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Biomedical subjects

J Springer

Publications and source records attributed to J Springer.

At least 37 records · Page 2Linked to original sources
PubMed1999

Influence of Oxygen Plasma Treatment of PAN-Based Carbon Fibers on Their Electrokinetic and Wetting Properties.

Oxygen plasma treatment was used to modify the surfaces of high-tenacity polyacrylonitrile-based carbon fibers. Changes in the surface composition of plasma-treated fibers were investigated by electrokinetic (zeta-potential) measurements as well as by wetting studies to evaluate the solid surface tension. Treating carbon fibers in an oxygen plasma results in an increased surface acidity, as can be seen from the overall shape of the zeta = f(pH) function and from the shift of the isoelectric points toward lower pH. The increased surface polarity improves the wetting behavior versus water. Although the fibers become more hydrophilic, the adsorption of ions from the electrolyte solution, which should compete with water adsorption, increases. Almost no changes in the surface morphology could be monitored by scanning electron microscopy. However, wetting and zeta-potential measurements confirm changes at the fiber surface. zeta-Potential measurements and wetting (contact angle) measurements complement each other. This allows observation of changes taking place in the surface chemistry after modifications applied to industrially available unmodified carbon fibers. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Identification and characterization of MmORC4 and MmORC5, two subunits of the mouse origin of replication recognition complex.

Two new members of the mouse origin recognition complex (ORC) have been cloned that are closely related to Saccharomyces cerevisiae ORC4 and ORC5 as well as to their human homolog. Both MmORC4p and MmORC5p have a putative nucleotide triphosphate binding motif. Transcription of MmORC4 and MmORC5 is not suppressed in mouse NIH3T3 fibroblasts made quiescent by serum starvation. The transcription levels of both ORC genes are constantly high in all phases of the cell cycle. A screen based on the two-hybrid approach suggests that the product of the ORC4 gene interacts with the ORC2, but not with the ORC1 protein. The conservation of structure among members of the ORC4- and ORC5-related family of proteins suggests that these proteins play a key role in the initiation of DNA replication in all eukaryotes.

3T3 Cells↗
PubMed1999

Asymptomatic primary biliary cirrhosis: a study of its natural history and prognosis.

OBJECTIVE: To document the natural history of asymptomatic primary biliary cirrhosis and identify prognostic features that would predict the development of symptomatic disease. METHODS: A retrospective chart review of all patients with abnormal liver biochemical tests and antimitochondrial antibody-positive, liver biopsy-compatible primary biliary cirrhosis who were seen in a single tertiary care center between 1983 and 1994 was performed. Statistical analysis using Cox regression was employed to compare survival of the study population with an age- and gender-matched control population and to identify potential prognostic variables. RESULTS: Ninety-one patients were included. Median age at presentation was 53.2 yr. Ninety percent were female. Median follow up was 61.2 months (range 7-206 months). Thirty-six percent (33 patients) became symptomatic with 11% (10 patients) progressing to death or liver transplant. Median predicted length of survival from onset of disease for the entire cohort was 14 yr. Patient survival was less than that predicted for an age- and gender-matched control population (p < 0.05). Univariate and multivariate analysis on a broad spectrum of clinical, biochemical, and histological features at the time of initial presentation failed to reveal any prognostic variables that would distinguish those who would become symptomatic from those who would remain symptom-free. Specifically, three primary variables of interest (associated autoimmune disorders, hepatomegaly, and histological stage) were not found to predict prognosis. CONCLUSION: Patients who present with asymptomatic primary biliary cirrhosis have a shorter life span than the general population. Presently, there are no prognostic features that identify the patients who will develop progressive disease from those who will remain symptom-free. Therefore, treatment should be offered to all patients.

Adult↗
PubMed1999

Verbal memory impairment after left insular cortex infarction.

PET studies have shown an association between changes in blood flow in the insular cortex and verbal memory. This study compared verbal memory profiles between a group of four right handed patients with right insular infarction and a group of six right handed patients with left insular infarction. Patient groups were comparable in age, education, and sex. Patients were administered memory tests about 4-8 weeks poststroke. Patients with left insular lesions showed significantly poorer immediate and delayed verbal memory as measured by story A of the WMS-R logical memory I (t=-2.73, p<0.03) and logical memory II (t=-4.1, p<0.004) subtests as well as the CERAD word list memory (delayed recall) (t=-2.4, p<0.05). These findings indicate that left insular damage is associated with poorer performance on verbal memory tasks. The findings suggest that the insula may be part of a functional network that mediates verbal memory.

Aged↗
PubMed1999

Identification and chromosomal localization of murine ORC3, a new member of the mouse origin recognition complex.

