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Biomedical subjects

A Seitz

Publications and source records attributed to A Seitz.

At least 37 records · Page 2Linked to original sources
PubMed2001

The use of Markovian metapopulation models: a comparison of three methods reducing the dimensionality of transition matrices.

The use of Markovian models is an established way for deriving the complete distribution of the size of a population and the probability of extinction. However, computationally impractical transition matrices frequently result if this mathematical approach is applied to natural populations. Binning, or aggregating population sizes, has been used to permit a reduction in the dimensionality of matrices. Here, we present three deterministic binning methods and study the errors due to binning for a metapopulation model. Our results indicate that estimation errors of the investigated methods are not consistent and one cannot make generalizations about the quality of a method. For some compared output variables of populations studied, binning methods that caused a strong reduction in dimensionality of matrices resulted in better estimations than methods that produced a weaker reduction. The main problem with deterministic binning methods is that they do not properly take into account the stochastic population process itself. Straightforward usage of binning methods may lead to substantial errors in population-dynamical predictions.

Markov Chains↗
PubMed2001

Enzymatic cross-linking of purple membranes catalyzed by bacterial transglutaminase.

It was found that bacterial transglutaminase (TGase) facilitates selective cross-linking of bacteriorhodopsin (BR) in purple membrane (PM) form under mild conditions. Fluorescent probes were used to detect that the membrane protein BR may act as a glutamine donor as well as a lysine donor for TGase. The binding sites were determined to be Gln-3 as the reactive glutamine, and Lys-129 is the corresponding lysine residue. Upon incubation of PM with TGase, cross-linking of PM patches can be achieved without an additional spacer molecule. To our knowledge, this is the first time that an intermembrane cross-linking of membrane-bound proteins is reported. Furthermore, this finding may provide the ability to achieve covalent linkage of complete purple membrane patches to synthetic polymers.

Bacteriorhodopsins↗
PubMed2001

Genetic interchange of Dreissena polymorpha populations across a canal.

The zebra mussel Dreissena polymorpha, has been invading western Central Europe since the early 19th century, coming from the Pontocaspian by two routes, each interconnected by large rivers and canals constructed at that time. By 1992 these two invasion populations had been given the opportunity to mix extensively across the newly built Main-Danube canal. Different hypotheses about the dynamics of genetic interchange have been postulated, ranging from a stable intergradation zone to complete mixing. We analysed the allozyme variation at nine loci in 14 or 17 populations, respectively, across the canal on two occasions: 2(1/2) years and 4(1/2) years after the opening. At the first sampling a strong genetic differentiation at three loci was found between the two invasion lines. This differentiation declined during the two-year period. The main effect was an assimilation of the Main populations according to the gene frequencies of the Danube populations, which suggest a swamping of the Main populations by Danube-type larvae. This inference is congruent with the overall water flow regime across the canal, i.e. active pumping from the Danube into the Main drainage system. The observed interchange processes allow some inferences to be made about the selective significance of the highly heterozygous allozyme loci in D. polymorpha.

Animals↗
PubMed2001

[Canavan disease].

Explore the source record for details and available documents.

Aspartic Acid↗
PubMed2001

"Docs 'n drugs--the virtual polyclinic": an intelligent tutoring system for web-based and case-oriented training in medicine.

Since the beginning of the year 2000 medical students of the University of Ulm are working in their curriculum with the web-based and case-oriented tutoring system "Docs 'n Drugs - The Virtual Polyclinic". The system consists of different subsystems and services. One subsystem is the Training System. It is based on three models: the Tutoring Process Model, the Case Knowledge Model and the Medical Knowledge Model. They describe the tutoring process as a series of nodes and steps, depict the structure of the medical cases, and provide the medical knowledge respectively. Case knowledge and medical knowledge form the expert knowledge of the medical domain. Together with the tutoring process, they build the basis for automatic intelligent tutoring. After giving a deeper insight into the system architecture and the training case structure, an informal evaluation shows a first feedback of the learners.

Clinical Medicine↗
PubMed2000

Recovery of cognitive function after remifentanil-propofol anesthesia: a comparison with desflurane and sevoflurane anesthesia.

