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Biomedical subjects

R Hermann

Publications and source records attributed to R Hermann.

At least 19 recordsLinked to original sources
PubMed1992

Towards high resolution SEM of biological objects.

The major task of biological high resolution SEM and TEM is to provide structural information for correlating structure and function. It is the only methodology with the inherent power needed to observe structures down to molecular dimensions within the context of complex biological systems. Specimen preparation and imaging techniques should therefore be directed towards the preservation and imaging of the smallest significant details in order to fully exploit this unique, integrating feature of biological electron microscopy, complementing the progress of the techniques used in cell biology, biochemistry, and molecular biology.

Animals↗
PubMed1991

Interference with protein binding at AP2 sites by sequence-specific methylation in the late E2A promoter of adenovirus type 2 DNA.

The in vitro methylation of the +6, +24, and -215 located 5'-CCGG-3' sequences in the late E2A promoter of adenovirus type 2 (Ad2) DNA abrogates promoter function. 5-Methyldeoxycytidine (5-mC) at positions +6 and +24 in both or either of the two DNA complements in the late E2A promoter abolishes the formation of a high-molecular-mass DNA-protein complex that is essential for promoter function. The formation of this complex can be competed for by an oligodeoxyribonucleotide with a consensus AP2 sequence, but not by AP1, AP3, or CREB sequences. The AP2 sites comprise the +6 and +24 located 5'-CCGG-3' sequences in the late E2A promoter; the AP1, AP3 and CREB sequences are in their immediate vicinity. Methylation of either the +6 or the +24 5' -CCGG-3' sequence also compromises formation of the DNA-protein complex. A 40 nucleotide pair oligodeoxyribonucleotide encompassing the -215 5' -CCGG-3' site in the late E2A promoter can also form DNA-protein complexes which is not affected by the introduction of a 5-mC residue in the -215 position. The data suggest that the AP2 protein together with other proteins is involved in the generation of a transcription-activating complex with the late E2A promoter of Ad2 DNA, and the formation of this complex is completely abolished when both the +6 and +24 5'-CCGG-3' sequences are methylated.

Adenovirus Early Proteins↗
PubMed1991

High resolution biological scanning electron microscopy: a comparative study of low temperature metal coating techniques.

Structural information on the surface of biological specimens can be resolved within molecular dimensions by "in-lens" field emission scanning electron microscopes when cryo-methods are used to adequately preserve the native state of the specimen. The visual definition of molecular surface structures depends largely on the metal coating. The thickness of the coating, as well as the temperature at which it is deposited, are among the most important parameters affecting visual definition. These were evaluated on T4 polyheads and T4D phages using chromium double-axis rotary shadowing (DARS). Micrographs of optimally DARS coated T4 polyheads and T4D phages were compared with chromium planar-magnetron sputtering (PMS) and unidirectional shadowing with platinum/carbon. Metal deposition was carried out at low temperatures during all three procedures. Optimal visual definition of structural details on the surface of DARS coated T4 polyheads and T4D phages (capsomeres of T4 polyheads and their subunits with diameters of 8 and 3 nm; T4D phage tail fibres with a thickness of 3 nm) is achieved at a thickness of the chromium film greater than the minimum required for metal film coalescence. Chromium DARS coating at room temperature resulted in poor structural definition, whereas DARS at specimen temperatures of -85 degrees C and -150 degrees C, with the chromium thickness optimized for each temperature, yielded good visual detail of polyhead substructures. The visual definition was slightly reduced when DARS coating was carried out at a specimen temperature of -250 degrees C. Adequate structural visibility of T4D phage and T4 polyhead surface structures was achieved with the three coating techniques tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon↗
PubMed1991

High precision immunoscanning electron microscopy using Fab fragments coupled to ultra-small colloidal gold.

