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PubMed1990

Binding studies using ion-selective electrodes. Examination of the picrate-albumin interaction as a model system.

We are studying the binding of ligands to macromolecules by using ligand ion selective electrodes as transducers. The picrate-bovine albumin interaction is examined in detail as a model system. A picrate ion selective electrode is used to monitor the free picrate concentration directly in the presence of albumin and bound ligand. The binding parameters are estimated and the effect of protein concentration, ionic strength, pH, and temperature is studied. The experimental data are interpreted with a specially designed computer program that performs nonlinear least-squares fitting of the generalized Scatchard model with an infinite number of classes of binding sites directly to the raw potentiometric data. The binding parameters (binding constant and maximum number of ligands that can be bound), the nonspecific binding as well as their standard deviations are estimated by this program. The principles described can be used for the potentiometric study of any ligand-binder interaction.

Electrodes↗
PubMed1995

Substance P induces tumor necrosis factor in an ex vivo model system.

Many studies have shown that tumor necrosis factor (TNF) is a potent soluble mediator of immunoregulation and inflammation. Neuropeptide substance P (SP) has been known to exert significant influence on production of certain inflammatory cytokine by immune cells. Immunopathogenic mechanism underlying the effect of neuropeptide substance P (SP) and the specific amino acid sequence of SP that induces TNF has not been clearly studied. Employing ex vivo and in vitro model systems, we investigated the direct effect of different sequences of SP on TNF secretion by whole blood and separated total mononuclear cells. Aliquots of blood samples (1 ml) or Ficoll-Hypaque-separated total mononuclear cells (1 x 10(6)/ml) were cultured with different concentrations of SP and its sequences (SP 1-4, SP 4-11) or vasoactive intestinal peptide (VIP) for 24 hr at 37 degrees C. Plasma samples and culture supernatants were assayed for TNF levels in a bioassay using a TNF-sensitive WEHI 164 subclone 13 cell line. Plasma from blood samples or lymphocytes treated with whole SP and SP 4-11 at 10(-7), 10(-8), and 10(-9) M concentrations induced significant production of TNF compared to negligible levels of TNF produced by SP 1-4-treated and untreated cultures. VIP at all concentrations tested did not induce TNF production and was similar to untreated control cultures. Separated mononuclear cells also produced significant levels of TNF in response to SP and SP 4-11. Anti-TNF-alpha antibodies neutralized the TNF induced by SP 4-11 in plasma. These studies suggest that an ex vivo system using whole blood may be an ideal model to study the effects of SP on TNF production. These studies also demonstrated that the TNF inducing activity of SP residues in the region containing amino acids 4 to 11.

Adult↗
PubMed1990

The Health-Promoting Self-Care System Model: directions for nursing research and practice.

In an effort to theoretically integrate perspectives of self-care and health promotion, the Health-Promoting Self-Care System Model is proposed as a framework for identifying and explaining sequential patterns among factors which influence the decision-making, performance and outcomes of health-promoting lifestyles. The model is based upon a synthesis of elements comprising constructs of the Self-Care Deficit Nursing Theory as well as certain factors in the Interaction Model of Client Health Behaviour and the Health Promotion Model. Directions for research and practice provided by the model should encourage the development of a cumulative nursing knowledge base and contribute to the goal of enhancing the health and well-being of persons across developmental and sociocultural contexts.

Health Promotion↗
PubMed1993

Anoxia-tolerant hepatocytes: model system for study of reversible metabolic suppression.

Chrysemys picta bellii is well known for its ability to survive extended anoxic periods and has been widely used as a model system to study anoxic metabolism. Described here is a method for the isolation of anoxia-tolerant hepatocytes from this species. Freshly isolated hepatocytes were determined to be viable based on trypan blue exclusion, gluconeogenic capacity from [14C]lactate, responsiveness to epinephrine and glucagon, and maintenance of cellular adenylate concentrations. Under anoxic conditions for 10 h there was no significant increase in cell staining and no decrease in cellular ATP concentration. Furthermore, the addition of cyanide at the 5-h mark did not result in any significant differences in these parameters; however, iodoacetate added at this time caused trypan blue staining to increase and ATP concentrations to fall. The rate of glucose production from the cells was threefold greater under anoxic than normoxic conditions, underscoring the important role of the liver in supplying substrate during anoxia. From the rate of O2 consumption and rate of lactate production under anaerobic conditions, ATP turnover rates were calculated to be 68.4 +/- 7.2 and 6.5 +/- 0.43 mumol ATP.g-1.h-1, respectively; this corresponds to a 90% decrease in metabolic rate during anoxia. Within a cellular system such as this the more complex regulatory mechanisms involved in a large coordinated reduction in metabolism can be probed.

