpose of this report to draw attention to the aspect of this disease despite its rare occurrence in a ratio of 1:2,000 to 1:20,000.

Age Factors↗
PubMed1983

Hypometabolic cortical lesions in tuberous sclerosis with epilepsy: demonstration by positron emission tomography.

Four patients with a well-established diagnosis of tuberous sclerosis and grand mal type epileptic seizures as their principal clinical symptom were examined by conventional surface electroencephalography (EEG), X-ray computed tomography, and positron emission tomography (PET) using the [18F]-2-fluoro-2-deoxyglucose method. The interictal EEG showed various abnormalities of poor localizing value, but no focal epileptic discharges. X-ray computed tomography demonstrated subependymal calcifications in all cases, although cortical lesions were found only twice. However, in the PET images of each patient one or two localized cortical foci with a metabolic rate for glucose more than 40% lower than in the respective contralateral region were clearly delineated. It may be assumed that those hypometabolic areas represent the epileptogenic cortical tubers, which are characteristic of the disease but usually cannot be detected in vivo by other methods.

Adult↗
PubMed1983

Absence of the seventh component of complement in a patient with chronic meningococcemia presenting as vasculitis.

A previously healthy 40-year-old man presenting with fever, arthritis, and cutaneous vasculitis was found to have chronic meningococcemia. Evaluation of his complement system showed an absence of functional and antigenic C7, compatible with a complete deficiency of the seventh component of complement. Study of the patient's family spanning four generations showed heterozygous deficiency of C7 in five members. Chronic neisserial infection can be associated with C7 deficiency and must be distinguished from other causes of cutaneous vasculitis.

Adult↗
PubMed1983

["Left anterior hemiblock" or "extreme left axis deviation" in the ECG of children].

A comprehensive study involving the use of ECG's from children at the Giessen University Children's Hospital was conducted with the specific intent of identifying all children with an extreme left-axis deviation. This study showed that, in a time period of five years, 212 out of 3618 children examined electrocardiographically had an extreme left-axis deviation according to very strict criteria, their ECG-types could be divided into three groups: 1. without heart defects, 2. with congenital heart anomalies, 3. after surgery for congenital heart problems. Measurement of the QRS-complex in eighty children without heart defect showed that fifty-nine of the children (73.8%) had a vector -QRS between -30 degrees to -90 degrees. Ih the 88 children with congenital heart defects, and in 20 with an extreme left-axis deviation previous to surgery, an angle of -60 degrees to -90 degrees was found, most often in children with complete A-V canals of Down's Syndrome (as well as in children with transposition of the great arteries, univentricular heart or other complicated malformations of the heart). And finally, an extreme left axis deviation was very often found after surgery to correct Tetralogy of Fallot, ventricular defect, or endocardial cushion defect. Since an extreme left-axis deviation often occurs in children without heart defects, we would like to suggest that the term "Left anterior Hemiblock" be reserved for cases where there is certainty that damage to the conduction system has occurred. In all other cases, we prefer the term "left-axis deviation" as a more appropriate because an anomaly in the conduction system is more likely than a "block" i.e. an interruption of the conduction of electrical impulses through the heart muscle.

Adolescent↗
PubMed1983

Injuries of hepatic veins and retrohepatic vena cava.

Three cases of hepatic vein and retrohepatic inferior vena caval injuries are reported, and the literature is reviewed. Our experience, coupled with a critical review of the literature reveals that successful vascular isolation of the relatively inaccessible retrohepatic vena cava and/or hepatic veins is the key to optimal surgical management of major injuries to these structures. The various shunt techniques have been outlined with special emphasis made to the midline sternotomy incision as the incision of choice. This incision not only gives optimal exposure to the injured site, but also allows easy atrial-caval cannulation. If cross-clamping of the abdominal aorta is necessary, it can be easily done via a median sternotomy.

Accidents, Traffic↗
PubMed1982

A structural model of 5S RNA from E. coli based on intramolecular crosslinking evidence.

We describe new results obtained using the bifunctional chemical reagent phenyldiglyoxal (PDG) to study the intramolecular crosslinking of ribosomal 5S RNA from E. coli. In a previous publication (Wagner & Garrett [1]) we reported the identification of a crosslink in the stem region of 5S RNA (G2-G112) using the same reagent but were unable to obtain further information because of the presence of monofunctional adducts which confused the analyses. To overcome this problem, we have removed the monoaddition products by coupling them via their free reagent ends to a solid support bearing reactive groups. Using this system we have been able to identify a new crosslink G41-G72 in native 5S RNA which has considerable structural implications. We propose a structural model in which the proximity of both nucleotides is maintained by secondary interactions.

Base Sequence↗