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At least 163 records · Page 9Linked to original sources
PubMed1998

Pulse application of platelet-derived growth factor enhances formation of a mineralizing matrix while continuous application is inhibitory.

Platelet-derived growth factor (PDGF) stimulates chemotaxis and proliferation of osteoblasts, and induces bone formation in vivo. To determine how PDGF might regulate these cells, the effect of PDGF on long-term mineralizing cultures of fetal rat osteoblastic cells was examined. Although PDGF increased cell proliferation in these cultures, continuous treatment with PDGF caused a dose-dependent decrease in mineralized nodule formation. When cells were treated with multiple, brief (1 day) exposures to PDGF at the osteoblast differentiation stage, there was a significant 50% increase in mineralized nodule area. Based on modulation of alkaline phosphatase activity it appears that longer-term exposure to PDGF reduces mineralized nodule formation largely by inhibiting differentiated osteoblast function, while short-term exposure enhances proliferation without inhibiting the differentiated phenotype. Thus, the ultimate affect of PDGF on bone formation is likely to reflect two processes: a positive effect through enhancing cell number or a negative effect by inhibiting differentiated function. The inhibitory effect of PDGF on formation of a mineralized matrix is unlikely to be simply a result of enhanced proliferation of "fibroblastic" cells since cultures treated with PDGF for 3 days and then transferred to new plastic dishes exhibited a 70% increase in mineralized nodule area compared to controls. These results would predict that multiple, brief exposures to PDGF would enhance bone formation in vivo, while prolonged exposure to PDGF, which is likely to occur in chronic inflammation, would inhibit differentiated osteoblast function and limit bone regeneration.

Animals↗
PubMed2001

An industrial application of multiparameter flow cytometry: assessment of cell physiological state and its application to the study of microbial fermentations.

BACKGROUND: When using traditional microbiological techniques to monitor cell proliferation and viability, stressed, sublethally injured, or otherwise "viable but nonculturable" cells often go undetected. Because of this, such cells often are not considered by mathematical models used to predict bioprocess performance on scale-up and inaccuracies result. Therefore, analytical techniques, decoupled from postsampling growth, are desirable to rapidly monitor individual cell physiologic states during microbial fermentations. METHODS: Microbial cells, including Escherichia coli, Rhodococus sp., and Sacharomyces cerevisiae, were taken at various stages from a range of fermentation processes and stained with one of three mixtures of fluorescent stains: rhodamine 123/propidium iodide, bis-oxonol/propidium iodide, or bis-oxonol/ethidium bromide/propidium iodide. An individual cell's physiologic state was assessed with a Coulter Epics Elite analyzer based on the differential uptakes of these fluorescent stains. RESULTS: It was possible to resolve an individual cell's physiologic state beyond culturability based on the functionality of dye extrusion pumps and the presence or absence of an intact polarized cytoplasmic membrane, enabling assessment of population heterogeneity. This approach allows the simultaneous differentiation of at least four functional subpopulations in microbial populations. CONCLUSIONS: Fluorescent staining methods used in our laboratories have led to a functional classification of the physiological state of individual microbial cells based on reproductive activity, metabolic activity, and membrane integrity. We have used these techniques extensively for monitoring the stress responses of microorganisms in such diverse areas as bioremediation, biotransformation, food processing, and microbial fermentation; microbial fermentation is discussed in this article.

Cell Physiological Phenomena↗
PubMedDate not supplied

Efficient recognition of protein fold at low sequence identity by conservative application of Psi-BLAST: application.

Based on a study involving structural comparisons of proteins sharing 25% or less sequence identity, three rounds of Psi-BLAST appear capable of identifying remote evolutionary homologs with greater than 95% confidence provided that more than 50% of the query sequence can be aligned with the target sequence. Since it seems that more than 80% of all homologous protein pairs may be characterized by a lack of significant sequence similarity, the experimental biologist is often confronted with a lack of guidance from conventional homology searches involving pair-wise sequence comparisons. The ability to disregard levels of sequence identity and expect value in Psi-BLAST if at least 50% of the query sequence has been aligned allows for generation of new hypotheses by consideration of matches that are conventionally disregarded. In one example, we suggest a possible evolutionary linkage between the cupredoxin and immunoglobulin fold families. A thermostable hypothetical protein of unknown function may be a circularly permuted homolog to phosphotriesterase, an enzyme capable of detoxifying organophosphate nerve agents. In a third example, the amino acid sequence of another hypothetical protein of unknown function reveals the ATP binding-site, metal binding site, and catalytic sidechain consistent with kinase activity of unknown specificity. This approach significantly expands the utility of existing sequence data to define the primary structure degeneracy of binding sites for substrates, cofactors and other proteins.

