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Biomedical subjects

S Reichelt

Publications and source records attributed to S Reichelt.

At least 19 recordsLinked to original sources
PubMed2005

Recovery of nanoparticles produced in phosphatidylcholine-based template phases.

This paper focuses on the characterization and use of polymer-modified phosphatidylcholine (PC)/sodium dodecyl sulfate (SDS)-based inverse microemulsions as a template phase for BaSO4 nanoparticle formation. The area of the optically clear inverse microemulsion phase in the isooctane/hexanol/water/PC/SDS system is not significantly changed by adding polyelectrolytes, i.e., poly(diallyldimethylammonium chloride) (PDADMAC), or amphoteric copolymers of diallyldimethylammonium chloride and maleamid acid to the SDS-modified inverse microemulsion. Shear experiments show non-Newtonian flow behavior and oscillation experiments show a frequency-dependent viscosity increase (dilatant behavior) of the microemulsions. Small amounts of bulk water were identified by means of differential scanning calorimetry. One can conclude that the macromolecules are incorporated into the individual droplets, and polymer-filled microemulsions are formed. The polymer-filled microemulsions were used as a template phase for the synthesis of BaSO4 nanoparticles. After solvent evaporation the nanoparticles were redispersed in water and isooctane, respectively. The polymers incorporated into the microemulsion are involved in the redispersion process and influence the size and shape of the redispersed BaSO4 particles in a specific way. The crystallization process mainly depends on the type of solvent and the polymer component added. In the presence of the cationic polyelectrolyte PDADMAC the crystallization to larger cubic crystals is inhibited, and layers consisting of polymer-stabilized spherical nanoparticles of BaSO4 (6 nm in size) will be observed.

Journal Article↗
PubMed2003

Re-evaluation of differential phase contrast (DPC) in a scanning laser microscope using a split detector as an alternative to differential interference contrast (DIC) optics.

In this paper, differential phase imaging (DPC) with transmitted light is implemented by adding a suitable detection system to a standard commercially available scanning confocal microscope. DPC, a long-established method in scanning optical microscopy, depends on detecting the intensity difference between opposite halves or quadrants of a split photodiode detector placed in an aperture plane. Here, DPC is compared with scanned differential interference contrast (DIC) using a variety of biological specimens and objective lenses of high numerical aperture. While DPC and DIC images are generally similar, DPC seems to have a greater depth of field. DPC has several advantages over DIC. These include low cost (no polarizing or strain-free optics are required), absence of a double scanning spot, electronically variable direction of shading and the ability to image specimens in plastic dishes where birefringence prevents the use of DIC. DPC is also here found to need 20 times less laser power at the specimen than DIC.

Animals↗
PubMed2001

Engaging refugee families in therapy: exploring the benefits of including referring professionals in first family interviews.

The possible benefits of including referring professionals in the first family interviews are being explored as a way to engage refugee families in therapy. Families in exile confront a number of problems related both to premigration traumatic exposures and to present adaptation processes. Refugee clients and the referring professionals in the larger system frequently see the problems and their solutions quite differently. This situation may often result in unclear working alliances in a context of therapy. We will describe first family interviews in which referring professionals are interviewed about their reasons for referrals, and where the families are invited to discuss these considerations. The conversations permit families, referrers, and therapists to reflect upon differences in positions and perspectives. Their experiences suggest that agreements or contracts based on these joint interviews are less ambiguous and more clearly formulated than contracts based on interviews with families alone. Finally, these experiences are discussed as a potentially valuable approach in a cross-cultural context.

Adult↗
PubMed1999

Dinitroaniline herbicide-resistant transgenic tobacco plants generated by co-overexpression of a mutant alpha-tubulin and a beta-tubulin.

Dinitroaniline herbicides are used for the selective control of weeds in arable crops. Dinitroaniline herbicide resistance in the invasive weed goosegrass was previously shown to stem from a spontaneous mutation in an alpha-tubulin gene. We transformed and regenerated tobacco plants with an alpha/beta-tubulin double gene construct containing the mutant alpha-tubulin gene and showed that expression of this construct confers a stably inherited dinitroaniline-resistant phenotype in tobacco. In all transformed lines, the transgene alpha- and beta-tubulins increased the cytoplasmic pool of tubulin approximately 1.5-fold while repressing endogenous alpha- and beta-tubulin synthesis by up to 45% in some tissues. Transgene alpha- and beta-tubulin were overexpressed in every plant tissue analyzed and comprised approximately 66% of the total tubulin in these tissues. Immunolocalization studies revealed that transgene alpha- and beta-tubulins were incorporated into all four microtubule arrays, indicating that they are functional. The majority of the alpha/beta-tubulin pools are encoded by the transgenes, which implies that the mutant alpha-tubulin and the beta-tubulin can perform the majority, if not all, of the roles of microtubules in both juvenile and adult tobacco plants.

