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Biomedical subjects

J Sauer

Publications and source records attributed to J Sauer.

At least 19 recordsLinked to original sources
PubMed2006

Evaluating an optimal gastric closure method for transgastric surgery.

BACKGROUND: The transgastric approach is currently being studied as a potentially less invasive alternative to conventional laparoscopy for intra-abdominal surgery. A major obstacle to overcome is the closure of the transgastric incision in a rapid, reproducible, and safe manner. The effectiveness of various techniques for gastrotomy closure were compared by assessing leak pressures in an ex vivo porcine stomach model. METHODS: Whole stomachs from adult white pigs were suspended in a Plexiglas box to facilitate endoscopic technique. Standard gastrotomies were made by needle knife incision and dilation with a controlled radial expansion (CRE) balloon. The first arm used standard QuickClips; the second, a prototype device developed by LSI Solutions; the third, hand-sewn by a senior surgeon; the final, a control with open gastrotomy. Five stomachs were tested per study arm. After closure, each stomach was inflated by an automated pressure gauge. The pressures to achieve air leakage and liquid leakage were recorded. RESULTS: The unclosed controls demonstrated air leakage at a median pressure of 15 mmHg, representing baseline system resistance. The QuickClip closures leaked air at a median pressure of 33 mmHg. The prototype gastrotomy device yielded the highest median air leak pressure of 85 mmHg while dramatically diminishing time for incision and gastrotomy closure to approximately 5 min. The hand-sewn closures leaked air at a median pressure of 47 mmHg. Using Kruskal-Wallis statistical analysis, the comparisons were significant (p = 0.0019). Post hoc paired comparisons using MULTTEST procedure with both Bonferroni and bootstrap adjustments revealed that the difference between prototype and clips was significant; prototype versus hand-sewn was not. Liquid-leak pressures produced similar results. CONCLUSIONS: The prototype device decreases procedure time and yields leak-resistant gastrotomy closures that are superior to clips and rival hand-sewn interrupted stitches.

Animals↗
PubMed2006

Isomorphous substitution in bimetallic oxide clusters.

The geometric and electronic structure of bimetallic oxide clusters is studied as a function of their composition with gas phase vibrational spectroscopy. Infrared multiple photon dissociation spectra of titanium-vanadium oxide cluster anions are measured in the 500 to 1200 wave number range and assigned on the basis of harmonic frequencies calculated using density functional theory. Singly substituted (V(2)O(5))(n-1)(VTiO(5))(-) (n=2-4) cluster anions are shown to form polyhedral caged structures similar to those predicted for their isoelectronic counterparts, the neutral (V(2)O(5))(n) clusters. Upon systematic exchange of V by Ti atoms in V(4-n)Ti(n)O(-)(10) (n=1-4), the structure does not change. The stress induced by the isomorphous substitution results in an increased number of unpaired electrons (n-1) for the Ti-rich systems, leading to a quartet ground state for Ti(4)O(-)(10).

Journal Article↗
PubMed2006

Interaction of SO3 with c-ZrO2(111) films on Pt(111).

Single-crystalline sulfated c-ZrO2(111) films of the cubic (c) type have been prepared by reactive deposition of Zr onto Pt(111) in an O2 atmosphere and subsequent exposition to a SO3 atmosphere. The morphology, atomic structure, and composition have been examined by scanning tunneling microscopy, low-energy electron diffraction (LEED), Auger electron spectroscopy, and density functional theory (DFT) calculations. The clean c-ZrO2(111) films display a (2x2) surface structure. During SO3 exposure at room temperature, a clear (radical3xradical3)R30 degrees structure develops. At about 700 K, the SO3-induced (radical3xradical3)R30 degrees structure disappears and the bright (2x2) LEED pattern of the clean ZrO2 films reappears. The energies of plausible c-ZrO2(111)/SO3 structures have been examined by DFT. The (radical3xradical3)R30 degrees structure found in the experiments turned out to be the most stable one for temperatures below 700 K. At temperatures around 700 K, a disordered low coverage structure may exist, which can not be observed by conventional LEED. A comparison of cubic zirconia surfaces with the alternative tetragonal system yields similar results for the SO3 adsorption in the DFT calculations and shows that c-ZrO2 surfaces are good models for the industrial used tetragonal ZrO2 supports.

