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At least 541 records · Page 30Linked to original sources
PubMed1981

The hagfish slime gland: a model system for studying the biology of mucus.

The hagfish slime gland may provide a model system for studying certain aspects of the biology of mucus. Mucus is obtained in nonhydrated form by electrically stimulating the anesthetized hagfish and the secretions are stirred into ammonium sulfate. Centrifugation and filtration are than used to isolate the two major secretory products, mucous vesicles and threads. Specific advantages of the model and potential applications for research are discussed.

Animals↗
PubMed1994

The Neuman Systems Model as applied to the terminally ill client with pressure ulcers.

Nursing practice can be enhanced by using a systems approach to the client with multifaceted health problems. The Neuman Systems Model, based on the conceptual framework of stress and reaction to stressors, provides a framework for organizing a holistic approach to the nursing care needs of the terminally ill client with pressure ulcers.

Holistic Health↗
PubMedDate not supplied

Home infusion service delivery system model: a conceptual framework for family-centered care in pediatric home care delivery.

The Home Infusion Service Delivery System model is presented as a conceptual framework for the delivery of pediatric home care. This bicycle-shaped model provides important insights into the interrelationships of available resources for parents seeking home health care for their child. The model is based on nine key elements of family-centered care. Discussions of the model identify the roles and relationships among the family system, four interdependent service delivery systems, the physician, and a total quality management program that coordinates the health care delivery for the child. Examples focus on the delivery of pediatric home infusion therapy. By supporting the family as the primary care giver, this model provides a better fit between consumer need and service delivery.

Community Health Nursing↗
PubMed1986

Reticulomyxa: a new model system of intracellular transport.

Reticulomyxa is a large multinucleated freshwater protozoan that provides a new model system in which to study intracellular transport and cytoskeletal dynamics. Within the cell body and reticulopodial network, rapid, visually striking saltatory organelle motility as well as bulk cytoplasmic streaming can be readily observed. In addition, the cytoskeletal elements within these strands undergo dynamic splaying and fusing rearrangements, which can be visualized by video-enhanced light microscopy. A reactivatable lysed cell model has been developed that appears to preserve, and therefore permits examination of, these three forms of motility in a more controlled environment. Individual organelle movements are microtubule-based and have similarities to, but also differences from, the recently described kinesin-based transport. This lysed cell model can be further manipulated to provide native, ordered, completely exposed networks of either microtubules or microfilaments, or a combination of both, and thus may serve as a versatile motility assay system in which to examine the movement of exogenously added isolated organelles or latex beads.

Actin Cytoskeleton↗
PubMed2003

Technologies to support the creation of complex systems models--using StarLogo software with students.

Research on complex, adaptive systems has made significant advances in recent years in the study of natural and social phenomena that exhibit random variation and selection, resulting in learning or evolution. Unfortunately, students (including K-12, undergraduate and graduate) in most biology programs have little opportunity to explore complex systems during the course of their studies. StarLogo and the Adventures in Modeling Curriculum [Adventures in Modeling: Exploring Complex, Dynamic Systems with StarLogo. Teachers College Press, New York] provide an easily accessible entry point into complex systems modeling for students and other novice modelers. These specialized tools can provide powerful insights into the dynamics of systems and create opportunities to explore challenging and meaningful domains in the biological sciences. Specific applications to epidemiological and ecological systems are explored, including the often debated topic of the evolution of reduced attack rates in predator-prey systems.

Animals↗
PubMed2005

Complex systems model of fatigue: integrative homoeostatic control of peripheral physiological systems during exercise in humans.

Fatigue is hypothesised as being the result of the complex interaction of multiple peripheral physiological systems and the brain. In this new model, all changes in peripheral physiological systems such as substrate depletion or metabolite accumulation act as afferent signallers which modulate control processes in the brain in a dynamic, non-linear, integrative manner.

Electromyography↗
PubMedDate not supplied

The Neuman Systems Model: application in a Canadian HIV setting.