Adaptation, Physiological↗
PubMed2000

Membrane fusion activity of tick-borne encephalitis virus and recombinant subviral particles in a liposomal model system.

We present a kinetic analysis of the membrane fusion activity of tick-borne encephalitis (TBE) virus and TBE-derived recombinant subviral particles (RSPs) in a liposomal model system. Fusion was monitored using a fluorescence assay involving pyrene-labeled phospholipids. Fusion was strictly dependent on low pH, with the optimum being at pH 5.3-5.5 and the threshold at pH 6.8. Fusion did not require a protein or carbohydrate receptor in the target liposomes. Preexposure to low pH of the virus alone resulted in inactivation of its fusion activity. At the optimum pH for fusion and 37 degrees C, the rate and extent of fusion were very high, with more than 50% of the virus fusing within 2 s and the final extent of fusion being 70%. Lowering of the temperature did not result in a significant decrease in the rate and extent of fusion, suggesting that TBE virus fusion is a facile process with a low activation energy, possibly due to the flat orientation of the E glycoprotein on the viral surface facilitating the establishment of direct intermembrane contact. The fusion characteristics of TBE virus and RSPs were similar, indicating that RSPs provide a reliable and convenient model for further study of the membrane fusion properties of TBE virus.

Animals↗
PubMed2005

Formation of acrylamide in a processed food model system, and examination of inhibitory conditions.

Acrylamide (AAm) is formed from asparagine (Asn) and reducing sugar during cooking of foods at high temperature. We examined the formation of AAm in a model system using a glass fiber filter paper, and looked for suitable conditions for inhibiting AAm formation. In frying, the formation rate was about 10 times that in a moistureless oven. Increase of frying temperature and frying time increased AAm formation when the residual moisture was 5% or less. AAm increased with increasing amount of glucose (Glc) addition up to 1:1 with respect to Asn, but then decreased. On the other hand, in the case of fructose, as the amount added was increased, AAm increased accordingly. The AAm formation rate with respect to Asn increased when valine (Val) was co-present in a Glc and Asn reaction system. Cysteine and lysine inhibited the AAm formation rate. Pathways for the formation of AAm are proposed.

Acrylamide↗
PubMed2004

A management information system model for process-oriented health care.

OBJECTIVE: To develop a conceptual model of a management information system for process-oriented health care organizations. METHODS: Qualitative data was collected from two case studies in process-oriented health care settings. The first study addressed the information requirements of health care managers and the second study focused on organizational activities and clinical practice. From these data, preliminary models were iteratively developed, interpreted, and further revised. SETTING: A county hospital in southern Sweden with 30 clinics and 3,200 employees. RESULTS: A conceptual model of a management information system for process-oriented health care organizations was developed in two parts: one part that describes the organizational interface of the model and the other part that describes the architecture of the model. CONCLUSION: A conceptual model has been developed for local-level integration of management information systems and organizational procedures in process-oriented health care organizations

Delivery of Health Care↗
PubMed2002

Oligonucleotide arrays for high-throughput SNPs detection in the MHC class I genes: HLA-B as a model system.

A simple and efficient oligonucleotide array was developed to identify single nucleotide polymorphisms (SNPs) encoded within the highly polymorphic human major histocompatibility complex (MHC) using HLA-B as a model system. A total of 137 probes were designed to represent all known polymorphisms encoded in exons 2 and 3. PCR products were amplified from human genomic DNA and allowed to hybridize with the oligonucleotide array. Hybridization was detected by fluorescence scanning, and HLA-B alleles were assigned by quantitative analysis of the hybridization results. Variables known to influence the specificity of hybridization, such as oligonucleotide probe size, spacer length, surface density, hybridization conditions, and array uniformity and stability were studied. The efficiency and specificity of identifying HLA-B SNPs using the oligonucleotide arrays was evaluated by blinded analysis of 100 samples from unrelated individuals representing all HLA-B phenotypes. The oligonucleotide array method described in this paper provides unambiguous detection of complex heterozygous SNP combinations. This methodological approach may be applied to other highly polymorphic gene systems.