Journal Article↗
PubMed2005

Atomic structure of a thin silica film on a Mo(112) substrate: a two-dimensional network of SiO4 tetrahedra.

The structure of a thin single crystalline SiO(2) film grown on Mo(112) has been studied by scanning tunneling microscopy, infrared reflection absorption spectroscopy, and x-ray photoelectron spectroscopy. In excellent agreement with the experimental results, density functional theory calculations show that the film consists of a two-dimensional network of corner sharing [SiO(4)] tetrahedra, with one oxygen of each tetrahedron binding to the protruding Mo atoms of the Mo(112) surface.

Journal Article↗
PubMed2004

Alpha lipoic acid for dementia.

BACKGROUND: Oxidative processes have been implicated in the pathogenesis of neurodegenerative dementias including Alzheimer's disease. Protecting the central nervous system against these damaging mechanisms may be a useful therapeutic approach. Alpha lipoic acid (ALA) is an endogenous antioxidant that interrupts cellular oxidative processes in both its oxidized and reduced forms. These properties might qualify ALA for a modulatory role in the treatment of people with dementia. OBJECTIVES: To assess the role and clinical efficacy of alpha lipoic acid in the treatment of dementia. SEARCH STRATEGY: A search of the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group (CDCIG) on 3 February 2003 using the terms 'alpha lipoic acid' and 'thioctic'. The CDCIG Specialized register is updated regularly and contains records from all major health care databases (MEDLINE, EMBASE, PsycInfo, CINAHL) as well as from many trials databases. SELECTION CRITERIA: All double-blind randomized placebo-controlled trials examining the efficacy of alpha lipoic acid in dementia DATA COLLECTION AND ANALYSIS: No trials were found that met the selection criteria MAIN RESULTS: No meta-analysis could be performed. A systematic search of the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group, as well as registers of ongoing and unpublished trials could not identify any studies investigating the use of ALA for dementia. REVIEWER'S CONCLUSIONS: In the absence of randomized double-blind placebo-controlled trials investigating ALA for dementia, no evidence exists to explore any potential effects. Until data from trials become available for analysis, ALA cannot be recommended for people with dementia.

Dementia↗
PubMed2004

[Mitigated erysipelas after implantation of foreign material].

When an infection occurs in the incisional area following surgery where foreign materials (i. e. endoprostheses, metal plates or plastic meshes) are implanted, a revision may become necessary because an infection in the area of the implant and involvement of the implant itself cannot be ruled out. In the case of a mitigated erysipelas, cultures taken during the revision seldom show bacterial growth. The disease progresses because surgery does not solve the problem of a weakened immune system and lymph stasis; on the contrary, it usually deteriorates the situation. A high dose antibiotic regimen is recommended as therapy for the mitigated erysipelas instead of an operative revision orally given. levofloxacin has proven to be successful reducing the recurrence rate. The course of two patients with mitigated erysipelas is represented for example in form of case studies. The patients were underwent several surgical revisions. But we had not to explant the endoprostheses at all. Finally both patients were treated with levofloxacin without further relapses.

Aged↗
PubMed2001

Stability and function of interdomain linker variants of glucoamylase 1 from Aspergillus niger.

