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Biomedical subjects

J Sauer

Publications and source records attributed to J Sauer.

At least 37 records · Page 2Linked to original sources
PubMed2000

The Synechococcus strain PCC 7942 glnN product (glutamine synthetase III) helps recovery from prolonged nitrogen chlorosis.

We report the cloning and sequencing of the glnN gene encoding a class III glutamine synthetase from the cyanobacterium Synechococcus strain PCC 7942. Mapping of the transcriptional start site revealed a DNA sequence in the promoter region that resembles an imperfect NtcA binding motif. Expression of glnN is impaired in NtcA- and P(II)-deficient mutants. The only parameter which was negatively affected in the glnN mutant compared to the wild type was the recovery rate of prolonged nitrogen-starved cells with low concentrations of combined nitrogen.

Bacterial Proteins↗
PubMed2000

PACT to the future.

Explore the source record for details and available documents.

Community Health Services↗
PubMed2000

[Conservative and surgical antireflux therapy as prevention of carcinoma].

INTRODUCTION: Based on findings in literature, the effectiveness of the medical versus operative antireflux therapy was examined as a prophylaxis to impede the formation of an adenocarcinoma in the case of Barrett esophagus. MEDICAL ANTIREFLUX THERAPY: Despite reports of success following the administration of Omeprazole, the inhibition of acid secretion does not lead to the regression of the endobrachyesophagus for most patients. The partial shortening of the Barrett segment is reported in up to 78% of cases, however the precancerous changes of the distal esophagus are not eliminated. In spite of medical therapy with proton pump inhibitors, up to 6% of dysplasias become metaplasias per year. In 3% of the patients, an adenocarcinoma arises. OPERATIVE ANTIREFLUX THERAPY: It is reported in the literature that there is a partial regression of the endobrachyesophagus in up to 34% of cases and complete regression in up to 11% of cases following operative antireflux therapy. Despite a macroscopically unchanged Barrett segment following a fundoplication or semifundoplication procedure, a complete regression of minor dysplasias and the complete regression of intestinal metaplasias is possible. In only 30% of patients, postoperative atypical findings were ascertainable. Nevertheless, a severe change can appear in the cylinder epithelium of the remaining Barrett segment following an operative antireflux therapy, up to the formation of an adenocarcinoma (1-9%). For this reason, the patients must be endoscopically and histologically examined at regular intervals following the antireflux operation. CONCLUSION: In the case of evidence of severe dysplasias in the Barrett segment, the attempt at carcinoma prophylaxis by means of antireflux therapy is no longer indicated. With the appearance of mild dysplasias and complete intestinal metaplasias in the Barrett esophagus, an antireflux operation can lead to a reduction in the grade of atypical cells. In cases of existing metaplasia or the presence of mild dysplasias, the administration of proton pump inhibitors or H2 blockers is only indicated as a symptomatic therapy.

Adenocarcinoma↗
PubMed1999

[Littoral-cell angioma--a rare differential diagnosis on splenic tumors].

UNLABELLED: HISTORY AND PRE-ADMISSION FINDINGS: Routine abdominal sonography of a 51-year-old man 6 years after removal of the right testis and radiotherapy for a seminoma revealed a 3 cm mass within the spleen. INVESTIGATIONS: All biochemical tests were normal. Computed tomography (CT) and magnetic resonance imaging confirmed the tumour which had not been present on the CT before the seminoma had been treated. No other space-occupying lesions were found in the thorax and abdomen. TREATMENT AND COURSE: A splenectomy was performed because a metachronous metastasis of the seminoma was suspected. The operation and subsequent course were uneventful. At operation the tumour had been diagnosed as an haemangioma because of its gross appearance, but histological and immunohistochemical examination revealed a littoral cell angioma. CONCLUSION: The littoral cell angioma is a benign vascular lesion in the red pulp of the spleen, which may be caused by different stimuli such as chronic infection or tumours. This case illustrates, that this tumour should be considered in the differential diagnosis of an unclear neoplasm in the spleen.