Alleles↗
PubMed1991

Molecular behavior of water in a flour-water baked model system.

The molecular behavior of water in complex food systems, via bonding and solvation reactions with low molecular weight solutes or high molecular weight macromolecules, is intimately linked with both the palatability and storage stability of those systems. Due to the difficulty in interpreting data derived from multicomponent finished food products, water behavior in a baked flour-water "matzo" model system was studied. Water behavior was assessed from high resolution [1H] nuclear magnetic resonance (NMR) spin-spin relaxation studies and differential scanning calorimetric (DSC) measurements of unfreezable water content. The unfreezable water capacity of "matzo" model crackers, as measured by DSC, ranged from ca. 24-30% (w/w). These results were corroborated by NMR data. Only one exponent (less than 0.46 msec greater than) is required to fit spin-echo evolution curves below a total moisture content of ca. 20% (w/w), whereas two exponents (less than 0.46 greater than and 1.6 msec) are observed when the moisture content exceeds 20% (w/w). Expert sensory texture assessments parallel unfreezable (= total) water contents between 2.9% (w/w) and 20.1% (w/w). This relationship may be explained by the known tendency for water to plasticize biological polymers, e.g. wheat starch and proteins, and to render these macromolecules incrementally more mobile with increasing water concentration. The similarities (if any) between water of plasticization, immobile water, and "bound" water are discussed, in terms of theoretical physicochemical "states" of water and the various techniques utilized to assess (define) those "states."

Chemical Phenomena↗
PubMed2002

(57)Fe Mössbauer isomer shifts of heme protein model systems: electronic structure calculations.

We report the results of density functional theory (DFT) calculations of the (57)Fe Mössbauer isomer shifts (delta(Fe)) for a series of 24 inorganic, organometallic, and metalloprotein/metalloporphyrin model systems in S = 0, (1)/(2), 1, (3)/(2), 2, and (5)/(2) spin states. We find an excellent correlation between calculation and experiment over the entire 2.34 mm s(-1) range of isomer shifts: a 0.07-0.08 mm s(-1) rms deviation between calculation and experiment (corresponding to 3-4% of the total delta(Fe) range, depending on the functionals used) with R(2) values of 0.973 and 0.981 (p < 0.0001). The best results are obtained by using the hybrid exchange-correlation functional B3LYP, used previously for (57)Fe Mössbauer quadrupole splittings and (57)Fe NMR chemical shifts and chemical shielding anisotropies. The relativistically corrected value of alpha, alpha(rel), converges with the large basis set used in this work, but the exact values vary somewhat with the methods used: -0.253 a(0)(3) mm s(-1) (Hartree-Fock; HF); -0.316 a(0)(3) mm s(-1) (hybrid HF-DFT; B3LYP), or -0.367 a(0)(3) mm s(-1) (pure DFT; BPW91). Both normal and intermediate spin state isomer shifts are well reproduced by the calculations, as is the broad range of delta(Fe) values: from [Fe(VI)O(4)](2-) (-0.90 mm s(-1) expt; -1.01 mm s(-1) calc) to KFe(II)F(3) (1.44 mm s(-1) expt; 1.46 mm s(-1) calc). Molecular orbital analyses of all inorganic solids as well as all organometallic and metalloporphyrin systems studied reveal that there are three major core MO contributions to rho(tot)(0), the total charge density at the iron nucleus (and hence delta(Fe)), that do not vary with changes in chemistry, while the valence MO contributions are highly correlated with delta(Fe) (R(2) = 0.915-0.938, depending on the functionals used), and the correlation between the valence MO contributions and the total MO contribution is even better (R(2) = 0.965-0.976, depending on the functionals used). These results are of general interest since they demonstrate that DFT methods now enable the accurate prediction of delta(Fe) values in inorganic, organometallic, and metalloporphyrin systems in all spin states and over a very wide range of delta(Fe) values with a very small rms error.

Electrochemistry↗
PubMed2002

[The effect of some medications used in the treatment of cerebrovascular diseases on free radical oxidation in the model systems].

