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Biomedical subjects

A Winter

Publications and source records attributed to A Winter.

At least 55 records · Page 3Linked to original sources
PubMed1996

Gangliosides in phospholipid bilayer membranes: interaction with tetanus toxin.

The interaction between tetanus toxin and its fragments with gangliosides and negatively charged phosphatidylglycerols has been studied in phosphatidylcholine host membranes by protein circular dichroism measurement, calorimetry to determine lipid phase transitions, and by fluorescence spectroscopy to follow the toxin-induced pore formation by measuring the release of intravesicular entrapped dye. CD-spectroscopic secondary structure analysis showed conformational change of the toxin only in the presence of GT1b clearly demonstrating the involvement of the ganglioside headgroups for this lipid-protein-interaction. In a dot-blot analysis we showed that fragment C binds to GT1b in reconstituted vesicles and that this fragment is then accessible to a fragment C specific antibody which is only possible if fragment C is exposed at least partially on the surface of the vesicle. Our calorimetric study demonstrates the preferential binding of tetanus toxin to ganglioside GT1b. However, this protein is also able to bind to other gangliosides and also to negatively charged phospholipids causing phase separation due to electrostatic interaction. Since tetanus toxin preferentially binds short chain phosphatidylglycerol, we conclude that the protein adopts lipids with respect to charge, head group structure and chain length from the bulk phase. One consequence of this lipid-protein interaction is the ability of tetanus toxin to permeabilize lipid vesicles. Pore formation is favoured in the presence of GT1b in phosphatidylcholine membranes but only at a sufficiently high enough ganglioside content. Gangliosides others than GT1b are less effective in pore formation. In the presence of negatively charged phosphatidylglycerol tetanus toxin causes a dye release which in contrast to GT1b-containing vesicles is not saturable. We conclude that tetanus toxin acts in combination with a given number of GT1b molecules. Twenty ganglioside molecules are found to be necessary to form the stable pore. Other negatively charged lipids also cause the toxin to intercalate into the membrane but in this case the release velocity is determined by the formation of membrane defects.

Circular Dichroism↗
PubMed1996

Calcium acetate versus calcium carbonate as oral phosphate binder in pediatric and adolescent hemodialysis patients.

Calcium carbonate is widely used as an oral phosphorus binder to control hyperphosphatemia in children on maintenance hemodialysis. Intestinal calcium absorption may induce hypercalcemia, particularly if calcitriol is given simultaneously. In adults, calcium acetate binds phosphorus more effectively than calcium carbonate, while reducing the frequency of hypercalcemic events. We therefore compared calcium acetate with calcium carbonate in nine pediatric patients on long-term maintenance hemodialysis. Following a 1-week withdrawal of phosphorus binders, calcium carbonate was administered for 7 weeks; after a second withdrawal, calcium acetate was given for another 7 weeks. All patients received calcitriol regularly. Both agents lowered the serum phosphorus concentration significantly (calcium carbonate 5.7 +/- 1.4 vs. 7.7 +/- 2.1 mg/ dl, P < 0.005; calcium acetate 5.8 +/- 1.4 vs. 7.8 +/- 2.0 mg/dl, P < 0.005). Significantly less elementary calcium was ingested with calcium acetate than with calcium carbonate: 750 (375-1,500) vs. 1,200 (0-3,000) mg calcium/day, P < 0.0001. Wit calcium carbonate serum calcium increased significantly. The number of episodes of hyperphosphatemia or hypercalcemia did not differ between treatments. Intact plasma parathyroid hormone (PTH) decreased significantly with both phosphate binders, and serum 25-hydroxyvitamin D3 increased. There was a close relationship between serum phosphorus and PTH in prepubertal but not in pubertal patients. We conclude that hyperphosphatemia can be controlled effectively by both calcium acetate and calcium carbonate in pediatric hemodialysis patients. The oral load of elementary calcium is reduced significantly by binding phosphorus with calcium acetate instead of calcium carbonate; nevertheless, hypercalcemic episodes remain equally frequent with both phosphate binders.

Acetic Acid↗
PubMed1996

Knowledge retrieval as one type of knowledge-based decision support in medicine: results of an evaluation study.