Ultra-small colloidal gold (less than 1 nm), bound to Fab fragments provides the shortest practical specific marker system to date and can be used in concert with field emission scanning electron microscopes to precisely locate antigenic sites. An "in-lens" FE-SEM equipped with a highly sensitive single crystal YAG-detector for backscattered electrons, as well as the use of advanced specimen preparation techniques based on cryofixation, are among the indispensible prerequisites. A T-even type Escherichia coli bacteriophage, Tu II*-46, was chosen to study properties of the immunogold labeling system. Distinct regions on the tail fibers of this phage were labeled with Fab fragments derived from antibodies against the related phage Tu II*-6. The tail fibers are composed of pairs of homologous proteins, thus offering two identical antigenic sites at the same locus on the tail fibers. Fab fragments can be visualized in the SEM at high accelerating voltage (30 kV) without any additional marker. This permits comparison of the labeling characteristics of unmarked and colloidal gold-marked Fab fragments. Unmarked Fab fragments often bind by pairs (two singlet Fab fragments bound opposed to each other along the axis of the tail fiber). The labeling efficiency of unmarked Fab fragments was greater than that of ultra-small gold-labeled Fab fragments. Binding by pairs was not seen after labeling with ultra-small gold-Fab fragments. The conjugates used in this study exhibited one colloidal gold per Fab fragment.

Animals↗
PubMed1991

[Characteristics of the QT interval in the ECG following reconstructive surgery of the common carotid artery].

In 40 patients undergoing thrombendarterectomy of the common carotid artery, the frequency-corrected QT interval in the ECG, as well as the serum sodium, potassium and total calcium were studied. Examination took place preoperatively 1.-3. hour postoperative and the 1. and 5. day postoperative. In 13 patients, pathological prolongation of QT interval (greater than 440 msec) was already found pre-operatively. Postoperative significant QT interval prolongations could not be found in any patient, independent of the site of operation or pre-operative findings. The total serum calcium concentration was postoperatively significantly reduced (P less than 0.01). There was no correlation between the reduced total serum calcium and the QT interval in the ECG. The findings contradict the assumption that clinically relevant reduction of the autonomous cardial innervation is frequent in patients undergoing thromboendarterectomy of the common carotid artery.

Aged↗
PubMed1991

Effects of long-term inhalation of N-nitrosodimethylamine in rats.

The toxicological evaluation and histopathological findings of a long-term inhalation study in progress with N-nitrosodimethylamine (NDMA) are presented. Exposure was to three concentrations of NDMA: 0.04, 0.2 and 1.0 ppm (corresponding to 120, 600 and 3000 micrograms/m3). A significant reduction in median survival time (nine months) was seen in animals treated with the highest concentration of NDMA. Tumours occurred mainly in the nasal cavity, with the highest incidences in the groups receiving 1.0 and 0.2 ppm NDMA (19/36 and 31/36 tumour-bearing animals); in the lowest exposure group, 13/36 nasal tumours have been observed. The survival time of this treatment group, however, was about two months longer than that of the controls.

Administration, Inhalation↗
PubMed1990

The effect of the radioprotector WR-2721 and WR-1065 on mitochondrial lipid peroxidation.

The radioprotective agent WR-2721 is dephosphorylated to the free thiol form WR-1065 in vivo. The effects of WR-2721, WR-1065 and reduced glutathione on a mitochondrial lipid peroxidation system were compared. WR-2721 had no effect on mitochondrial lipid peroxidation in vitro, and could not prevent the inactivation of mitochondrial enzymes. Both WR-1065 and glutathione were effective inhibitors of mitochondrial lipid peroxidation induced by ADP/Fe/NADPH or by ADP/Fe/ascorbate. Both thiols correspondingly delayed the free radical-mediated inactivation of succinate dehydrogenase and isocitrate dehydrogenase. WR-1065 was able to reduce cumene hydroperoxide non-enzymatically, and proved to be weak substrate for glutathione peroxidase. The disulfide formed from WR-1065 could be reduced by glutathione without the participation of glutathione reductase. A redox cycle is proposed between WR-1065, glutathione and glutathione reductase to explain the inhibitory effect of WR-1065 on lipid peroxidation.

Amifostine↗
PubMed1989

Sequence-specific methylation in a downstream region of the late E2A promoter of adenovirus type 2 DNA prevents protein binding.