The effect of 5 medications used in the treatment of ischemic brain lesions on free radical oxidation was studied. The efficacy level was evaluated by chemoluminescent changes in the model systems generating active oxygen species and lipid peroxides radicals. The most active antioxidants inhibiting chemo luminescence proved to be mexidol, cavinton, instenon. Piracetam acts less effectively. Actovegin did not practically display any antioxidant activity. Thus, the medications studied have different effect on free radical oxidation, dysregulation of which underlies many neurological diseases i.e. ischemic blood circulation disorders.

Animals↗
PubMed2003

The lateral line of zebrafish: a model system for the analysis of morphogenesis and neural development in vertebrates.

The lateral line of the zebrafish has many of the advantages that made the sensory organs of Drosophila a very productive model system: 1) it comprises a set of discrete sense organs (neuromasts) arranged in a defined, species-specific pattern, such that each organ can be individually recognized; 2) the neuromasts are superficial and easy to visualize, and the innervating neurons are easy to label; 3) the sensory projection is simple yet reproducibly organized. Here we describe some of the tools that can be used to investigate the development of this system, and we illustrate their usefulness with specific examples. We conclude that the lateral line is uniquely suited among vertebrate sensory systems for a molecular, cellular and genetic analysis of pattern formation and of neural development.

Animals↗
PubMed1992

Use of an in vitro absorption model system for predicting sustained release of verapamil.

It is shown that it is possible to characterize sustained release formulations in vitro using not only dissolution data but also an absorption model system. The mean dissolution time (MDT) has been shown to be a suitable parameter for evaluating sustained release formulations in vitro. t1/2 and mean residence time (MRT) have been shown to be convenient pharmacokinetic parameters for characterizing sustained release formulations. For comparing in vitro and in vivo results the quotients MDT normal/MDT retard and MRT normal/MRT retard do seem to be useful.

Adult↗
PubMed2002

The Ustilaginales as plant pests and model systems.

The Ustilaginales are a vast and diverse group of fungi, which includes the plant pathogenic smuts that cause significant losses to crops worldwide. Members of the Ustilaginales are also valuable models for the unraveling of fundamental mechanisms controlling important biological processes. Ustilago maydis is an important fungal model system and has been well studied with regard to mating, morphogenesis, pathogenicity, signal transduction, mycoviruses, DNA recombination, and, recently, genomics. In this review we discuss the life cycles of members of the Ustilaginales and provide background on their economic impact as agricultural pests. We then focus on providing a summary of the literature with special attention to topics not well covered in recent reviews such as the use of U. maydis in mycovirus research and as a model for understanding the molecular mechanisms of fungicide resistance and DNA recombination and repair.

Models, Biological↗
PubMed1990

A three-dimensional model system to study the interactions between human leukocytes and endothelial cells.

Leukocyte adhesion to endothelial cells and migration into the subendothelial matrix was studied with a three-dimensional model system, consisting of human endothelial cells cultured on a loose collagen matrix. We developed a new method to separate the endothelial cell monolayer and adhering leukocytes, from the subendothelial matrix, allowing simultaneous analysis of leukocyte adhesion and transendothelial migration. Monocytes adhered more avidly to untreated endothelial cells than did neutrophils (2.5 +/- 0.3 vs. 1.0 +/- 0.2 leukocytes per endothelial cell). Only a small fraction (10%-20%) of these leukocytes migrated into the subendothelium. Pretreatment of endothelial cells with interleukin 1 (IL 1) enhanced adhesion (20%), but not migration of monocytes. In contrast, neutrophil adhesion was markedly and in a time-dependent manner increased by IL 1 treatment (i.e. 200% after 6 h and 110% after 24 h of IL 1 treatment). Moreover, IL 1 pretreatment enhanced neutrophil migration twofold. Activation of leukocytes with formyl-methionyl-leucyl-phenylalanine (fMLP) enhanced both monocyte and neutrophil adhesion, but did not affect leukocyte migration. Under all conditions, monocyte adhesion was only partly (30%-40%) inhibited by monoclonal antibodies (mAb) against the common beta subunit of the leukocyte-cell adhesion molecules (LeuCAM: CD18) and 25%-30% by mAb against the alpha subunit of LFA-1 (CD11a). In contrast, mAb against the alpha subunits of Mac-1 (CD11b) and p150.95 (CD11c) were hardly effective. fMLP-mediated neutrophil adhesion was reduced to below baseline levels by anti-LeuCAM (CD18) mAb, whereas the LeuCAM contribution in IL 1-mediated neutrophil adhesion was less pronounced and varied in time. IL 1-mediated neutrophil migration, however, was completely blocked by anti-LeuCAM mAb. fMLP-mediated neutrophil adhesion was inhibited by mAb against the alpha subunits of Mac, while mAb against the alpha subunits of LFA-1 and Mac-1 both reduced IL 1-mediated adherence. In summary, we describe a novel leukocyte adhesion/migration method and demonstrate that the contribution of the LeuCAM complex in leukocyte-endothelium interaction varies depending on cell type and stimulus used.