We report on a prospective, prolective observational study, supplying information on how physicians and other health care professionals retrieve medical knowledge on-line within the Heidelberg University Hospital information system. Within this hospital information system, on-line access to medical knowledge has been realised by installing a medical knowledge server in the range of about 24 GB and by providing access to it by health care professional workstations in wards, physicians' rooms, etc. During the study, we observed about 96 accesses per working day. The main group of health care professionals retrieving medical knowledge were physicians and medical students. Primary reasons for its utilisation were identified as support for the users' scientific work (50%), own clinical cases (19%), general medical problems (14%) and current clinical problems (13%). Health care professionals had accesses to medical knowledge bases such as MEDLINE (79%), drug bases ('Rote Liste', 6%), and to electronic text books and knowledge base systems as well. Sixty-five percent of accesses to medical knowledge were judged to be successful. In our opinion, medical knowledge retrieval can serve as a first step towards knowledge processing in medicine. We point out the consequences for the management of hospital information systems in order to provide the prerequisites for such a type of knowledge retrieval.

Computer Systems↗
PubMed1996

Health professional workstations and their integration in a hospital information system: the pragmatic approach MEDIAS.

Within the daily workload at a ward there is a considerable amount of information processing. It is the task of a systematic management of hospital information systems to provide health professionals with the right information in the right place at the right time. This paper deals with the consequences for the management of hospital information systems if health professional workstations are introduced as a means for this information logistic and with the experiences gained in the Heidelberg University Hospital. Health professional workstations are formally defined in the context of a three level graph-based model of hospital information systems. It is found that health professional workstations have communication needs not only on the physical level of computer systems in the hospital information system but also on the logical tool level, which is the level of application systems. On this level communication servers or brokers are of considerable importance. In Heidelberg there are about 200 health professional workstations (MEDIAS) in routine use.

Computer Communication Networks↗
PubMed1995

Processing of prodynorphin-derived peptides in striatal extracts. Identification by electrospray ionization mass spectrometry linked to size-exclusion chromatography.

Proteolytic processing of prodynorphin-derived peptides in rat brain was studied with the help of high performance size exclusion chromatography (SEC) connected to electrospray ionization mass spectrometry. Extracts from rat striatum were incubated with individual synthetic dynorphin peptides. Dynorphin A was the most resistant to proteolytic cleavage, converting slowly to Leu-enkephalin (0.3 pmol/min), whereas dynorphin B was processed to this pentapeptide at a 10(4)-fold higher rate. Minor cleavage was also observed between Arg6-Arg7. Alphaneoendorphin was also rapidly metabolized to Leu-enkephalin (6 nmol/min) and, to a lesser extent, to Leu-enkephalinArg6. This new strategy for studying peptidases can easily be adapted to identification of components present in body fluids.

Animals↗
PubMed1995

A three-level graph-based model for the management of hospital information systems.

Information processing in hospitals, especially in university hospitals, is currently faced with two major issues: low-cost hardware and progress in networking technology leads to a further decentralization of computing capacity, due to the increasing need for information processing in hospitals and due to economic restrictions, it is necessary to use commercial software products. This leads to heterogeneous hospital information systems using a variety of software and hardware products, and to a stronger demand for integrating these products and, in general, for a dedicated methodology for the management of hospital information systems to support patient care and medical research. We present a three-level graph-based model (3LGM) to support the systematic management of hospital information systems. 3LGM can serve as a basis for assessing the quality of information processing in hospitals. 3LGM distinguishes between a procedural level for describing the information procedures (and their information interchange) of a hospital information system and thus its functionality, a logical too level, focusing on application systems and communication links, and a physical tool level with physical subsystems (e.g., computer systems) and data transmission. The examples that are presented have been taken from the Heidelberg University Hospital Information System.

Computer Graphics↗
PubMed1995

[Wound management after wisdom tooth osteotomy].

Closure and dressing techniques in wound treatment after surgical removal of the mandibular third molars were compared. Large abscesses were found after third molar removal in 8 percent. An extraoral incision was made in 58 percent of these cases. On the other side, in a group of 1189 third molar removals treated by a gauze strip no abscess was observed. In a further investigation the subjective disturbance of patients treated with a dressed gauze were the slightest. Also, the dressing technique in the treatment after third molar removal could decrease the number of postoperative infections.

Bandages↗
PubMed1995

An integrated approach for mobile information processing in hospitals.

Computer-based mobile information processing in hospitals is at a turning point of becoming a substantial and integral part of hospital information systems. Its necessity and potential require a comprehensive systematic approach to support the needs of health care professionals and thus to contribute to high quality patient care and medical research. From the authors' point of view, standardized digital documents could become an appropriate basis for distributed mobile information processing in hospitals. An architecture for the integrated co-operative use of conventional, stationary, and mobile information tools is a major research topic at Heidelberg University. The objective of this paper is to present a departmental prototype design to establish mobile information processing as an integral part of hospital information systems through the use of standardized digital documents.

