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Biomedical subjects

B Freitag

Publications and source records attributed to B Freitag.

At least 19 recordsLinked to original sources
PubMed2005

Breaking the spherical and chromatic aberration barrier in transmission electron microscopy.

Since the invention of transmission electron microscopy (TEM) in 1932 (Z. Physik 78 (1932) 318) engineering improvements have advanced system resolutions to levels that are now limited only by the two fundamental aberrations of electron lenses; spherical and chromatic aberration (Z. Phys. 101 (1936) 593). Since both aberrations scale with the dimensions of the lens, research resolution requirements are pushing the designs to lenses with only a few mm space in the pole-piece gap for the specimen. This is in conflict with the demand for more and more space at the specimen, necessary in order to enable novel techniques in TEM, such as He-cooled cryo electron microscopy, 3D-reconstruction through tomography (Science 302 (2003) 1396) TEM in gaseous environments, or in situ experiments (Nature 427 (2004) 426). All these techniques will only be able to achieve Angstrom resolution when the aberration barriers have been overcome. The spherical aberration barrier has recently been broken by introducing spherical aberration correctors (Nature 392 (1998) 392, 418 (2002) 617), but the correction of the remaining chromatic aberrations have proved to be too difficult for the present state of technology (Optik 57 (1980) 73). Here we present an alternative and successful method to eliminate the chromatic blur, which consists of monochromating the TEM beam (Inst. Phys. Conf. Ser. 161 (1999) 191). We show directly interpretable resolutions well below 1A for the first time, which is significantly better than any TEM operating at 200 KV has reached before.

Lenses↗
PubMed2004

[Implantable drug pumps for spinal opioid analgesia: technical solutions and problems].

Among the many technical appliances for pain therapy which are currently available, the use of implantable drug pumps for prolonged pain treatment is of increasing importance. Since this kind of pain therapy can be used without any problems outside the hospital, it improves the quality of life of the patient. Furthermore, it is combined with a reduction of side-effects which frequently occur when analgesics are given orally or parenterally in big single doses. High initial costs are compensated by a good cost-benefit ratio of this kind of pain treatment, which enables the use of analgesics in low doses in out-patients. Based on the use of gas mixtures which can be compressed repeatedly, implantable mechanically-driven pumps are a nearly inexhaustible propulsion unit for drug infusions. The development of new gas mixtures and of innovative control mechanisms allows greater independence from surrounding influences and higher precision regarding infusion rates. Mechanically-driven pumps are characterized by prolonged functioning and low cost of purchase. Therefore, they will continue to be available on the medical market in future. Special progress in cardiac pacemaker therapy as well as further miniaturization of portable infusion pumps with peristaltic propulsion have led to the development of programmed implantable pumps with lithium batteries as energy sources. The advantages of these pumps, particularly those with "externally" programmable infusion rates (continuous, bolus, periodical bolus, etc.) point to the future. With these devices, evacuation and refilling of the pumps due to necessary changes of drug concentrations, as has to be done with mechanically working pumps with fixed infusion rates, are no longer necessary. Therefore, these programmable pumps can also be used for infusion of drug concentrates. At present, however, high costs and the battery-dependent limited duration of functioning of these devices are disadvantageous. As with cardiac pacemakers, battery exchange is necessary. Using implantable drug pumps, relevant changes of body temperature and atmospheric pressure lead to more or less considerable deviations of the infusion rates. These deviations differ from product to product and can be studied in the informative material published by the manufacturer.

Analgesics, Opioid↗
PubMed2003

Electron energy-loss near-edge structures of 3d transition metal oxides recorded at high-energy resolution.

Near-edge fine structures of the metal L(2,3) and O K-edges in transition metal-oxides have been studied with a transmission electron microscope equipped with a monochromator and a high-resolution imaging filter. This system enables the recording of EELS spectra with an energy resolution of 0.1eV thus providing new near-edge fine structure details which could not be observed previously by EELS in conventional TEM instruments. EELS-spectra from well-defined oxides like titanium oxide (TiO(2)), vanadium oxide (V(2)O(5)), chromium oxide (Cr(2)O(3)), iron oxide (Fe(2)O(3)), cobalt oxide (CoO) and nickel oxide (NiO) have been measured with the new system. These spectra are compared with EELS data obtained from a conventional microscope and the main spectral features are interpreted. Additionally, the use of monochromised TEMs is discussed in view of the natural line widths of K and L(2,3) edges.