UNLABELLED: We compared the recovery characteristics of remifentanil, desflurane, and sevoflurane when used for anesthesia in elective operative procedures. Sixty ASA physical status I and II patients, aged 18-65 yr, were randomly assigned to receive remifentanil-propofol, desflurane-N2O, or sevoflurane-N2O anesthesia. Before the induction of anesthesia, the patients of the desflurane and sevoflurane groups received fentanyl 2 microg/kg. In all groups, anesthesia was induced with propofol and maintained either with remifentanil 0.25 microg x kg(-1) x min(-1), desflurane, or sevoflurane 0.85 MAC with 65% nitrous oxide in oxygen. Anesthetics were titrated to achieve an adequate level of surgical anesthesia and to maintain mean arterial pressure within 20% of baseline values. Early recovery times and a modified Aldrete Recovery Score > 9 were recorded. Trieger Dot Test and Digit Substitution Test (DSST) were performed the day before surgery and in the postanesthesia care unit to evaluate intermediate recovery. The remifentanil-propofol group had a significantly faster emergence than desflurane or sevoflurane, with no difference between both inhaled anesthetics. Thirty min after anesthesia administration, patients in the remifentanil-propofol and in the desflurane groups gave significantly more correct responses in the DSST compared with sevoflurane (remifentanil 87%, desflurane 83%, sevoflurane 56%), the impairment in the sevoflurane patients corresponding to the effects of a blood alcohol level of approximately 0.1% and, thus, being of clinical importance. Ninety minutes after anesthesia administration, no significant difference could be demonstrated among the groups in the DSST scores. Emergence and return of cognitive function was significantly faster after remifentanil-propofol compared with desflurane and sevoflurane up to 60 min after anesthesia administration. IMPLICATIONS: We compared awakening and intermediate recovery times after remifentanil-propofol anesthesia to desflurane-N2O and sevoflurane-N2O anesthesia. Emergence and return of cognitive function was significantly faster after remifentanil-propofol compared with desflurane and sevoflurane up to 60 min after anesthesia administration.

Adult↗
PubMed2000

A flexible architecture for constructing and executing tutoring processes.

The tutoring process of conventional case-oriented medical training systems can be characterised as either guided or unguided. In contrast to that, the aim of the system "Docs'n Drugs" is to distinguish between different levels of guidance. The author can realise the tutoring case as a guided, a half guided or an unguided tutoring process. The system architecture distinguishes between an authoring system and a tutoring system. Fundaments of these are the tutoring process model and the case data model. This structure allows the reuse of elements of existing tutoring cases. The tutoring cases can be realised in different languages, e.g. German and English.

Computer-Assisted Instruction↗
PubMed1999

[Skull and brain injuries in children].

Our contribution reviews the diagnostic algorithm of head injuries in children. According to the Heidelberg consensus on head injury, patients should be divided into three risk groups. In low-risk patients clinical observation is the method of choice and radiological examinations are usually unnecessary. Patients at medium risk should be observed carefully. Sometimes neurosurgical consultation or CT is necessary. High risk patients in most instances need CT and neurosurgical consultation. Skull X-ray is helpful only in selected cases. A simple fracture as demonstrated by skull X-ray has no therapeutic consequence. However, normal findings in skull X-ray do not exclude intracranial injury. CT is the method of choice to detect intracranial hemorrhage, epi- or subdural hematoma and cerebral contusion. If patients present with severe clinical deficits, CT allows characterization of lesions and initiation of specific therapy.

Brain Injuries↗
PubMed1999

Case-based prediction in experimental medical studies.

Case-based approaches predict the behaviour of dynamic systems by analysing a given experimental setting in the context of others. To select similar cases and to control adaptation of cases, they employ general knowledge. If that is neither available nor inductively derivable, the knowledge implicit in cases can be utilized for a case-based ranking and adaptation of similar cases. We introduce the system OASES and its application to medical experimental studies to demonstrate this approach.

Animals↗
PubMed1999

The anatomy of the angular branch of the thoracodorsal artery.

This study reports an anatomical investigation of the angular branch of the thoracodorsal artery, which can be used in reconstructive surgery to serve as a pedicle for gaining osseous material from the scapula. The study was performed on 135 samples and topography and morphometry of the vessel were investigated. It was found that this artery has five main types of origin. It courses in the fascial gliding layer between the serratus muscle, and the teres major and subscapular muscle to the inferior angle of the scapula. There it provides the bone with blood through periostal branches as part of the arterial rete on the costal and dorsal side of the scapula. The mean length of the angular branch and the thoracodorsal artery together was 148 mm, and when also adding the subscapular artery the overall length became 167 mm. It was found that the length of a pedicle consisting of the angular branch and the thoracodorsal artery is determined by the difference in origin of the vessels with minor influences of the body size. The internal diameters of unfilled fixated vessels measured 3.06 mm for the subscapular, 1.77 mm for the circumflex scapular, 1.30 mm for the thoracodorsal and 0. 64 mm for the angular branch. The exact knowledge of the microanatomy in this area is necessary to be able to use the osseous free flap more selectively and have less traumatization in the donor area.