Several variants of glucoamylase 1 (GA1) from Aspergillus niger were created in which the highly O-glycosylated peptide (aa 468--508) connecting the (alpha/alpha)(6)-barrel catalytic domain and the starch binding domain was substituted at the gene level by equivalent segments of glucoamylases from Hormoconis resinae, Humicola grisea, and Rhizopus oryzae encoding 5, 19, and 36 amino acid residues. Variants were constructed in which the H. resinae linker was elongated by proline-rich sequences as this linker itself apparently was too short to allow formation of the corresponding protein variant. Size and isoelectric point of GA1 variants reflected differences in linker length, posttranslational modification, and net charge. While calculated polypeptide chain molecular masses for wild-type GA1, a nonnatural proline-rich linker variant, H. grisea, and R. oryzae linker variants were 65,784, 63,777, 63,912, and 65,614 Da, respectively, MALDI-TOF-MS gave values of 82,042, 73,800, 73,413, and 90,793 Da, respectively, where the latter value could partly be explained by an N-glycosylation site introduced near the linker C-terminus. The k(cat) and K(m) for hydrolysis of maltooligodextrins and soluble starch, and the rate of hydrolysis of barley starch granules were essentially the same for the variants as for wild-type GA1. beta-Cyclodextrin, acarbose, and two heterobidentate inhibitors were found by isothermal titration calorimetry to bind to the catalytic and starch binding domains of the linker variants, indicating that the function of the active site and the starch binding site was maintained. The stability of GA1 linker variants toward GdnHCl and heat, however, was reduced compared to wild-type.

Amino Acid Sequence↗
PubMed2001

Protection against murine listeriosis by oral vaccination with recombinant Salmonella expressing hybrid Yersinia type III proteins.

In the present study, we have investigated the possibility to engage the Yersinia outer protein E (YopE) as a carrier molecule for heterologous Ag delivery by the type III secretion system of Salmonella typhimurium. Defined secretion and translocation domains of YopE were fused to the immunodominant T cell Ags listeriolysin O and p60 of Listeria monocytogenes. In vitro experiments showed that S. typhimurium allows secretion and translocation of large hybrid YopE proteins in a type III-dependent fashion. Translocation and cytosolic delivery of these chimeric proteins into host cells, but not secretion into endosomal compartments, led to efficient MHC class I-restricted Ag presentation of listerial nonamer peptides. Mice orally vaccinated with a single dose of attenuated S. typhimurium expressing translocated hybrid YopE proteins revealed high numbers of IFN-gamma-producing cells reactive with listeriolysin O 91-99 or p60 217-225, respectively. This CD8 T cell response protected mice against a challenge with L. monocytogenes. In conclusion, these findings suggest that YopE is a versatile carrier molecule for type III-mediated foreign Ag delivery by Salmonella vaccine strains.

Administration, Oral↗
PubMed2001

Nitrogen starvation-induced chlorosis in Synechococcus PCC 7942. Low-level photosynthesis as a mechanism of long-term survival.

Cells of the non-diazotrophic cyanobacterium Synechococcus sp. strain PCC 7942 acclimate to nitrogen deprivation by differentiating into non-pigmented resting cells, which are able to survive prolonged periods of starvation. In this study, the physiological properties of the long-term nitrogen-starved cells are investigated in an attempt to elucidate the mechanisms of maintenance of viability. Preservation of energetic homeostasis is based on a low level of residual photosynthesis; activities of photosystem II and photosystem I were approximately 0.1% of activities of vegetatively growing cells. The low levels of photosystem I activity were measured by a novel colorimetric assay developed from the activity staining of ferredoxin:NADP+ oxidoreductase. Photosystem II reaction centers, as determined by chlorophyll fluorescence measurements, exhibited normal properties, although the efficiency of light harvesting was significantly reduced compared with that of control cells. Long-term chlorotic cells carried out protein synthesis at a very low, but detectable level, as revealed by in vivo [35S]methionine labeling and two-dimensional gel electrophoresis. In conjunction with the very low levels of total cellular protein contents, this implies a continuous protein turnover during chlorosis. Synthesis of components of the photosynthetic apparatus could be detected, whereas factors of the translational machinery were stringently down-regulated. Beyond the massive loss of protein during acclimation to nitrogen deprivation, two proteins that were identified as SomA and SomB accumulated due to an induced expression following nitrogen reduction.

Amino Acid Sequence↗
PubMed2001

Increased first-contact rates for very-late-onset schizophrenia-like psychosis in African- and Caribbean-born elders.

