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Results for “quantitative model”

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At least 1,747 records · Page 97Linked to original sources
PubMed1976

Topical hemostatic agents to reduce bleeding from cancellous bone. A comparison of microcrystalline collagen, thrombin, and thrombin-soaked gelatin foam.

In fifty-three dogs microcrystalline collagen, thrombin-soaked gelatin foam, and thrombin powder were evaluated as hemostatic agents when applied to bleeding cancellous surfaces after osteotomy of the greater trochanter using two quantitative models: one, a single osteotomy; the other, a double osteotomy. All three agents significantly reduced bleeding compared with the controls, the microcrystalline collagen being most effective. At three months there was no evidence that microcrystalline collagen and thrombin-gelatin interfered with bone healing after the greater trochanter was reattached with two wires.

Administration, Topical↗
PubMedDate not supplied

[Nonmonotonous metabolic response of mammalian cells and tissues to ionizing radiation].

Changes in the activity of ornithindecarboxylase in various tissues and in the amount of catecholamine in rat hypothalamus by the action of acute and chronic ionizing radiation were studied. A nonmonotonous relationship between the metabolic parameters of animal tissues and cells and the radiation dose was revealed. It was assumed that the nonmonotonous character of the dose-response dependence results from the nonmonotonous time course of the metabolic response to irradiation. It was also assumed that living systems have the property of responding to stress agents by nonmonotonous changes in metabolism. In the case of acute irradiation, this response manifests itself as oscillations of metabolic parameters about the control. The oscillations occur with a particular amplitude and periods, which vary with radiation dose, and damp out with time. As a result, in a fixed time interval, the dose-response curve may be nonmonotonous. Reverse dose-response relationships are also possible. In the case of chronic irradiation, the metabolic and functional parameters oscillate throughout irradiation time, and a modification of the response occurs. A prolong exposure to ionizing radiation causes strong changes in the metabolism of lipids of cell membranes, organelles and chromatin, as well as in the functional properties of some mammalian cells and tissues. The necessity of constructing quantitative models for explaining the nonmonotonous dose-response dependence is discussed.

Animals↗
PubMed2001

[Prediction of retention parameters of explosives by artificial neural network].

The quantitative relationship between the retention parameters and the structure of explosives is discussed. Molecular topological indices are used to represent the structure. Based on the back-propagation algorithm, a quantitative model was established after a training process of a train-set containing 20 explosives being completed. The Sigmoid function was chosen as the transmit function. The retention parameters (log kappa w and S) acted as output vectors, while molecular connecting indices (0 chi, 1 chi, 2 chi) and edge adjacent indices(epsilon) acted as input vectors. The input vectors were normalized in the range of -3-3 and the output vectors were normalized in the range of 0-1. The accuracy of network was 0.5 and the beginning value of studying pace (eta) was 0.2, the momentum factor (alpha) was 0.5. The results showed that the yield model reflected the relationship between the structure and retention index of compounds, and had high accuracy. Most of the relative errors were below +/- 5%.

English Abstract↗
PubMed2003

Coregulation of epidermal growth factor receptor/human epidermal growth factor receptor 2 (HER2) levels and locations: quantitative analysis of HER2 overexpression effects.