Journal Article↗
PubMed2003

Optimization of EDX performance in Tecnai TEMs.

The quality of X-ray spectra from FEGTEMs has been improved by three different means: the use of beryllium shields, improved collimation and improved specimen holder geometry. The improvements lead to a significant increase in peak-to-background ratios and a reduction in spurious peaks in the EDX spectra. A double-tilt, low-background specimen holder was designed to allow EDX analysis at 0 degrees of tilt without shadowing.

Journal Article↗
PubMed2001

[Postoperative nausea and vomiting--still a problem?].

Based on a questionnaire of the General Hospital of Hamburg-Altona, we asked 738 patients about postoperative complaints such as nausea, vomiting, pain in the operating field and feeling of coldness in order to record the quality of the results of operation and anaesthesia in 1997 and 1998. The incidence of nausea and vomiting amounted to only 29% on average. One of our earlier studies of postoperative vomiting from 1995-1997 and the results gained from a control group of non-treated patients in our ondansetron study from 1995, which was conducted using information drawn from the routinely-used anaesthesia protocol and was therefore limited to data from the immediate pre- and postoperative period up to discharge of the patients from the recovery ward, showed much higher frequencies of nausea and vomiting (44 and even 66% on average, respectively). We cannot definitely evaluate whether the reduction in the average rates of nausea and vomiting in our present study is due to the additional preoperative application of 150 mg vomex supp. and 1.0-2.5 mg dehydrobenzperidol and/or 20-30 mg metoclopramid given i.v. shortly before the end of anaesthesia or to more intensive observation of non-medicinal prophylactic possibilities. But when we look at the frequency of nausea and vomiting in special groups of our present study, we can still find unacceptably high rates of nausea and vomiting, for instance 40% after cholecystectomies and abruptios and even 50% after struma operations. This shows that a satisfactory solution to this problem has not yet been found--partly due, unfortunately, to financial restrictions. Nevertheless, for 15% of the patients postoperative nausea and vomiting were of only minor importance for general satisfaction with the treatment given them. This was probably due to good premedication of amnestic after-effects of narcosis.

Adolescent↗
PubMed2001

[C1-esterase inhibitor in ACE inhibitor-induced severe angioedema of the tongue].

Angio-oedema are often massive but temporary swellings of the soft tissue of the face or the throat, which can also affect other regions of the human body (e.g. the skin or internal organs). An oedema of the face and throat represents a life-threatening situation. Apart from the clinical condition of the patient and detailed knowledge of the medical history (incl. medical applications), the treatment should depend on the different pathogenesis. In this reported case, we describe the severe clinical development of an angio-oedema under a long-term treatment with an ACE-inhibitor, which in the end was only successfully treated with the application of a C1 inhibitor concentrate.

Airway Obstruction↗
PubMed2000

Inelastic electron holography

Coherence of inelastically scattered electrons was investigated by means of biprism interference experiments performed in a transmission electron microscope equipped with a highly coherent field emission gun and an imaging filter. The experimental results show that within the wave inelastically scattered at aluminium plasmons there is in fact an area of about 10 nm diameter with coherence sufficient to take electron holograms.

Journal Article↗
PubMed2000

A myxozoan-like parasite causing xenomas in the brain of the mole, Talpa europaea L., 1758 (Vertebrata, Mammalia).

Light and transmission electron microscopy revealed pericytes of brain capillaries of moles (Talpa europaea L., 1758) as parasitized intracellularly. These host cells were enlarged and of globular or ellipsoid shape, and incorporated a cell-within-cell sequence of primary, secondary and, rarely found, tertiary developmental stages of an eukaryotic organism. Other stages like spores were not discovered either in brain or in other organs. Due to the vertebrate host, and the parasitic cells showing the enveloped state this parasite can be classified as belonging to the Myxozoa rather than Paramyxea. Since spores, which would allow an exact identification of the parasite, could not be detected and mammals are very unusual hosts for Myxozoa, the parasite was designated a myxozoan-like organism.