Diagnosis, Differential↗
PubMed1999

Nitrogen starvation in synechococcus PCC 7942: involvement of glutamine synthetase and NtcA in phycobiliprotein degradation and survival

The nondiazotrophic cyanobacterium Synechococcus sp. strain PCC 7942 responds to nitrogen deprivation by differentiating into nonpigmented resting cells able to survive prolonged periods of starvation. The degradation of photosynthetic pigments, termed chlorosis, proceeds in an ordered manner in which the light-harvesting phycobiliproteins are degraded prior to chlorophyll. Here, we show that the function of the global transcription activator of nitrogen-regulated genes, NtcA, is required for the sequential pigment degradation and cell survival. The P(II) protein, known to signal the nitrogen status of the cells, is most probably not involved in the perception of the nitrogen-starvation-specific signal since in a mutant lacking P(II), chlorosis proceeded in the same manner as in the wild type. Inhibition of glutamine synthetase with l-methionine sulfoximine led to a rapid decrease of apc mRNA and to an increase of nblA mRNA levels, which is characteristic for nitrogen deprivation, suggesting that nitrogen starvation is sensed by a metabolic signal connected to glutamine synthetase activity. However, l-methionine sulfoximine treatment did not induce phycobiliprotein degradation, but led to an immediate cessation of this proteolytic process after its induction by nitrogen deprivation. This suggests that the proteolytic activity elicited by the expression of nblA has to be supported by glutamine synthetase activity.

Journal Article↗
PubMed1999

Multiple-task performance on a computer-simulated life support system during a space mission simulation.

This paper presents an experiment which examined the effects of isolation and confinement during a simulation of a short-term space mission. During the 7-day spaceflight simulation, four Canadian astronauts were tested daily on a 30-min performance task. The task, CAMS (Cabin Air Management System), represents a computer-based simulation of a generic life support system. As a multiple-task environment, it allows the measurement of a wide range of task management variables such as primary and secondary task performance, and system control activities. Measures of subjective state variables were also taken. The results did not show any evidence of serious performance decrements for any crew member. The analysis revealed different adjustment patterns with which crew members responded as a function of mission duration and variations in workload. Among the secondary tasks employed, prospective memory was found to be more sensitive than reaction time to increases in workload. The paper concludes with a discussion of the utility of spaceflight simulations and computer-based simulations of space work.

Adaptation, Psychological↗
PubMed1999

Expression of the Methanobacterium thermoautotrophicum hpt gene, encoding hypoxanthine (Guanine) phosphoribosyltransferase, in Escherichia coli.

The hpt gene from the archaeon Methanobacterium thermoautotrophicum, encoding hypoxanthine (guanine) phosphoribosyltransferase, was cloned by functional complementation into Escherichia coli. The hpt-encoded amino acid sequence is most similar to adenine phosphoribosyltransferases, but the encoded enzyme has activity only with hypoxanthine and guanine. The synthesis of the recombinant enzyme is apparently limited by the presence of the rare arginine codons AGA and AGG and the rare isoleucine AUA codon on the hpt gene. The recombinant enzyme was purified to apparent homogeneity.

Amino Acid Sequence↗
PubMed1999

Performance evaluation in analogue space environments: adaptation during an 8-month Antarctic wintering-over expedition.

BACKGROUND: This paper reports a study which examined the impact of long-term isolation and confinement on multiple-task performance. METHODS: A group of 10 scientists and 6 technicians from a French wintering-over expedition in the Antarctic participated in the 8-mo study. The group was tested 8 times on a computerized simulation of a complex life support system. The task environment allowed the measurement of primary and secondary task performance, system control activities and subjective operator state. RESULTS: No signs of serious performance decrements were observed but a number of subtle indications of hidden decrements emerged. The data also revealed strong differences in performance between the professional groups. Finally, the paper discusses the implications of the work for extended spaceflight.

Adult↗
PubMed1999

Maintenance of complex performance during a 135-day spaceflight simulation.

BACKGROUND: The maintenance of crew performance during extended space missions has been a major concern because of the problems associated with prolonged isolation and confinement. Previous research has failed to address this problem by not using appropriate performance tests. METHOD: Three Russian cosmonauts were tested on a PC-based simulation of a spacecraft's life support system during a 135-d simulation of a MIR spaceflight. A complex multiple-task environment was used to examine a comprehensive range of task management variables, including both primary and secondary task performance, control activity and information sampling behavior. Subjective state variables were also measured. RESULTS: The data suggested an overall successful adjustment to isolation and confinement, though some indications of temporary disruptions of some performance indicators were observed. Information sources were sampled less frequently with increasing mission length while system control activities showed a tendency to increase. CONCLUSION: Suggestions are made to address the problem of continuous learning during repeated testing sessions. Using well-designed computer simulations of complex task environments appears to be a promising approach for the evaluation of crew member performance.