Antibodies, Monoclonal↗
PubMed1979

The effect of long-term exposure to cigarette smoke on the height and specificity of the secondary immune response to influenza virus in a murine model system.

The effect of long-term exposure to cigarette smoke on the height and specificity of the secondary humoral immune response to influenza was investigated in a murine model system. It was shown that if mice were pre-immunized with a sub-lethal infection of influenza virus and then exposed to cigarette smoke daily for 36 weeks, they were able to mount a secondary immune response of normal height on subsequent challenge with the homologous virus strain. The response however, was less specific than that elicited in control mice, with high titres of cross-reacting antibody by haemagglutination-inhibition to the following strain in the same antigenic series. Recall of antibody to the previous strain in the antigenic series was not observed in either control or smoke-exposed animals. These results serve to correct an earlier discrepancy between the murine system and human studies in which the response to influenza infection in mice was depressed by prolonged exposure to cigarette smoke, whereas in man the response of smokers did not differ significantly from that of non-smokers. This apparent discrepancy had been caused by a lack of previous experience of influenza in the mice, which had therefore mounted a primary response, compared with the secondary response observed in the human studies.

Animals↗
PubMed1992

Expression of human IL-1 beta in Salmonella typhimurium. A model system for the delivery of recombinant therapeutic proteins in vivo.

The feasibility of using Salmonella typhimurium aroA mutant (SL3261) to deliver protein therapeutic agents was investigated in a murine model system. We have constructed an Escherichia coli expression plasmid designed to express the human protein IL-1 beta. This plasmid expresses IL-1 beta to high levels (greater than 30% total cell protein) in E. coli. In Salmonella the IL-1 beta is expressed constitutively to about 10% total cell protein, as verified by Western blotting analysis using polyclonal rabbit anti-IL-1 beta antibody. The protein is produced in a soluble and biologically active form. BALB/c mice administered orally or i.v. with S. typhimurium aroA mutants carrying the plasmid produced highly significant antibody responses against human IL-1 beta as determined by a solid-phase RIA. Furthermore, mice injected with the construct were significantly protected against lethal gamma-irradiation (850 rad). This study therefore demonstrates that the vaccine strain of Salmonella mutants can also be used effectively to deliver therapeutic proteins in vivo.

Animals↗
PubMedDate not supplied

Reflotron performance in a community screening program: results of the Massachusetts Model Systems for Blood Cholesterol Screening Project.

We evaluated the precision, accuracy, and durability of the Reflotron portable analyzer as part of the National Heart, Lung, and Blood Institute's Model Systems for Blood Cholesterol Screening Program. We conducted screenings in a wide variety of settings in four Massachusetts communities over a 16-month period. Fingerstick samples from 10,428 individuals were tested on the Reflotron at the screening sites. For comparison, we drew venous samples from 972 participants and analyzed them in a reference laboratory, which had met the requirements of the Centers for Disease Control's Lipid Standardization Program. All four Reflotrons tested met the 1988 guidelines for precision and accuracy established by the Laboratory Standardization Panel (LSP) of the National Cholesterol Education Program (NCEP). None of the analyzers consistently met the 1992 LSP standards for precision, although two met the 1992 standards for accuracy. More than 40% of Reflotron values differed from the reference laboratory values by more than 5%. As a consequence, more than 16% of individuals were misclassified in terms of the NCEP risk category into which their Reflotron readings fell. All four instruments malfunctioned at some point during the project, precluding their further usage. We recommend improvements in the precision, accuracy, and durability of this analyzer.

Adult↗