Algorithms↗
PubMedDate not supplied

Application of the low-loss scanning electron microscope image to integrated circuit technology. Part 1--Applications to accurate dimension measurements.

Scanning electron microscopes (SEMs) are the most extensively used tools for dimensional metrology and defect inspection for integrated circuit technologies with 180 nm and smaller features. Currently, almost all SEMs are designed to collect as many secondary and backscattered electrons as possible. These signals are mainly secondary electrons (SE1, SE2, and SE3) detected with various detection schemes. To facilitate the electron collection, very strong electric and magnetic fields are applied not just in the path of the primary electron beam but to the emerging electrons as well. These new systems provide strong signals, thus better signal-to-noise ratio, and thus resulting in higher throughput than older ones. On the other hand, the use of secondary electrons means that measurement results are much more prone to the detrimental effects of electron beam interactions, sample charging, and sample contamination than measurements with higher-energy backscattered electrons. The use of backscattered electrons, especially low-loss electrons (LLE), can provide better surface sensitivity, edge accuracy, and repeatability, possibly at the expense of measurement speed. This two-part study investigates the benefits and drawbacks of low-loss electron imaging to edge characterization for dimensional metrology and enhancement of fine surface features done through filtration or separation of the generated LLE signal and the use of energy-dependent signals. Part 1 reviews and illustrates the potential for accurate dimensional measurements at low accelerating voltage by LLE, and Part 2 will concentrate on the enhancement of surface features in chemical-mechanically planarized specimens with the use of a novel LLE detector.

Journal Article↗
PubMed1996

High-performance liquid chromatographic resolution of NADP+ after induction of fluorescence and its application to assay for an NADPH-dependent enzyme: application to the determination of glutathione reductase activity in plant leaf extracts.

A method is described for the determination of glutathione reductase activity (GR; EC 1.6.4.2) in plant extracts utilizing HPLC quantitation of NADP+ following the reduction of glutathione disulfides. After protein incubation, fluorescence of NADP+ was induced under strongly basic conditions, and the product was directly resolved from the reaction medium by isocratic reversed-phase elution on a silica-coated alumina support which took 2 min. The mobile phase was acetonitrile-water (50:50) delivered at a flow rate of 1.5 ml/min. The adduct (stable for at least 7 days) was detected fluorometrically and quantitated by direct integration of peak area.

Chromatography, High Pressure Liquid↗
PubMed1999

The Constant Capacitance Model and Variable Ionic Strength: An Evaluation of Possible Applications and Applicability.

Surface complexation models are very successful in describing acid-base properties of minerals in electrolyte solutions. Among these models, the constant capacitance model (CCM) was originally restricted to high ionic strength as a limiting case of a more comprehensive framework. More recently it has been applied to lower ionic strength as well. The present paper shows that a high DeltapK(a) along with a relatively low capacitance value allows the description of the nonlinear charging curves obtained at low ionic strength. However, it becomes evident that the capacitance values are in those cases not in agreement with the more comprehensive picture of the solid-electrolyte interface. With the constant capacitance in the CCM taken as the overall capacitance in that picture it is concluded that the capacitance values obtained in this study from fitting literature surface charge data as well as many published CCM capacitance values are too high to be physically reasonable. Even for situations promoting lower overall capacitance values it had to be concluded that the CCM should be considered as a data fitting model without mechanistic background. Experimentally, the presence of a diffuse layer is at low ionic strength clearly demonstrated in published force measurements between mineral surfaces. In rare cases such measurements indicate that even at 0.1 M the use of a CCM is not at all in agreement with experimental evidence. An exception may be cases where linear charging curves are experimentally found, since such examples (typically found at high ionic strength) may a priori justify the use of a constant capacitance. This exception is allowed accepting linear surface potential-pH relationships reported in the literature. Copyright 1999 Academic Press.

Journal Article↗
PubMed2003

Clinical application of drug pump for spasticity, pain, and restorative neurosurgery: other clinical applications of intrathecal baclofen.