Elevated expression of human epidermal growth factor receptor 2 (HER2) is known to alter cell signaling and behavioral responses implicated in tumor progression. However, multiple diverse mechanisms may be involved in these overall effects, including signaling by HER2 itself, modulation of signaling by epidermal growth factor receptor (EGFR), and modification of trafficking dynamics for both EGFR and HER2. Because these processes are so tightly interrelated, the net effect of HER2 overexpression is difficult to reliably attribute to any single particular mechanism. To take an important first step toward dissecting the effects of HER2 overexpression on cell responses in terms of the various specific underlying mechanisms, we have developed and validated a quantitative model of the relevant trafficking processes. We then use our model for successful prediction of EGFR and HER2 level and location changes attributable to HER2 overexpression in 184A1 human mammary epithelial cells expressing a series of HER2 levels by retroviral infection. Model predictions are based on our independent experimental measurement of key trafficking parameters for both EGFR and HER2. In terms of trafficking processes, HER2 overexpression reduces the EGFR internalization rate constant and increases the fraction of EGFR recycled. Consequently, our model successfully predicts that HER2 increases the overall level of activated EGFR by both enhancing its recycling and reducing its internalization, but it increases activated EGFR localization at the cell surface almost solely by its reduction of internalization. Furthermore, the model also successfully predicts the effects of monoclonal antibody 2C4, which interferes with HER2/EGFR heterodimerization, on EGFR and HER2 levels and compartmental locations. We anticipate that this model should ultimately be useful in parsing the relative contributions of direct effects of HER2 via signaling vis-a-vis indirect effects of HER2 via modification of EGFR signaling.

Breast↗
PubMed1992

[Effect of doxycycline on leukocyte adhesion in a multifactorial experiment].

The multifactorial analysis was applied to study the effect of doxycycline on leukocyte adhesion to a plastic within wide ranges of the values of experimental factors such as doxycycline concentrations and magnesium and calcium ions. The data were computer-processed and second-order equations characterizing the influence of the factors on adhesion were derived. It was shown that the effect of the ions on adhesion was non-single-valued; accurate quantitative models describing the ion effect on adhesion were developed when the concentration of doxycycline was changed.

Adhesiveness↗
PubMed1992

[Medical informatics as a complementary method in medical education].

The practice of the decision making at the bed side especially highlights the place to be devoted to medical informatics both at the pre- and post-graduate levels. Still in a relatively recent past, say the 50s-60s, most of the medical educational efforts were delivered when watching and then imitating the medical behaviour of an older physician. The medical educators were aware that besides the formal lessons related to selected chapters of medical textbooks, there were an obvious need for better training in the ability to make sound clinical judgements. If this ability has been considered only as an artful and intuitive process neither subjected to theoretical analysis nor to be captured in a formal quantitative model, now things have changed to such an extent that it becomes broadly shared that a science of medical decision making can be reasonably founded and this threefold: 1) Upon a formulated logic, 2) The probability theory, and 3) A value theory. The first gives the hand to artificial intelligence (AI) technics, the third to medical information data bases dealing either with patients (like in hospital information systems) or with literature like MEDLINE or electronic "cookbooks". Basically the probabilistic theory is based here upon a priori probabilities related to patients informations and data and opens the way to bayesian decision making. After this little summary it is stressed that educational informatics in medicine would appear either very central or very marginal, if not optional.

Computer-Assisted Instruction↗
PubMedDate not supplied

Improved retention and bone-tolmplant contact with fluoride-modified titanium implants.

PURPOSE: The purpose of the present study was to investigate whether a fluoride modification of the titanium surface would have an effect on bone response after implantation. MATERIALS AND METHODS: Titanium-oxide-blasted titanium implants with and without fluoride modification were investigated in a rabbit tibia model. Quantitative analysis of surface roughness, biomechanical interlocking, and in vivo tissue reactions in rabbit bone at 1 and 3 months after placement were compared. RESULTS: The fluoride-modified test implants had a slightly smoother surface (Sa: 0.91 +/- 0.14 microm) than the unmodified control implants (Sa: 1.12 +/- 0.24 microm). Significantly higher removal torque values (85 +/- 16 Ncm vs 54 +/- 12 Ncm) and shear strength between bone and implants (23 +/- 9 N/mm2 vs 15 +/- 5 N/mm2) were measured for the fluoride-modified implants after 3 months. The histomorphometric evaluations demonstrated higher bone-to-implant contact for test implants at 1 month (35% +/- 14% vs 26% +/- 8%) and 3 months (39% +/- 11% vs 31% +/- 6%) after placement. DISCUSSION: Implant surface modification with fluoride may result in morphologic and physiochemical phenomena that are of significance for the bone response. Another possible explanation for the findings in the present study is that a surface modification changes the surface chemical structures to be more suitable for bone bonding. CONCLUSION: Based on the biomechanical and histomorphometric data, the fluoride-modified titanium implants demonstrated a firmer bone anchorage than the unmodified titanium implants. These implants achieved greater bone integration than unmodified titanium implants after a shorter healing time.