In healthcare research, education and practice there is evidence of a paradigm shift away from disease and illness towards an emphasis on wellness and health. The Neuman Systems Model (NSM) is a nursing model that has been used in a variety of settings with individuals, families and communities. The focus of this model on the prevention of illness and the promotion of health is congruent with the paradigm shift that has occurred in all areas of health care. A review of the literature revealed limited information on the use of nursing models in the clinical area of human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS). This article describes the application of the NSM in an HIV practice setting with reference to the current and future trends in health care in Canada.

Canada↗
PubMed2004

Pegylated polystyrene particles as a model system for artificial cells.

Pegylated polystyrene particles (PS-PEG) were prepared as a model system for artificial cells, by modification of carboxyl polystyrene particles (PS-COOH) with homo- and hetero-bifunctional polyethylene glycols (PEG, MW 1500, 3400, and 5000) containing an amino end group for immobilization and an amino, hydroxyl, or methoxy end group that is exposed at the surface after immobilization. Protein adsorption from human plasma dilutions (85 v %) onto PS-PEG with a PEG surface concentration higher than 40 pmol/cm2 was reduced up to 90-95% compared with protein adsorption onto PS-COOH with a final protein surface concentration of approximately 30 ng/cm2. Two-dimensional gel electrophoresis analyses showed that 30% of the total amount of adsorbed proteins onto PS-PEG are dysopsonins (i.e., nonadhesive proteins like albumin and apolipoproteins). For PS-COOH, <15% of the amount of adsorbed proteins are dysopsonins. In addition, the generation of terminal complement compound (TCC) by PS-PEG particles with a PEG surface concentration lower than approximately 55 pmol/cm2 is not significant. The low protein adsorption, the relatively high percentage of adsorbed dysopsonins, and the low level of complement activation may prevent the uptake of PS-PEG by the mononuclear phagocytic system (MPS) in vivo. Moreover, PS-PEG (PEG surface concentration > approximately 35 pmol/cm2) shows minimal interaction with cultured human umbilical vein endothelial cells (HUVEC), which mimics the endothelial lining of the blood vessel wall.

Adsorption↗
PubMedDate not supplied

Vocational services for traumatic brain injury: treatment definition and diversity within model systems of care.

OBJECTIVE: To examine characteristics and diversity among vocational treatment services in model programs for traumatic brain injury (TBI) rehabilitation. SETTING: Vocational or postacute treatment components of 16 TBI Model System (TBIMS) centers. PARTICIPANTS: Vocational director/coordinator from each TBIMS surveyed in semistructured phone interview. MEASURE: Survey of vocational services for people with TBI, with about 100 closed and open-ended questions on vocational assessments; pre- and postjob placement treatments; program philosophies; funding; and integration of cognitive, behavioral, family, and medical rehabilitation interventions. RESULTS: Great diversity was found among the vocational services of the 16 TBIMS. Programs fell into 3 clusters emphasizing medical rehabilitation services, supported employment, or a combination of these with an emphasis on case management. Job coaching was identified as a key intervention, but there was great variability in intensity, availability, and funding of coaching services. CONCLUSION: Diversity in vocational services appears related to funding differences and "parallel evolution" rather than strong treatment philosophy or scientific evidence base. Multicenter research on effectiveness or establishment of best practices in vocational rehabilitation after TBI must deal with substantial existing variability in treatment models and specific interventions, and must examine the relationship of treatment variations to case-mix factors.

Brain Injuries↗
PubMed1989

A model system for assessing physicochemical factors affecting calcium absorbability from the intestinal tract.