BACKGROUND: Studies have consistently shown a higher incidence of schizophrenia with onset in early adult life in African and Caribbean migrants to the UK. AIMS: To establish the incidence (first-contact rates) of very-late-onset (>60 years) schizophrenia-like psychosis (SLP) in south London and to test the hypothesis that this is higher among African- and Caribbean-born than indigenous elders. METHOD: We identified all new referrals of SLP to the Maudsley Hospital between 1995 and 2000. Demographic details, including age, ethnicity and electoral ward (address), were obtained from case notes. Incidence was estimated using 1997 census data to determine the denominator population for each ethnic group. RESULTS: The incidence of SLP was significantly higher in African- and Caribbean-born than indigenous elders: 172.4 per 100,000 population (95% CI=57.9--286.8) in African- and Caribbean-born males and 323.5 per 100,000 population (95% CI 167.8--479.1) in African- and Caribbean-born females. Rates also were increased in elders from other immigrant groups, but the numbers involved were too small to reach accepted levels of significance. CONCLUSIONS: Large-scale epidemiological studies are needed to determine both the incidence of and the coexistent risk factors for SLP among all elderly migrants, who may constitute a group with high service needs.

Africa↗
PubMed2000

Glucoamylase: structure/function relationships, and protein engineering.

Glucoamylases are inverting exo-acting starch hydrolases releasing beta-glucose from the non-reducing ends of starch and related substrates. The majority of glucoamylases are multidomain enzymes consisting of a catalytic domain connected to a starch-binding domain by an O-glycosylated linker region. Three-dimensional structures have been determined of free and inhibitor complexed glucoamylases from Aspergillus awamori var. X100, Aspergillus niger, and Saccharomycopsis fibuligera. The catalytic domain folds as a twisted (alpha/alpha)(6)-barrel with a central funnel-shaped active site, while the starch-binding domain folds as an antiparallel beta-barrel and has two binding sites for starch or beta-cyclodextrin. Certain glucoamylases are widely applied industrially in the manufacture of glucose and fructose syrups. For more than a decade mutational investigations of glucoamylase have addressed fundamental structure/function relationships in the binding and catalytic mechanisms. In parallel, issues of relevance for application have been pursued using protein engineering to improve the industrial properties. The present review focuses on recent findings on the catalytic site, mechanism of action, substrate recognition, the linker region, the multidomain architecture, the engineering of specificity and stability, and roles of individual substrate binding subsites.

Amino Acid Sequence↗
PubMed2000

Q-switch laser and tattoo pigments: first results of the chemical and photophysical analysis of 41 compounds.

BACKGROUND AND OBJECTIVE: In the Western world, there are at least 20-30 million people with tattoos. Improved self-image and social stigmatization are the main reasons for removing tattoos from skin. Q-switched lasers are applied to destroy the tattoo compounds in the skin. The treatment of tattoos containing ink often gives excellent results, whereas the results of treatments for coloured tattoos are not predictable and usually are worse. The chemical structure and the absorption spectra of the tattoo pigments are usually unknown. However, the efficacy of the treatment by using light of different Q-switched lasers (wavelengths 510, 532, 694, 755, 1064 nm) is correlated to both the chemical structure of the tattooed compounds yielding specific absorption spectra and the laser wavelength used. STUDY DESIGN/MATERIALS AND METHODS: A structural and spectroscopic analysis of 41 coloured pigments was performed. RESULTS: The 41 substances were identified, and they consist of 16 individual chemicals of different structured well-known industrial organic pigments. The absorption spectra of the 16 pigments were measured quantitatively. CONCLUSION: The results of the present analysis explain to some extent the outcome of clinical studies regarding laser therapy of coloured tattoos. Because the laser energy used produces a high temperature in the azo or polycyclic pigments, it is necessary to investigate whether that change causes possibly toxic or cancerogenic compounds.

Coloring Agents↗
PubMed2000

[Adenocarcinoma in a tail-gut cyst: a rare cause of recurrent perianal fistula].