Aged↗
PubMed1998

The significance of relatedness and gene flow on population genetic structure in the®subsocial spider Eresus cinnaberinus (Araneae: Eresidae)

Interdemic selection, inbreeding and highly structured populations have been invoked to explain the evolution of cooperative social behaviour in the otherwise solitary and cannibalistic spiders. The family Eresidae consists of species ranging from solitary and intermediate subsocial to species exhibiting fully cooperative social behaviour. In this study we, in a hierarchical analysis, investigated relatedness of putative family clusters, inbreeding and population genetic structure of the subsocial spider Eresus cinnaberinus. Five hierarchical levels of investigation ranging from large scale genetic structure (distances of 250 and 50 km level 1 and 2) over microgeographic structure (20 km2 and 4 km2, level 3 and 4) to a single hill transect of 200 m (level 5) were performed. The purpose of level 5 was two-fold: (1) to investigate the relatedness of putative family groups, and (2) to evaluate the influence of both family living and sampling design on higher level estimates. Relatedness estimates of putative family groups showed an average relatedness of R=0.26. There was no indication of inbreeding. In contrast to social spiders, genetic variation was abundant, Heapproximately0.10. The population genetic structure was intermediate between social and asocial spiders. Genetic variance increased continually across hierarchical levels. Family structured neighbourhoods biased differentiation estimates among level 5 samples (FST=0.04) and level 3 and 4 samples (0.07 0, was caused by disjunct sampling from separate neighbourhoods. Larger scale samples were highly differentiated 0.12<FST<0.26, depending on level and sampling design. Due to a distance effect family living did not influence estimates of the higher level 1. Although the dispersing sex among social spiders and the subsocial E. cinnebarinus differ, females versus males, female behaviour of both sociality classes lead to high genetic variance.Copyright 1998 The Linnean Society of London

Journal Article↗
PubMed1997

[Abomasal ulcers in calves: clinical investigations and experiences].

Observations and experiences as well as results of clinical investigations in 364 calves with clinically apparent abomasal ulcers (bleeding 28, deep 37, perforating 299) are communicated. The anamnestic data, evaluated systematically, allow to conclude, that influences of the feeding regime, in particular faults during the early weaning period, play an important role in the multifactorial etiology. Furthermore, symptoms, diagnosis and differential diagnosis as well as treatment and prevention are described. The various localizations (and ways) of perforating abomasal ulcers are demonstrated by schematic representations and by the respective findings at operation or at necropsy.

Abomasum↗
PubMed1995

Evaluation of liver function tests in neonatal calves.

OBJECTIVE: To evaluate the efficacy of tests for hepatic disease in young calves. DESIGN: Prospective case-control study. ANIMALS: 28 clinically normal calves and 47 calves with histologically proven hepatic disease. PROCEDURE: Liver function tests and serum activity of liver-derived enzymes were determined on 28 clinically normal calves at birth and at 2 weeks of age. These values were compared with the results from 47 calves with hepatic disease verified by histologic examination. Upper limit of confidence interval was determined for the results on the clinically normal calves, and Student's t-test was used to identify significant differences in the data from calves of various age-groups. RESULTS: None of the results of the common tests for liver damage or function (measurement of bilirubin, gamma-glutamyltransferase, glutamate dehydrogenase [GMD], alkaline phosphatase, L-lactate dehydrogenase, aspartate transaminase, or alanine transaminase) were clinically useful when used alone for detection of hepatic disease in calves less than 6 weeks old. Sensitivity of gamma-glutamyltransferase, GMD, aspartate transaminase, and alkaline phosphatase as indicators of hepatic disease in this population of calves was 0, 59, 80, and 9%, respectively. Direct bilirubin (sensitivity, 87%) was more sensitive than total bilirubin (sensitivity, 66%). Serum enzyme activity of most enzymes (P < 0.01), total bilirubin concentration (P < 0.001), and sulfobromophthalein sodium clearance half-life were significantly higher (P < 0.001) in newborn calves than in 2-week-old calves. CLINICAL IMPLICATIONS: Clinical findings that indicate hepatic disease in calves that are less than 6 weeks old could be confirmed by measurement of serum activity of GMD or concentrations of total serum bile acids or direct bilirubin. Percutaneous liver biopsy may still be needed and may provide the most information.

Animals↗
PubMed1993

Paternity testing of endangered species of birds by DNA fingerprinting with non-radioactive labelled oligonucleotide probes.

In the last years, DNA fingerprinting became the most powerful tool for identification and paternity testing in man. The success of this method encouraged the German Federal Ministry of Environment, Natural Protection and Reactor Safety to apply DNA fingerprinting in the field of protection of endangered species of birds, such as birds of prey or parrots. In the last three years, we received more than 400 blood and tissue samples of 23 species of birds of prey or parrots, most of them obtained by confiscation, to establish paternity and legal breeding success. We used digoxigenated oligonucleotide probes, mainly (GGAT)4 and (GACA)4 for hybridization. In most cases of confiscated families of birds, paternity testing showed exclusions of nestlings.

Animal Husbandry↗