An in vitro model system was utilized to critically examine physicochemical factors that could play a role in determining the amount of potentially absorbable ionic calcium as well as soluble complexes in the proximal jejunum following ingestion of tricalcium dicitrate, calcium carbonate, or tricalcium diphosphate. The solubility of calcium salts (500 mg calcium each) was tested in 300 ml water containing varying amounts of hydrochloric acid (0, 0.72, 2.4, 7.26, and 24.2 mEq) intended to mimic achlorhydric to peak acid secretory states. Whereas 20% of calcium citrate dissolved in the absence of hydrochloric acid, a negligible amount of calcium carbonate and calcium phosphate underwent dissolution. In solutions containing 0.72-7.26 mEq hydrochloric acid, calcium citrate was more than twofold soluble than calcium carbonate, and calcium phosphate had intermediate solubility. At simulated peak acid secretion, all three salts were completely soluble, or nearly so. To simulate pancreatic bicarbonate secretion, the filtrates obtained from solubility studies were titrated to pH 5, 6, and 7 with sodium hydroxide. Reprecipitation of calcium citrate and calcium carbonate did not occur. However, substantial calcium phosphate reprecipitation took place especially at high pH and in filtrates derived from high hydrochloric acid content. In filtrates derived from reprecipitation experiments (at pH 6 and 7), anionic complexation of calcium was calculated in order to estimate the amount of ionic and complexed calcium. Considerable amount of calcium from dissolved calcium citrate was complexed (60-65%), principally as soluble CaCit-, whereas calcium complexation was negligible in the calcium carbonate and calcium phosphate systems.

Anions↗
PubMed1986

Formation of mutagens by heating foods and model systems.

We have demonstrated that the pyrolysis products of amino acids and proteins in model systems are mutagenic. The mutagenic principles in the pyrolyzates of amino acids have been isolated and identified by Sugimura et al. We have isolated and identified amino-alpha-carbolines from pyrolyzed soybean globulin as mutagens. The yield of mutagens by the heating of food constituents is changed by the heating method. Effects of heating methods on the yield of amino-alpha-carbolines were studied in a series of experiments, and the results are shown in this paper. Additionally, it has been shown that by the heating of creatine-sugar mixtures imidazoquinoline or quinoxaline mutagens are formed.

Animals↗
PubMed1993

The role of interleukin-1 alpha in the pathogenesis of periapical bone destruction in a rat model system.

To identify the mediators that stimulate periapical bone resorption following infection, a rat model system was used in which active (rapid) and chronic (slow) phases of bone destruction can be distinguished. Extracts of inflammatory tissues from active lesions contained high levels of bone-resorbing activity, which was destroyed by proteinase K and heat (70 degrees C), but was unaffected by polymyxin B, indicating the presence of protein mediator(s) rather than lipopolysaccharide. Fast-performance liquid chromatography gel filtration of extracts of active lesions demonstrated that most activity was associated with macromolecules of MW 30-60 kDa and 15-20 kDa, consistent with bone resorptive cytokines, including interleukin 1 (IL-1) and tumor necrosis factor (TNF). Inhibition with cytokine-specific antisera demonstrated that resorbing activity in active lesions was significantly neutralized by anti-IL-1 alpha, whereas anti-IL-1 beta, anti-TNF alpha and anti-TNF beta had only slight effect. A lower amount of resorbing activity was present in extracts of chronic lesions, which was also neutralized only by anti-IL-1 alpha. Inflammatory tissue explants produced more IL-1 alpha than IL-1 beta in vitro, confirming findings with extracts, and high levels of IL-1 alpha were present in active lesions by radioimmunoassay. These data indicate that bone resorption stimulated by bacterial infection is primarily mediated by IL-1 alpha in this model. The similarity of cytokines in active and chronic lesions suggests that quantitative rather than qualitative differences in these mediators may account for lesion progression.

Alveolar Bone Loss↗
PubMed1990

Physical properties of single phospholipid bilayers adsorbed to micro glass beads. A new vesicular model system studied by 2H-nuclear magnetic resonance.

Spherical supported vesicles (SSVs), a new model system consisting of single dimyristoyl phosphatidylcholine (DMPC) bilayers adsorbed to spherical glass beads with a narrow size distribution, were prepared at two different sizes (0.5 and 1.5 microns) and their physical properties were studied by deuterium nuclear magnetic resonance (2H-NMR). Such SSV samples can be prepared at any desired size between 0.3 and 10 microns. The 2H-NMR measurements provide evidence for a strong dependence of the spectra and the transverse relaxation times on the curvature of the SSVs in a diameter range between 0.5 and 1.5 microns. For larger SSVs (1.5 microns diameter) their powder spectra and their calculated oriented spectra are similar to those obtained for multilamellar dispersions of DMPC-d54. The lineshape of the smaller SSVs exhibits a temperature dependence which is not found in multilamellar samples. The SSVs are stable in the liquid crystalline phase over days but irreversibly change to multilamellar vesicles in the gel state. The average thickness of the water layer between the single bilayer and the glass bead surface was estimated by 1H-NMR to e 17 +/- 5 A.