Animals↗
PubMed1999

Element specific imaging with high lateral resolution: an experimental study on layer structures.

Planar defects and individual layers in ceramic material are chemically imaged by high resolution energy-filtering TEM using a post-column imaging electron energy filter. Objects are barium layers in the cuprate superconductor NdBa2Cu3O7-delta (isostructual to YBa2Cu3O7-delta) as well as planar defects and precipitates of beta-WB in tungsten- and chromium-doped TiB2. The barium layers with a spacing of 0.42 nm in the cuprate are resolved in jump-ratio images using the Ba_N edge. In the boride system the beta-WB precipitates with thickness of 0.8 nm can be chemically imaged in elemental maps of B_K, Ti_L,Cr_L and W_M. The B as well as the Ti map show a decrease in intensity at the precipitates, whereas in the W map an increase in intensity is observed. The boron-deficient layers with a spacing of 0.38 nm in the beta-WB precipitate can be resolved in boron jump-ratio images. Additionally, defects containing single boron-deficient layers are chemically imaged. Hence structures in the dimension of interatomic distances can be imaged with respect to their elemental constituents. Although high resolution electron spectroscopic images contain strong interference contrast from elastic scattering, after normalization or background subtraction the element specific images are dominated by chemical contrast.

Journal Article↗
PubMed1995

Stem cell factor binding to retrovirus primer binding site silencers.

Using modified nuclear lysis and binding conditions, we have examined the binding of an embryonal carcinoma (EC) cell factor, binding factor A, to a stem cell-specific silencer which acts at the DNA level and overlaps the Moloney murine leukemia virus (M-MuLV) proline primer binding site (PBS). Following our protocol, we found that in vitro binding of factor A correlated with the in vivo activity of the M-MuLV silencer. Factor A bound specifically to the wild-type silencer element at room temperature and 30 degrees C, but not at 4 degrees C, and bound 10-fold better to the full-length silencer than to a minimal silencer core element. The factor was enriched in nuclear compared with cytosolic extracts and in undifferentiated EC cells compared with differentiated cells in which the silencer is nonfunctional. Salt and ion requirements for factor A binding were investigated, and partial purification steps indicated the factor to be a heparin-Sepharose-binding moiety of greater than 100 kDa. To examine possible relationships between silencer and PBS activities, sequences representing phenylalanine, isoleucine, lysine-1,2, lysine-3, methionine, and tryptophan PBS DNA fragments were tested in vivo for stem cell-specific repression of M-MuLV expression and in vitro in DNA binding assays. Of these PBS elements, only the lysine-1,2 PBS DNA fragment showed consistently high levels of repression. Interestingly, the lysine-1,2 PBS DNA fragment also formed a complex with an EC cell factor with characteristics similar to those of factor A. However, the two factors did not cross-compete in binding studies, suggesting that they may be different but related factors. Our results suggest that expression of Mason-Pfizer monkey virus, visna virus, and spumavirus, which use the lysine-1,2 PBS, may be inhibited in undifferentiated stem cells.

Base Sequence↗
PubMed1994

Laparoscopic cholecystectomy in a young girl.

Laparoscopic cholecystectomy is now a widely used procedure in adults. However, reports on this procedure in infants and young children are rare. This paper reports a successful laparoscopic cholecystectomy in a young girl.

Child, Preschool↗
PubMed1994

[Acute abdomen--anesthesiologic and intensive care management].

The expression "acute abdomen" is a provisional destination of a complex of various abdominal diseases which require quick diagnostic as well as urgent surgical therapy. A close interdisciplinary cooperation during the whole perioperative period is of high importance for the prognosis of this potentially life-threatening syndrome. The anesthetist must have profound knowledge on causes and clinical signs of this disease, on diagnostic measures and on therapeutic principles. Anaesthesiological problems arise from the discrepancy between an urgent operation on one hand and the necessity of an improvement of the preoperative status of the patient on the other. Furthermore, these patients have high risks of aspiration due to disturbed motility of the gastrointestinal tract. Intensive therapy of these patients is characterized by the peculiarity that a primarily local abdominal disease is frequently followed by severe extraperitoneal general reactions and multiple organ failure, respectively.