A new member of the murine origin recognition complex (ORC) related to Saccharomyces cerevisiae ORC3 has been cloned. Transcription of ORC3 is not suppressed in mouse NIH3T3 fibroblasts made quiescent by serum starvation. The transcription level of the ORC3 gene is constantly high in all phases of the cell cycle. Murine ORC3 protein contains a putative nuclear localization signal and a non-basic helix-loop-helix motif. Both motifs are conserved in eukaryotes. A potential dimerization partner of ORC3p in the murine ORC complex is ORC1p which also contains an HLH motif. This HLH motif is also highly conserved in all eukaryotic ORC1 proteins. Comparison of murine ORC3p with other ORC3-related proteins shows high amino acid homology and motif conservation leading to the conclusion that ORC3p is part of the initiation machinery conserved in eukaryotes. The mouse ORC3 gene Orc3 was assigned to mouse chromosome 4A3 by fluorescence in situ hybridization (FISH) analysis.

3T3 Cells↗
PubMed1998

Structure of the enzymatically synthesized fructan inulin.

Construction, purification and characterization of a fusion protein of maltose-binding protein of Escherichia coli and the fructosyltransferase of Streptococcus mutans is described. With the purified protein, in vitro synthesis of inulin was performed. The obtained polysaccharide was characterized by high-performance size-exclusion chromatography (HPSEC) and static light scattering (SLS) in dilute aqueous and dimethyl sulfoxide solution. For all samples very high molecular weights between 60 x 10(6) and 90 x 10(6) g/mol and a remarkable small polydispersity index of 1.1 have been determined. Small root-mean-square radii of gyration point to a compact conformation in dilute solution. No difference between native and enzymatically synthesized inulin was observed by X-ray powder diffraction and thermoanalysis of solid samples.

ATP-Binding Cassette Transporters↗
PubMed1998

A Generalized Drop Length-Height Method for Determination of Contact Angle in Drop-on-Fiber Systems

A generalized drop length-height method is introduced here for the determination of contact angle in the drop-on-fiber systems. This method overcomes some of the difficulties encountered in the practice by applying the common maximum drop length-height method to determine the contact angle. Furthermore, with this new generalized method a large part of a drop profile can be used in the calculation, which reduces the statistical error of the determination and improves the reliability and accuracy of the obtained results. The method has been examined using both the theoretically simulated and the experimentally obtained drop profiles. The accuracy of the method has been estimated to be in order of 0.5-1degrees for the drop profiles of usual experimental quality, which can be obtained using common digital image processing hardware and software. Copyright 1998 Academic Press. Copyright 1998Academic Press

Journal Article↗
PubMed1998

Stress and strain of short haul bus drivers: psychophysiology as a design oriented method for analysis.

Psychophysiological measures offer objective information for workplace design according to user requirements. They are, however, rarely applied in industrial practice due to weak points from the designer's point of view, such as the differentiation of various superimposed stressors, inter-individual differences, and the effort required for data acquisition and handling. In this study a set of psychophysiological methods was used to analyse bus driver workplaces as a basis for redesign, and afterwards to evaluate design improvements. During inner-city operation bus drivers are exposed to a particular workload situation, especially due to the high density of traffic and bus stops. Their job is characterized by highly frequent and often simultaneous task execution, performed with a compulsory body posture and under exposure to vibration and noise. To reduce the workload related to the equipment and tasks of bus driving, a research project was initiated to design a new driver workplace that meets the specific ergonomic requirements of the drivers. A detailed workload analysis, consisting of a task analysis, a strain analysis derived from ECG measures and an eye movement analysis was performed during public bus driving in different cities and with different drivers and bus types. Although the results have to be considered as somewhat limited owing to the methodological restraints and conditions of a field study, they provided valuable guidance for design. A new concept for the driver cabin was created based on this database. After installation, this design was evaluated by similar psychophysiological measures. Comparison of the pre- and post results indicates that the redesigned work station reduced workload levels.

Adult↗
PubMed1997

Light Scattering Experiments on Shear Induced Structures of Micellar Solutions

The formation of shear induced structures (SIS) of a mixed micellar solution of tetradecyldimethylaminoxide and sodium dodecylsulfate is studied by light scattering experiments under shear (rheo-optical method). In the shear rate- as well as in the time-dependent measurements we found an aggregation process taking part in the SIS formation. Below the critical shear rate for the occurrence of SIS, the shear rate dependent experiments show an increased scattering intensity, indicating micellar associates. Above the critical shear rate, we found structures oriented in the direction of flow. The time dependent measurements show that the SIS formation can be regarded as a process which can be divided into three stages: induction-aggregation-orientation. After the aggregation, we found a temporal process in which the orientation increases to reach complete orientation in the direction of flow.

Journal Article↗
PubMed1997

Cloning and expression of the delta 9 fatty acid desaturase gene from Cryptococcus curvatus ATCC 20509 containing histidine boxes and a cytochrome b5 domain.