In studies on the promoter-inhibitory effect of sequence-specific DNA methylations, the late E2A promoter of human adenovirus type 2 (Ad2) has been used as an experimental tool. Upon the in vitro methylation of 5'-CCGG-3' (HpaII) sequences at nucleotides +24, +6 and -215 relative to nucleotide + 1, the site of transcriptional initiation, promoter inhibition or inactivation has been demonstrated in transient expression tests in Xenopus laevis oocytes (Langner et al., 1984), in mammalian cells (Langner et al., 1986), after the genomic fixation of the promoter in conjunction with a reporter gene in mammalian cells (Müller & Doerfler, 1987), and in a cell-free transcription system employing nuclear extracts of human HeLa cells (Dobrzanski et al., 1988). Possible explanations for the inhibitory effect of three 5-methyldeoxycytidine (5-mC) residues in a promoter sequence are structural alterations in DNA or the positive or negative modulation of the sequence-specific binding of proteins. This modulation could be indirect at the level of protein-protein interactions. A synthetic oligodeoxyribonucleotide of 50 base-pairs (bp) or a restriction endonuclease fragment of 73 bp in length, which comprised the +24 and +6 5'-CCGG-3' sequences of the late E2A promoter, were methylated or hemimethylated at these two sites, or were left unmethylated and were subsequently incubated with a partly purified (heparin-Sepharose) nuclear extract of human HeLa cells. Protein binding was monitored by electrophoretic migration delay of the 32P-labeled 50 bp oligodeoxyribonucleotide or the 73 bp fragment on polyacrylamide gels. The formation of one of the DNA-protein complexes in this analysis was compromised when 5'-CCGG-3' methylated oligodeoxyribonucleotides were used in the binding assays. Similar results were obtained when the 50 bp oligodeoxyribonucleotide was hemimethylated in either complement.The formation of the same complex could also be obliterated by adding the same non-methylated oligodeoxyribonucleotide as competitor to the reaction mixture. The methylated oligodeoxyribonucleotide did not act as a competitor, nor did a randomly composed oligodeoxyribonucleotide of identical length. The results show that protein binding is abolished by methylation of those sequences in the late E2A promoter whose methylation inhibits promoter function. The abrogation of protein binding has been observed with a 50 bp or 73 bp fragment. With a 99 bp or a 377 bp fragment, binding differences between the unmethylated and the 5'-CCGG-3' methylated late E2A promoter are not apparent.

Adenovirus Early Proteins↗
PubMed1989

Effect of long-term inhalation of N-nitroso-dimethylamine (NDMA) and SO2/NOx in rats.

This report focusses on preliminary results of a long-term inhalation assay with N-nitroso-dimethylamine (NDMA) at low concentrations. Chronic inhalation of 1 ppm of NDMA (4 h/day, 5 days/week) was found to be toxic in rats and diminished life expectancy by about 8 months compared to the control group. Mostly tumors of the nasal region (25/36) were observed. Inhalation of 0.2 ppm of NDMA lead to a high tumor yield in rats (20/36). At a concentration of 0.04 ppm (= 0.12 mg/m3 in air) 3 tumors of the nasal region have been found until now. In addition, a combined inhalation study of other air pollutants SO2 or NOx together with NDMA at the 0.2 ppm level is being performed. Tumors of the nasal region have been observed in the groups with SO2 + NDMA and NOx + NDMA as well as with NDMA alone. Differences in tumor response of the groups treated with NDMA alone or in combination with SO2/NOx cannot be assessed yet. The additional treatment with the air pollutants SO2 or NOx has not affected the body weight gain or any other observable parameters of the life quality of the rats.

Administration, Inhalation↗
PubMed1989

[Prolongation of the QT interval in the ECG following surgery of the neck (neck dissection)].

The QT interval on the ECG was determined in 40 patients undergoing major resection plus neck dissection. The readings were taken before operation, between 1 and 3 h after operation, and the 1st and the 7th day after the operation. The QT interval was prolonged significantly more often and more intensively in patients undergoing surgery on the right side (from 411 +/- 17 to 459 +/- 50 ms) than in those operated on the left side (409 +/- 14 to 431 +/- 32 ms; all values mean +/- SD). The cause of the prolongation of QT interval is thought to be either direct surgical damage to the sympathetic cardiac nerves during the operation, or a temporary disturbance of nerve function due to pressure, tension or oedema in the wound. An explanation for the observed side difference might be differing functional effects of right- and left-sided sympathetic innervation of the heart. Attention is drawn to the meaning of these findings as a predisposing factor for ventricular tachyarrhythmias.

Adult↗
PubMed1988

Rat hepatic sinusoidal endothelial cells in monolayer culture. Biochemical and ultrastructural characteristics.