Intrathecal baclofen has been successfully used for control of severe spasticity. Baclofen, an agonist of GABA-B receptor, has other potential effects on pain and recovery from coma. Sporadic episodes of dramatic recovery from persistent vegetative state are reported after intrathecal administration of baclofen. There are also reports on the use of baclofen for neuropathic pain including post-stroke central pain syndrome. Baclofen is also used for control of dystonia due to cerebral palsy or reflex sympathetic dystrophy. On the other hand, epidural spinal cord stimulation has been used for pain, spasticity, dystonia, or attempt to improve deteriorated consciousness, though the effects seem variable and modest. Similarity between baclofen and spinal cord stimulation is interesting in that both involves in spinal GABAergic system. The GABAergic system in the spinal cord plays a pivotal role in various clinical effects of these procedures.

Baclofen↗
PubMed1980

Variations in percutaneous absorption of testosterone in the rhesus monkey due to anatomic site of application and frequency of application.

This study determines if the anatomic region affected percutaneous absorption in the rhesus monkey, an animal model with some relevance to man. Percutaneous absorption of testosterone (13.3 microgram/cm2) from the ventral forearm was 8.8 +/- 2.5%. Absorption from the chest was slightly less (5.3 +/- 0.6%) while that from the cheek was about the same (9.6 +/- 0.2%). Absorption from the scalp was greatly increased (20.4 +/- 2.7%), that from the vagina was the greatest (63.1 +/- 2.6%). As previously noted in man, anatomic variation in skin absorption exists in the rhesus. The ratio of scalp absorption to ventral forearm absorption in the rhesus was similar to that in man. The next objective was to determine the percutaneous absorption of testosterone when applied as a single dose or on a repetitive basis. There was no substantial difference in total absorption when 13.3 microgram/cm2 was applied as a single dose or when the 13.3 microgram/cm2 was applied three times, totaling 40 microgram/cm2. However, when 40 microgram/cm2 was applied as a single dose, absorption was substantially increased over 13.3 microgram/cm2 applied either once or three times. These results confirm previously reported results done with single versus repetitive doses of hydrocortisone.

Animals↗
PubMed1992

Application of polyuronides for removing heavy metals from vegetable oils. III. Application of alginic acid, pectic and pectinic acids for demetalization of hydrogenated sunflower oil.

Laboratory experiments have been carried out for the removal of heavy metals from hydrogenated vegetable oils using hydrated polyuronides (degree of swelling from 4 to 12.8 ml/g) such as alginic acid, pectic and pectinic acids. The effect of the type of polyuronide, degree of esterification and oil treatment on the degree of demetalization has been studied. It has been shown that with increase in the degree of esterification of the polyuronide the efficiency of demetalization decreases. The second and third treatment of the hydrogenated oil with pectinic acid resulted in a high degree of heavy metal removal. The possibility of efficient demetalization of hydrogenated oils by treatment with water solutions of pectinic acids has also been demonstrated. The degree of metal ion removal increases with decreasing concentration of pectinic acids in the water solution.

Adsorption↗
PubMed1994

Digital video applications in radiologic education: theory, technique, and applications.

Computer-assisted instruction (CAI) has great potential in medical education. The recent explosion of multimedia platforms provides an environment for the seemless integration of text, images, and sound into a single program. This article discusses the role of digital video in the current educational environment as well as its future potential. An indepth review of the technical decisions of this new technology is also presented.

Computer-Assisted Instruction↗
PubMed2005

Thought for application and application with thought: issues in theoretical thinking and practical wisdom.

Both theoretical thinking and practical wisdom are used by health professionals in their clinical practice. Lately, discussion has centered on the abstract phrase "theory-practice gap." The health profession is not the only discipline that seeks unity in theory and practice issues. Education is also building bridges in this arena. One reoccurring myth is the notion that theory and practice are separate; as a result, this gives a mistaken impression that theory serves no purpose in practice. Discussion of the issues in this paper includes definitions of theoretical thinking and practical wisdom, theoretical and practical knowledge development, and relevance to health professional's education, practice and science. These issues must be communicated to practitioners, educators and theorists. A collective definition to begin communication is proposed and suggestions are offered for addressing key issues.

Health Knowledge, Attitudes, Practice↗