To allow genetic modification of the fatty acid biosynthesis routes in the lipid-accumulating yeast Cryptococcus curvatus the delta 9 fatty acid desaturase gene was cloned and characterized. The 1668-bp gene encodes a protein of 556 amino acids with a calculated molecular mass of 62 kDa. The gene shows strong homology to previously cloned delta 9 fatty acid desaturase genes from yeast and rat. Homology includes three histidine boxes characteristic for membrane-bound desaturases and a cytochrome b5 domain responsible for electron transport. The delta 9 desaturase gene has a high G+C content of 61% and displays a codon usage different from that of Saccharomyces cerevisiae, but similar to that of the basidiomycete Schizophyllum commune. Expression of the delta 9 desaturase gene of C. curvatus ATCC 20509 was studied in the presence of different fatty acids in the growth medium. Repression of desaturase mRNA signals was found if fatty acids with a double bond at the delta 9 position were present. Fatty acids with a double bond at another position (delta 10 or delta 6) or saturated fatty acids had no effect on the transcription of the cloned gene.

Amino Acid Sequence↗
PubMed1997

Statistical planning and analysis considerations in the evaluation of in vitro alternatives to whole animal use for eye irritation testing.

Reports from the IRAG Working Groups assessing the current status of in vitro alternatives to whole animal eye irritation tests reflect some common approaches. Although each Working Group studied a particular class of assay, typically all Groups evaluated the in vitro alternatives on the basis of correlation with an in vivo test and the statistical significance of that correlation. However, the data furnished to them by the testing organizations had been obtained with little or no standardization of procedures for testing and evaluation of results. This paper presents issues of design and execution of such test programs that are of statistical concern, including objectives of the evaluation process; limitations of correlation; sources of variation and distinction between actual replication and repeated measurements; evaluation of the predictive ability of in vitro tests; association criteria; and other approaches to such evaluation programs. The distinction between statistical significance and toxicological significance is pointed out. Suggestions are presented for standardization of test protocols, test materials and evaluation programs for both in vitro and in vivo tests. A central repository for such standardization, under the aegis of a government agency, professional standards organization, university or research institute, would be a valuable asset. An addendum is furnished to illustrate assertions about a number of factors influencing correlations and their statistical significance.

Animal Testing Alternatives↗
PubMed1996

Determination of Interfacial Tension from the Profile of a Pendant Drop Using Computer-Aided Image Processing

A method of profile optimization for determining the surface and interfacial tension (IFT) of liquid-fluid systems from the profile of a pendant drop is described. A new, versatile routine for estimating the drop shape parameter is introduced. The factors that affect the available accuracy of the method have been analyzed using theoretical simulations. It was found that the tilt of the drop profiles may lead to large errors in the resultant IFT values if the tilt was not corrected before or during the optimization procedure. This effect could be reduced drastically if a profile were averaged between its two sides and the mean profile were used for optimization. The aspect ratio of a drop image (or profile) can be determined reliably by considering it one of the parameters to be optimized. The dependence of the error in the resultant IFT value on the error in the aspect ratio was found to be highly sensitive to drop shape. The available accuracy of IFT determination using this method depends strongly on the precision of the determination of the drop profiles. After error analysis using theoretical simulations a 95% confidence interval of ca. 0.05 and 0.12% was estimated for this method for the profiles determined with maximum statistical error of 3.5 and 7.0 μm, respectively.

Journal Article↗
PubMed1996

Determination of Interfacial Tension from the Profile of a Pendant Drop Using Computer-Aided Image Processing

The reliability of the method described in the preceding paper (B. Song and J. Springer, J. Colloid Interface Sci. 183, in press, 1996) for the determination of surface and interfacial tension (IFT) of liquid-fluid systems from the profile of a pendant drop has been studied experimentally. Influences on the resultant IFT values from factors such as the location of the drop profile and illumination conditions are considered. The reproducibility and accuracy of the measurement method were examined by measuring the time dependence of polyethylene glycol (PEG600)/air and water/air systems and by determining the temperature dependence of the polyethylene glycol (PEG6000)/N2 and LD (low-density) polyethylene/N2 systems. The effect of drop vibrations on the accuracy of the method is discussed.

Journal Article↗
PubMed1996

Cloning, sequence and expression in Escherichia coli of the gene encoding phosphofructokinase from Bacillus macquariensis.

A chromosomal DNA fragment containing the Bacillus macquariensis (Bm) ATP-dependent phosphofructokinase-encoding gene (pfk) was cloned from a subgenomic library in pUC19 using a PCR-derived probe. The region containing pfk, including flanking sequences, was sequenced and the deduced amino acid sequence (aa) was found to be homologous to other PFK, but it contained two single-aa changes conserved in a range of other organisms from pro- and eukaryotic origins. Enzymatic studies with PFK purified from overproducing Escherichia coli (Ec) host cells showed that the Bm enzyme is similar to B. stearothermophilus (Bs) PFK in many respects and that it is relatively cold stable.

Amino Acid Sequence↗