Adult↗
PubMed1998

Cytokine expression and molecular mechanisms of their auto/paracrine regulation of anterior pituitary function and growth.

The pituitary gland expresses cytokines and their receptors. IL-2 receptor transcripts and protein products are co-localized in ACTH-, PRL-, and GH-producing cells (double immunofluorescence). IL-2 and IL-6 (1-1000 IU/ml) are involved in the autocrine/paracrine regulation of normal and tumor (GH3 mammosomatotroph cell line and adenoma cell cultures) anterior pituitary hormone-producing cell growth (cell number, DNA synthesis, c-fos mRNA expression and autoradiography combined with hormone staining). IL-1 regulates the growth of normal pituitary cells but does not act on GH3 cells. IL-1ra, which blocks this action, is expressed in tumoral pituitary (mainly GH- and ACTH-) cells. In ACTH- cells, IL-1 enhances glucocorticoid feedback, stimulating glucocorticoid response element transcriptional activity. Cytokines, through specific functional receptors, act as inter/auto-cellular factors that regulate not only the function but also the growth of anterior pituitary cells.

Animals↗
PubMed1998

The Th1 and Th2 cytokines IFN-gamma and IL-4 antagonize the inhibition of monocyte IL-1 receptor antagonist by glucocorticoids: involvement of IL-1.

Monocytes express IL-1 and IL-1 receptor antagonist (IL-1Ra) in response to lipopolysaccharide (LPS). IL-1 self-induction contributes to the increase in IL-1 following LPS stimulation. LPS-stimulated IL-1 and IL-1Ra production are inhibited by glucocorticoids. In the present work we examined the regulation of IL-1Ra by Th1 cytokine IFN-gamma, Th2 cytokine IL-4, glucocorticoids and IL-1 in human monocytes. We demonstrate that IL-1 contributes to LPS-induced IL-1 Ra expression as shown by IL-1 blockade in LPS-stimulated monocytes using a specific anti-IL-1beta antibody or recombinant IL-1Ra. Glucocorticoids inhibited IL-1beta-stimulated IL-1Ra mRNA expression and protein production. Glucocorticoids inhibited both IL-1-mediated and non-mediated LPS stimulation of IL-1Ra expression. Both IFN-gamma and IL-4 reversed the inhibitory effect of glucocorticoids on IL-1Ra expression and secretion. The effect of IFN-gamma was blocked by pretreatment of monocytes with an anti-IL-1beta blocking antibody, whereas the effect of IL-4 could not be blocked, demonstrating that IFN-gamma acts through a mechanism dependent on endogenous IL-1 production, whereas IL-4 acts through an IL-1-independent one. Consistent with this finding, IFN-gamma (but not IL-4) failed to reverse the inhibitory effect of glucocorticoids when stimulated by IL-1, and only IL-4 combined with IL-1 showed synergism resulting in an increase in IL-1 Ra production. The differential regulation and involvement of IL-1 in the expression of IL-1Ra by IFN-gamma, IL-4 and glucocorticoids sets the level of monocyte responsiveness during the Th1 or Th2 responses.

Glucocorticoids↗
PubMed1998

Task analysis for the investigation of human error in safety-critical software design: a convergent methods approach.

An investigation was conducted into sources of error within a safety-critical software design task. A number of convergent methods of task- and error-analysis were systematically applied: hierarchical task analysis (HTA), error log audit, error observation, work sample and laboratory experiment. HTA, which provided the framework for the deployment of subsequent methods, revealed possible weaknesses in the areas of task automation and job organization. Application of other methods within this more circumscribed context focused on the impact of task and job design issues. The use of a convergent methods approach draws attention to the benefits and shortcomings of individual analysis methods, and illustrates the advantages of combining techniques to analyse complex problems. The features that these techniques should possess are highlighted.

Ergonomics↗
PubMed1998

Interleukin-1 beta enhances interleukin-1 receptor antagonist content in human somatotroph adenoma cell cultures.