Sinusoidal endothelial cells were isolated by collagenase-pronase digestion of rat livers followed by centrifugal elutriation. The main endothelial cell fraction consisted of more than 85% endothelial cells as shown by electron microscopy and enzyme histochemistry. Contamination by Kupffer cells was less than 5%. The endothelial cells formed a coherent stable monolayer on dishes coated with collagen type IV in the presence of an RPMI 1640 medium supplemented with 4% Ultroser. Fc receptors were undetectable immediately after elutriation but reappeared after 12 h in culture. Von Willebrand factor (formerly factor VIII-related antigen) could not be detected unequivocally by immunofluorescence. Unchallenged endothelial cells did not produce eicosanoids. In the presence of free arachidonate, however, prostaglandins D2 and E2 as well as thromboxane B2 and 6-keto-prostaglandin F1 alpha were detected by radioimmunoassay and by high-performance liquid chromatography analysis of [3H]arachidonate-exposed cells. Cells treated with the Ca2+ ionophore A23187 produced the same spectrum of immunologically measured prostanoids. In contrast to Kupffer cells in primary culture, eicosanoid formation by endothelial cells was neither triggered by phagocytotic stimuli nor suppressed by pretreatment with dexamethasone.

Animals↗
PubMed1987

Enhancement of neutrophil adherence to isolated rat liver sinusoidal endothelial cells by supernatants of lipopolysaccharide-activated monocytes. Role of tumor necrosis factor.

Supernatants of endotoxin-activated monocytes have been shown to stimulate human neutrophil adherence to rat liver sinusoidal endothelial cells 3-4-fold. Evidence will be presented that tumor necrosis factor (TNF) is responsible for this phenomenon: (a) in high-performance gel filtration of supernatants of lipopolysaccharide-activated monocytes, neutrophil adhesion-inducing activity coeluted with TNF activity measured in the L929 cell-lysing assay at 25-45 kDa; (b) anti-TNF antibody treatment of supernatants of activated macrophages abolished their adhesion-inducing activity; (c) human recombinant TNF alpha stimulated neutrophil adhesion to sinusoidal endothelial cells in a dose-dependent manner. In addition, polymyxine B sulfate, which was capable of neutralizing direct effects of lipopolysaccharide on neutrophil adhesion, could abolish neither the neutrophil-adhesion-inducing activity of the supernatants of endotoxin-activated monocytes nor the effect of human recombinant TNF itself. The neutrophil-adhesion-inducing activity was due both to a direct activation of neutrophils and to an influence of the sinusoidal endothelium itself by TNF: pretreatment of sinusoidal endothelial cells with TNF followed by thorough washing resulted in an increased neutrophil attachment. Protein synthesis by endothelial cells was not required. However, incubation of sinusoidal endothelium with TNF followed by anti-TNF antibody treatment abrogated the increased neutrophil adhesion. This suggests that TNF bound to sinusoidal endothelial cell surfaces was responsible for neutrophil adhesion. It is concluded that TNF by increasing granulocyte sticking to the endothelial lining of the liver sinusoids may play a significant role in endotoxin-induced inflammation of the liver as it is found in the septic state.

Animals↗
PubMed1986

Simultaneous panic and depressive disorders: clinical and sleep EEG correlates.

Panic and depressive symptoms occur simultaneously in many depressed patients. To study the frequency of this association and to determine whether patients with simultaneous panic and major depression differed from those with only major depressive disorder (MDD) in clinical features and in sleep electroencephalographic (EEG) variables, we evaluated a total sample of 336 patients with MDD. Fifty-eight (17%) had both panic and MDD; 50 had complete data and were matched for age and severity of illness with other patients having only MDD. Patients with simultaneous panic and depression had significantly higher ratings for psychic and somatic anxiety, and rapid eye movement (REM) latencies approximating normal values. Patients with only MDD (without panic disorder) rated significantly higher in guilt feelings and had shorter REM latencies. Our results suggest that the simultaneous occurrence of panic and depression is relatively frequent, is accompanied by differences in sleep EEG variables, and may have implications for treatment.

Adult↗
PubMed1986

Effect of recombinant human interferon gamma and interleukin 2 on CFU-GM.

Human bone marrow CFU-GM were cultured with rHu-GM-CSF and varying concentrations of rHu-gamma-IFN. Concentration-dependent suppression of CFU-GM precursors by gamma-IFN was demonstrated. This suppression was, in part, reversible by addition of rHu-IL-2. Reversal was also concentration-dependent. Both immune-regulatory T-cell mediators seem to act on a more primitive stage of committed progenitor cell development.

Bone Marrow Cells↗