Aniline Compounds↗
PubMed1999

Characterization of the unconventional myosin VIII in plant cells and its localization at the post-cytokinetic cell wall.

Myosins are a large superfamily of motor proteins which, in association with actin, are involved in intra- cellular motile processes. In addition to the conventional myosins involved in muscle contractility, there is, in animal cells, a wide range of unconventional myosins implicated in membrane-associated processes, such as vesicle transport and membrane dynamics. In plant cells, however, very little is known about myosins. We have raised an antibody to the recombinant tail region of Arabidopsis thaliana myosin 1 (a class VIII myosin) and used it in immunofluorescence and EM studies on root cells from cress and maize. The plant myosin VIII is found to be concentrated at newly formed cross walls at the stage in which the phragmoplast cytoskeleton has depolymerized and the new cell plate is beginning to mature. These walls are rich in plasmodesmata and we show that they are the regions where the longitudinal actin cables appear to attach. Myosin VIII appears to be localized in these plasmodesmata and we suggest that this protein is involved in maturation of the cell plate and the re-establishment of cytoplasmic actin cables at sites of intercellular communication.

Arabidopsis↗
PubMed1994

Therapy with refugee families: what is a "good" conversation?

This article addresses the question of what is a "good" conversation by analyzing "poor" conversations. During a project on family therapy with refugee families, we often experienced what we labeled as "poor" conversations. We present examples of a variety of such conversations, which we then analyze with reference to therapeutic maps and central concerns of the therapists. We describe four patterns of therapist/client relationships that emerged from this analysis. The main focus of our discussion is to clarify when "poor" conversations may be an important part of the therapeutic process, and when and how they should be avoided. We believe that the issues we raise are central to therapeutic work in general and not just to therapy with refugee families.

Acculturation↗
PubMed1992

[The visibility of a central venous catheter using digital luminescence radiography in intensive care radiology].

The aim of the following study was to assess the impact of dose alterations on the detection of catheters. We compared the performance of well-exposed conventional and digital portable chest radiographs in the detection of thin catheters and tested the influences of dose alterations. Portable chest radiographs of 20 patients were obtained with conventional film/screen (FR) and with storage phosphors at 50% (SRL), 100% (SRN), and 250% (SRH) of the conventionally required exposure dose. The region of the mediastinum was subdivided into an average of 18 fields, 50% of which were superimposed with thin catheter segments. ROC analysis of 11,600 observations by 8 readers found only SRH equivalent to FR in catheter visualisation. Performance decreased significantly with SRN and SRL. Detection of low contrast catheters was found to be significantly decreased in storage phosphor radiographs obtained with standard exposure dose. A dose reduction is not feasible with current equipment if performance equivalent to conventional radiography is to be achieved.

Catheterization, Central Venous↗
PubMed1992

Impact of hard-copy size on observer performance in digital chest radiography.

To determine the impact of reduced hard-copy size on diagnostic performance of digital radiography, screen-film chest radiographs were compared with isodose digital storage phosphor radiographs in the detection of simulated nodules, fine pulmonary lines, and micronodular opacities superimposed on the chests of 10 healthy volunteers. Digital radiographs were laser-printed in a full-size conventional format and in image lengths of two-thirds, one-half, and five-elevenths of the conventional format. Eighteen thousand observations by eight radiologists were analyzed by use of receiver operating characteristics. The detectability of lines and micronodular opacities decreased with declining image format size. In the detection of micronodular opacities, only the nearly full-size digital images were equivalent to conventional images. In the detection of linear opacities, reduction of image length by one-half or more reduced performance (analysis of variance, P less than .05). Only for the detection of nodules was no major difference found.

Humans↗
PubMed1992

[Chemoembolization of hepatocellular carcinoma in cases of isolated liver involvement].

Chemoembolization is an effective treatment for hepatocellular carcinoma, giving results equally as good as surgical therapy for T2 tumours. Survival can be prolonged and side-effects can be reduced by combining Lipiodol and Gelfoam for chemoembolization, employing a modified technique, with repeated procedures, and using appropriate follow-up treatment. The toxicity of the procedure is acceptable, but it requires supportive therapy necessitating an intense interdisciplinary co-operation.

Aged↗
PubMed1991

[Digital radiography: optimization of chest radiographs using a modified exposure control].

Phototiming over the lung fields frequently compromises the signal-to-noise ratio available in the mediastinal and diaphragmatic regions of the chest. A moderate dose increase would be justified if a significant improvement in diagnostic performance could be achieved. We compared the impact of mediastinal phototiming (150 kVp, 150 cm FFD, 1.0 mm focus, 12:1 grid [higher kVp chosen to minimize dose increase]) to standard lungfield phototiming (125 kVp, 150 cm FFD, 1.0 mm focus, 12:1 grid) on the detectability of simulated pulmonary nodules (wax, 0.5-2.5 cm in diameter) superimposed on human volunteers in storage phosphor radiographs (1744 x 2144 pixels, 10 bit). ROC analysis of 1920 observations by 8 readers showed a significantly higher (p less than 0.03) detectability of simulated pulmonary nodules with mediastinal phototiming (ROC area = 0.89) than standard lungfield phototiming (ROC area = 0.84).