Abdomen, Acute↗
PubMed1993

Characterization of the Moloney murine leukemia virus stem cell-specific repressor binding site.

The Moloney murine leukemia virus (M-MuLV) repressor binding site (RBS) mediates cell-type-specific repression in embryonal carcinoma (EC) cells of expression from several different promoters, including the M-MuLV long terminal repeat promoter. Silencing has been shown to depend on an element normally located in the proviral 5' noncoding region and occurs at the DNA level in the absence of retroviral proteins. Using fragments of the RBS region, we now show that the minimal size of the silencer corresponds to M-MuLV nt 147-163 and overlaps with the retroviral primer binding site region by 17 of its 18 bp. A panel of point mutations within the RBS has been examined to yield a consensus RBS sequence which is consistent with the notion that a previously identified nuclear factor (binding factor A) mediates RBS repression. Viral vectors using neomycin, beta-galactosidase, and luciferase reporters have been employed to show that RBS-mediated repression occurs in EC and embryonal stem, but not in other tested cell types. Repression was observed to occur within 48 hr of infection, prior to when global methylation of proviruses has been reported to occur. Repression also occurred after azacytidine treatment of EC cells, supporting the notion that the RBS functions independently of provirus methylation. However, levels of provirus methylation in selected cells were increased in the presence of a wild-type RBS, and methylation correlated with a secondary stage of virus repression. Thus, the M-MuLV RBS acts directly to control expression in EC cells and also appears to trigger a secondary level of repression which is coincident with provirus methylation.

3T3 Cells↗
PubMed1991

The effect of cisapride on gastro-oesophageal dysfunction in systemic sclerosis: a controlled manometric study.

1. Cisapride is a novel prokinetic drug which facilitates or restores motility throughout the gastrointestinal tract. Its mechanism of action is thought to involve enhancement of acetylcholine release in the myenteric plexus of the gut. 2. The effect of intravenous cisapride 10 mg on gastro-oesophageal dysfunction was investigated in 20 patients with systemic sclerosis, using a double-blind, randomised, cross-over, placebo-controlled manometric study design. 3. The increase in lower oesophageal sphincter pressure was significantly higher after cisapride (mean +/- s.e. mean, 8.3 +/- 2.1 cm H2O) than after placebo (mean +/- s.e. mean. 0.1 +/- 0.3 cm H2O) (P less than 0.001). The increase in the number of fundic gastric contractions during the 30 min study period was significantly higher after cisapride (mean +/- s.e. mean, 7.7 +/- 2.3) than after placebo (mean +/- s.e. mean, 0.9 +/- 0.6) (P less than 0.01). 4. No serious clinical adverse effects were observed. 5. The study demonstrates that intravenous cisapride induces a significant increase in lower oesophageal sphincter pressure and in the number of fundic gastric contractions, which may be beneficial in the treatment of scleroderma gastro-oesophageal dysfunction. Further long-term studies of the effect of oral cisapride in patients with systemic sclerosis are warranted.

Cisapride↗
PubMed1985

Effects of ketanserin on platelet function and red cell filterability in hypertension and peripheral vascular disease.

Serotonin is a vasoactive substance that acts on blood vessels and platelets but whose primary action lies in its role as an amplifier for other agents. The aim of this work was to study the effects on blood platelets and erythrocytes of the S2-serotonergic receptor antagonist ketanserin. Twenty-seven patients with untreated hypertension and/or intermittent claudication received a bolus intravenous (i.v.) injection of 10 mg ketanserin followed by 2 mg/h during 3 h i.v. infusion. Platelet function and erythrocyte filterability were studied before and 30 min, 3 h, and 24 h after the bolus injection. The results showed decreases of plasma beta-thromboglobulin and platelet factor 4 levels (p less than 0.001) and platelet aggregation induced by epinephrine plus serotonin (p less than 0.001), whereas ADP-induced aggregation remained unchanged 30 min and 3 h after ketanserin administration. Red cell filterability was decreased (p less than 0.01). There was a tendency toward lower mean arterial blood pressure but heart rate remained unchanged. The dual effect of ketanserin on platelet function and erythrocyte filterability might be of great clinical value in hypertension and peripheral vascular disease in which microcirculatory flow is altered.

Adult↗