A 58-year-old woman was initially externally diagnosed in 1983 with a presacral mass, which was subsequently treated as an abscess. Thereafter, the patient experienced recurrent perianal fistulas. Further diagnostic studies revealed a cystic tumor, considered to be an epidermoid cyst, which was located in the inferior pelvis and was consequently removed. Histologically, cystic scar tissue was found with a highly differentiated adenocarcinoma which measured 4 cm. Later on, the patient again experienced perianal fistulas originating from a renewed presacral mass. As a result, an abdominal-perianal rectum extirpation and a partial resection of the sacrum with placement of a descendostomy were done. Histologically, adenocarcinoma tissue was found at the base of a tail-gut cyst. One year following her operation, the patient is free from any complaints and relapses. The tail-gut cyst is a very rare entity which arises from the inadequate involution of the tail-gut during embryonal development. A malignant transformation occurs in 10% of the cases. In the case of recurrent perianal fistulas and cystic masses between the rectum and os sacrum or os coccygeum, a tail-gut cyst should be taken into consideration, the goal being its complete removal.

Adenocarcinoma↗
PubMed2000

Prospective memory: a secondary task with promise.

This paper examines the utility of prospective memory as a secondary task. For this purpose, the results of seven experiments were analysed to evaluate the sensitivity of prospective memory, making a direct comparison with another secondary task (reaction time). Both tasks were used as subsidiary elements in a complex task environment, the design of which was based on the micro-world research paradigm. The results indicated that prospective memory was slightly more vulnerable to variations in experimental conditions than was reaction time. The paper concludes that, overall, prospective memory appears to be a suitable secondary task. This is partly attributed to the element of self-initiation, which is a feature of some prospective memory tasks. It is recommended to use time-based and pulse-based prospective memory tasks since they seem to be the more sensitive.

Humans↗
PubMed2000

The use of micro-worlds for human factors research in extended spaceflight.

This article provides an analysis of the utility of micro-worlds for human factors research in extended spaceflight. It outlines potential areas of application of the micro-world research paradigm in the context of spaceflight. While the research literature provides several examples of micro-worlds that simulate different work environments of high complexity, little work has been done with this tool in the operational environment of spaceflight. The author presents a micro-world, called CAMS, that has been especially developed for use in space-related research. The results from a research programme (comprising seven studies using CAMS) are presented. Based on a comparative analysis of the benefits and limitations of micro-worlds compared to other simulation types, the author argues that micro-worlds can be a very effective tool, provided their inherent limitations are taken into consideration.

Astronauts↗
PubMed2000

A conceptual framework for designing micro-worlds for complex work domains: a case study of the Cabin Air Management System.

A conceptual framework for the design of micro-worlds is presented in this paper. This is illustrated by a micro-world, called Cabin Air Management System (CAMS), that has been used in a research program to investigate human behavior during work with complex systems. Although CAMS is based on the operational context of spaceflight, its underlying principles correspond to a process control task. The authors propose a theoretical framework for micro-world design, which was used to guide the development of the CAMS micro-world. This may provide a helpful guideline for researchers wishing to develop a micro-world by using a more structured approach. A detailed technical description of CAMS is given to demonstrate the kind of real-world scenarios that may be simulated with this task environment. Finally, general aspects of the utility of micro-world research are discussed.

Air Conditioning↗
PubMed2000

Effects of training on short- and long-term skill retention in a complex multiple-task environment.

The paper reports the results of an experiment on the performance and retention of a complex task. This was a computer-based simulation of the essential elements of a spacecraft's life support system. It allowed the authors to take a range of measures, including primary and secondary task performance, system intervention and information sampling strategies, mental model structure, and subjective operator state. The study compared the effectiveness of two methods of training, based on low level (procedure-based) and high level (system-based) understanding. Twenty-five participants were trained extensively on the task, then given a 1-h testing session. A second testing session was carried out 8 months after the first (with no intervening practice) with 17 of the original participants. While training had little effect on control performance, there were considerable effects on system management strategies, as well as in structure of operator's mental model. In the second testing session, the anticipated general performance decrement did not occur, though for complex faults there was an increase in selectivity towards the primary control task. The relevance of the findings for training and skill retention in real work environments is discussed in the context of a model of compensatory control.

Adult↗