Adsorption↗
PubMedDate not supplied

Strategic planning for a Nursing Information System (NIS) in the hospital setting. Development of a Nursing System Model.

As nursing departments become more involved in automation, strategic planning for computer applications gains importance. Making the switch from manual to automated systems requires an understanding and analysis of the present system. This knowledge allows participants to examine the current information processing routines in relation to how well they support departmental goals. Priorities for projects can be established and alternatives for more efficient and effective information management schemes can be considered. The development of a Nursing System Model to serve this purpose is described. The model provides an overview for planning and identifies data classes created or used in nursing, organized according to the processes which act upon the data during the accomplishment of work activities.

Computer Systems↗
PubMed2001

Using model-system genetics for drug-based target discovery.

The combination of medicinal chemistry and model-organism genetics is emerging as a powerful tool for the discovery and validation of drug targets. Model systems can be used to identify the cognate target for compounds that demonstrate in vivo efficacy but have unknown mechanisms of action. Alternatively, drugs with known cognate targets can be used to probe biochemical pathways in model organisms, revealing new targets and mechanisms within these pathways. In both cases, the availability of human genomic sequence data is opening up new opportunities for accelerating target discovery.

Journal Article↗
PubMed1982

An evaluation of two antigen nonspecific assays for circulating immune complexes using a model system.

Two methods of detecting circulating immune complexes (CIC) in serum, the Protein A-glass fiber filter assay (PA-GFF) and the polyethylene glycol (PEG) insolubilization assay, were compared using a model system of BSA/anti-BSA. Supernatants of the quantitative precipitin curve from extreme antigen excess through antibody excess were tested by both methods. The PEG assay detected soluble CIC in all areas where expected by comparison with the Farr Test; the filter assay did not, although it did detect aggregated globulins quantitatively. The PEG assay detected high levels of CIC in serum of rheumatoid arthritis patients and low levels in normal human serum. Postprandial samples and plasma with heparin or EDTA caused unpredictable increases in results in the PEG assay so that for best results the PEG assay should be run on serum from fasting individuals. PEG insolubilized complexes were analyzed and found to contain expected serum components. A slight modification of the original method was made and tested using two other model complex systems and known CIC-containing sera. The PEG turbidity assay it fast, easy, reproducible, and suitable for quantitating and isolating immune complexes in serum.

Animals↗
PubMed1994

The effect of pH and dissolved oxygen levels on methylation and partitioning of mercury in freshwater model systems.

Radio-labelled mercury, 203HgCl2, was added to water overlying sediment in freshwater model systems. The partitioning of 203Hg between water, sediment and air and the concentration of methyl 203Hg in the water did not differ significantly between systems with a water pH of 5.8+/-0.07 and 6.6+/-0.05. When the systems were made anaerobic and microbial activity was stimulated by the addition of tryptic soybroth (TSB), the level of methyl 203Hg in the water increased by two orders of magnitude. There was also an increase in the concentration of total 203Hg in the water, which was greater than the increase in methyl 203Hg, indicating release of both methyl 203Hg and other 203Hg species from sediment to water. In the systems that were kept aerobic, there was no increase in either total or methyl 203Hg in the water after stimulating the microbial activity with TSB. However, volatilization of 203Hg increased, which was not the case in the anaerobic systems.

Journal Article↗
PubMed1998

Mechanistic Studies on Thiazolidine Formation in Aldehyde/Cysteamine Model Systems.

A mechanism was proposed to elucidate the formation of a thiazolidine in aldehyde/cysteamine model systems. Buffer dramatically promotes thiazolidine formation from formaldehyde and cysteamine. Phosphate tends to stabilize the primary carbocation formed, and this may lead to completion of the cyclization by attack of the amino nitrogen on the activated carbon. Protic solvent, by removing the water molecule, further enhances thiazolidine formation. Redox reaction catalyzed by phosphate ions results in the conversion of thiazolidine to the corresponding thiazoline through hydride transfer.

Journal Article↗