In addition to the well-known modulation of immune and inflammatory responses, the interleukin-1 (IL-1) system has been shown to be involved in the regulation of anterior pituitary hormone secretion and growth. We previously demonstrated that IL-1 receptor antagonist (IL-1ra) is expressed in human pituitary adenomas cultured in vitro. In the present study, we investigated the regulation of IL-1ra protein by IL-1 beta (1-100 U/mL) in human somatotroph adenomas (n = 9) cultured for 12-48 h. IL-1 beta significantly enhanced the concentration of IL-1ra dose dependently in the somatotroph adenoma cell lysates, whereas IL-1ra concentrations remained unchanged in the culture supernatants. Furthermore, basal IL-1ra concentrations were significantly higher in the cell lysates compared with the corresponding culture supernatants. The regulation of IL-1ra in somatotroph adenoma cells is different from human cultured monocytes, in which IL-1 beta significantly stimulated IL-1ra secretion into the culture supernatants, and no change of intracellular IL-1ra content was observed. Incubation of the somatotroph adenoma cells with 100 U/mL IL-1 beta did not result in a change of GH concentrations in the culture supernatants. Enhancement of intracellular IL-1ra protein by IL-1 beta may represent a mechanism intrinsic to somatotroph adenoma cells to counterregulate the response to IL-1 beta on hormone secretion or cellular growth.

Adenoma↗
PubMed1998

Effects of sleep deprivation and user interface on complex performance: a multilevel analysis of compensatory control.

This study was carried out to test the compensatory control model, which predicts performance maintenance under stress at the expense of effort and increased selectivity. It examined the effects of sleep deprivation on performance in an automated process control task based on a simplified life support system with two types of operator control panel interface: machine centered (M-C), in which access to the system was scheduled by the computer, and human-centered (H-C), in which access was ad-lib. The task environment also permitted the analysis of changes in strategy and in subsidiary activities (alarm reaction time, prospective memory). In a 2 x 2 repeated-measures design, 16 participants carried out the task with each interface after both normal sleep and one night of sleep deprivation (SD). No effects of SD were observed on primary task performance. As predicted, SD effects were confined to strategy changes and subsidiary task impairment and occurred only under the (low control) M-C interface. Subjective effort was increased under SD, with greater increases of effort associated with high levels of performance protection. The findings provide strong evidence in favor of the compensatory control model and argue for the use of complex, multilevel tasks in the analysis of performance under stress. Actual or potential applications include the development of more sensitive performance-testing systems based on multilevel analysis of decrement, and the design of interfaces for shift work and other suboptimal work conditions.

Adult↗
PubMed1998

[A methodological study in a space flight simulation context].

To study the effects of isolation and confinement on small groups during long space flights, it is habitual to use closed hyperbaric ground chambers. For the first time, the European Space Agency made use of a nautral environment taking advantage of an Antarctic winter-over at the French Dumont d'Urville Station. The main objective of that study ("International Antarctic Psychological Programme"), was to compare different Russian tests used for training cosmonauts to a W. European approach validated during previous winter studies and European ground chamber simulations. Russian techniques appeared to be oriented to a narrow range of phenomena and unsuited to discern the adjustment to stress conditions.

Adaptation, Psychological↗
PubMed1998

[Is graduate education for surgical specialist adequate? Results of a survey of surgical assistants in Berlin-Brandenburg].

A questionnaire was sent to all surgical registrars in Berlin and Brandenburg. The number of operations and other characteristic facts in surgical training were requested; 127 answers were sent back. The number of operations on colon, small intestine, stomach, and breast was not adequate to the required number of operations for specialist qualification in Berlin and Brandenburg. Although not representative, the inquiry shows a trend in surgical training.

Berlin↗
PubMed1997

Ab initio predictions of zeolite structures and 29Si NMR chemical shifts.

A recent shell-model potential parameterized on ab initio data is used for predicting the all-silica structures of zeolites MFI, MEI, MTW, TON, FAU and of alpha-quartz. Cluster models are defined around each site and the 29Si NMR shielding constants are calculated by ab initio techniques (GIAO-HF). Good agreement with observed 29Si NMR chemical shifts is found. Comparison is made with shifts calculated for observed structures. The structures predicted by the ab initio shell-model potential prove as accurate as the observed ones when judged on the quality of the calculated 29Si NMR spectra.

Isotopes↗