Humans↗
PubMed1991

[Radiological follow-up of anastomotic insufficiency following partial esophageal resections or gastrectomies. The effects of barium-containing contrast media].

Fistulae after abdomino-thoracic operations are usually treated conservatively because of the high complication rate of repeated surgery. If the anastomoses function adequately, healing usually occurs spontaneously after four to six weeks. Amongst 271 patients with intrathoracic oesophago-gastric or oesophago-jejunal anastomoses, entero-cutaneous fistulae occurred 29 times. Extension of the fistula into the pleura or peritoneum was first excluded by using an absorbable contrast medium and then a barium contrast examination was carried out. Thoracic fistulae closed, on average, after 21.8 days and fistulae in the upper abdomen after 20.3 days. Barium sulphate stimulates granulation tissue in the fistula and therefore leads to more rapid obliteration. This improves the quality of the patient's life and reduced the time the patient has to spend in hospital. There were no local or systematic complications.

Adult↗
PubMed1991

[Sinus tarsi and canalis tarsi syndromes. A post-traumatic entity].

The posttraumatic sinus tarsi syndrome is a clinical entity induced by supination trauma of the hindfoot. In pathomorphological terms this is due neither to a ligament rupture nor to an osteochondral lesion. Clinically, local pain in the sinus tarsi is associated with pain during supination or pronation, pain during walking, especially on uneven ground, and "giving way" without signs of mechanical instability. A more severe variant of this syndrome, in which the patient complains of pain on the medial aspect of the hindfoot in conjunction with the typical pain of the sinus tarsi syndrome is described. This medial symptom complex has been identified as the "canalis tarsi syndrome". Injection of a steroid and local anaesthetic agent into the tarsal sinus or tarsal canal will relieve the pain if the underlying pathology is that of a tarsi syndrome, depending on which side the injection is given. An arthrogram of the subtalar joint in a patient with a confirmed sinus tarsi syndrome demonstrates a sac-like anterior bulge of the capsule. Performed on a non-pathologic tarsal sinus, this procedure would demonstrate a corrugated appearance of the capsule anteriorly, without this anterior protrusion. At the Medical School in Hanover, 95 patients with a sinus tarsi syndrome were assessed between 1981 and 1989. In all patients a conservative regimen of repeated injections (6 or fewer) of a steroid and local anaesthetic agent into the tarsal sinus was instituted. In addition, 3 of these patients were identified as having a canalis tarsi syndrome, and injections were simultaneously given into their tarsal canals.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

[Digital projection radiography].

Several hundred storage phosphor digital projection radiography (DR) systems are in operation in many parts of the world in experimental and clinical settings. They are used clinically for almost all projection radiographic studies except mammography. An overview is given of the experimental and clinical results achieved so far. Image post-processing has yet to meet the initial expectations. The average image quality will certainly improve with automatic brightness control. Edge enhancement should be performed in selected applications only. A true increase in diagnostic information probably cannot be expected except with dual energy techniques. Dose reductions are possible only in those studies in which the specific imaging task permits a decrease in signal-to-noise ratio.

Humans↗
PubMed1991

[Destructive non-infectious spondylopathy during hemodialysis].

Improvement of long-term treatment with hemodialysis requires an optimized radiological differential diagnosis of bone changes associated with long-term hemodialysis. 85 patients with chronic renal failure on maintenance hemodialysis were examined. In a conventional radiographic skeletal survey of the whole spine, 22 patients (26%) had involved intervertebral discs. The site of predilection was the cervical spine followed by the lumbar spine; oligosegmental involvement was seen in nine patients. Eighteen patients with destructive non-infectious spondyloarthropahy had juxtaarticular cystic bony changes associated with the hip, shoulder and wrist. Bone biopsy in eight patients revealed amyloid as content of these cysts. The interrelation between the duration of preterminal and terminal renal failure on one hand and destructive bone changes in the spine and cysts on the other hand seems to point to destructive spondyloarthropathy as an important complication of renal insufficiency and dialysis.

Adult↗
PubMed1990

Reflections during a study on family therapy with drug addicts.

This article presents ideas and reflections emerging during a project on family therapy with drug abusers. Initially inspired by the writings of Stanton and Todd on the subject, the project developed into a recursive and self-reflective process, characterized by increasing doubts about the usefulness of categorization of families, of pre-planning therapy, and of the therapist as an "expert." The limitations of approaches that emphasize the importance of understanding the family structure as the basis for changing it are discussed, particularly with respect to how they decrease therapist flexibility and may block the family's finding their own solution. Alternative approaches to practice and research are also discussed, bearing on ideas particularly formulated by theoreticians and practitioners inspired by second-order cybernetics.

Adolescent↗