Computer Communication Networks↗
PubMed1995

Digital optical archiving of medical records in hospital information systems--a practical approach towards the computer-based patient record?

The large number of inpatients and outpatients in university hospitals leads to high costs of medical documentation and to an increasing number of medical documents. Due to legal regulations, these medical records have to be stored for 30 years. This implies spatial, organizational, and economical problems. At present, conventional archiving in hospitals often does not satisfy the need to make medical records available for health-care professionals in a systematic and timely manner. From 1989 to 1993 a pilot study on "digital optical archiving of medical records" was carried out at Heidelberg University Hospital. The study has shown the feasibility of digital optical archiving in hospital s if done under certain conditions. In 1995, Heidelberg University Hospital adopted a procedure for "digital optical archiving of medical records". The digital optical archive will first be filled with the medical records of the department of neurosurgery and the endoscopic and echographic images and reports of the department of internal medicine. It is to be expected that this procedure will gradually lead to an integrated functionality on health-care professional workstations, to a hospital-wide use of an electronic patient record, and to media-independent document management systems. The paper focuses on the potentials of digital optical archiving as an integral part of hospital information systems, and on the requirements for the systematic managements of hospital information systems with respect to digital optical archives.

Archives↗
PubMed1994

Re-replication of SV40 minichromosomes is inhibited at the stage of chain elongation.

The template activities of protein-free SV40 DNA and SV40 minichromosomes for DNA re-replication are compared in in vitro replication assays. Density substitution experiments and two-dimensional gel electrophoresis show that protein-free DNA can replicate for at least two cycles whereas salt-treated minichromosomes replicate only once. Re-replication of minichromosomes is blocked at the stage of replicative chain elongation suggesting that replicatively assembled chromatin has structural features that prevent a second round of replication.

Chromosomes↗
PubMed1994

[Intrauterine growth in full-term twins without risk factors].

Twins are analysed according to the intrauterine growth curve constructed for single fetus. The relationship of twins with length, weight, head circumference and the weight length-index is studied. Twins over 36 weeks gestation age, without maternal or fetal pathologies were selected. It is concluded the twins pregnancy "per se" constitutes on its own, a risk factor regarding the intrauterine growth curve, particularly in relation with the weight curve.

Birth Weight↗
PubMed1992

Ciguatera toxins in the food chain revealed by stable isotopes.

The stable carbon and nitrogen isotope contents of the meat tissues of 27 identifiable fish found in the gut contents of 70 ciguatoxic and non-ciguatoxic barracuda caught along the southwest coast of Puerto Rico have been analyzed. The isotope ratios of those fish found in the stomach contents of ciguatoxic barracuda were significantly different than ratios determined in those fish found in the stomachs of non-ciguatoxic barracuda. The isotope ratios of the toxic dinoflagellate Ostreopsis lenticularis, a presumed vector of ciguatera in the Caribbean were found to be extremely light, particularly for nitrogen. The lightened nitrogen ratios of the herbivore (Doctorfish) and carnivore (Squirrelfish) fishes found in the stomach contents of ciguatoxic barracuda suggest that the dinoflagellate was in the food chain of these barracuda. Results indicate that the trophic pathway of ciguatoxins through the marine food chain from the presumed primary trophic level (dinoflagellates/bacteria) to ciguatoxic barracuda appears to be different than the pathway to non-toxic barracuda. Stable isotope ratios may be a very useful tool for tracing ciguatoxins in the food chain and the identification of ciguatoxic fish.

Animals↗
PubMed1992

[Neonatal autoimmune purpura: laboratory study of 5 cases].

Maternal alloimmunization against fetal platelets can cause fetal and neonatal thrombocytopenia. We report our experience in the study of five cases with severe neonatal-thrombocytopenia. Using an ELISA with antigen capture and other serologic tests on platelets, we investigated the sera of the five mothers. Sera from four mothers contained a platelet-specific alloantibody, anti-HPA-1a (PlA1) whereas the platelets typed as HPA-1b/b. In one case despite extensive serological investigation and clinically unequivocal diagnosis of AINT, no antibodies were demonstrated. The use of monoclonal antibodies for antigen immobilization, showed to be a reliable and sensitive test for the detection and identification of platelet antibodies in AINT. These techniques could also be used in the follow-up of patients at risk (e.g. pregnant HPA-1b/b women) and in the screening of blood donors lacking of certain antigens, whose platelets are collected to be transfused in patients with platelet-specific antibodies.

Antigens, Human Platelet↗