Animals↗
PubMed2005

[Transmission of tuberculosis (III)].

Tuberculosis outbreak is defined as group infection more than 20 persons had been infected with tubercle bacilli in Japan, provided one person developed disease is counted as 6 persons had been infected. Outbreak is to be reported compulsory to the Ministry of Health, Welfare and Labor. A total of 365 outbreaks of tuberculosis have been reported in these 10 years during 1994 and 2004. Out of them, large scale outbreak more than 10 persons have developed disease were 41 (11.2%). Results of contact surveys has reported that 0.36% of newly registered smear positive cases had caused tuberculosis outbreak, 1.1% had resulted small scale group infection (5 to 19 persons had been infected), although majority of the bacteriology positive cases didn't infected even one person. To make clear the mode of airborne infection with tubercle bacilli more clearly, the author has discussed the results of quantitative model on droplet nucle infection by Riley RL and others, nosocomial infection of smallpox virus in Germany in 1970, the results of analysis of airflow at the sites of outbreaks at business office and middle school in Japan, and so on. Finally, the author has reviewed the development of research on annual risk of tuberculosis infection in Japan and discussed about the present problems of risk of tuberculosis infection in Japan.

Disease Outbreaks↗
PubMed2005

On the use of computational models for the quantitative assessment of surgery in congenital heart disease.

The surgical repair of congenital heart disease often involves significant modifications to the circulatory tree. Resections, reconstructions, graft insertions and the deployment of implants and biomedical devices have an impact on local and systemic haemodynamics, which may be difficult to foresee or to assess quantitatively by clinical investigation alone. Mathematical models can be employed to visualise, estimate or predict events and physical quantities that are difficult to observe or measure, and can be successfully applied to the study of the pre- and post-operative physiology of cardiovascular malformations. This paper analyses the potentialities of computation fluid dynamics in this respect, outlining the method, its requirements and its limitations. Examples are given of lumped parameter models, axi-symmetric models, three-dimensional models, fluid-structure interaction simulations and multiscale computing applied to total cavo-pulmonary connection, aortic coarctation and aortic arch reconstruction.

Cardiovascular Surgical Procedures↗
PubMed2005

[Epilepsy as a dynamic condition: facilitation and inhibition, establishment and remission].

Epilepsy should not be seen as a stable chronic illness but as a condition that undergoes changes over time, due to antagonistic factors which facilitate or counteract seizures. Some of these are known, and their action can best be observed at onset, when seizure repetition is established or prevented, and at remission, when the decline of the antiepileptic drug therapeutic threshold reflects a fall in the propensity to seizures. A quantitative model is proposed which can explain much of the observed variability.

Anticonvulsants↗
PubMed2005

Functional eicosanoid test and typing (FET) of peripheral blood cells in eicosanoids related diseases.

Monitoring of eicosanoid synthesis in peripheral blood cells has significant potential for improving the diagnosis and therapy of many human diseases. The quantitative relation between concentrations of prostaglandins and leukotrienes is central to the physiologic function of the eicosanoid network. Here we show that this regulation, which we call the functional eicosanoid typing (FET), fluctuates dynamically in individual living blood cells from patients, thereby limiting the accuracy with which concentration circuits of eicosanoids can transfer metabolic information. Using living cells in functional cell testing, we characterised the eicosanoid pattern score (EPS). A novel technique based on binomial errors on lipid mediator partitioning enabled calibration of in vivo biochemical parameters in molecular units. We found that eicosanoid production rates fluctuate over a time scale of about twenty minutes, while intrinsic noise decays rapidly. Thus, biochemical eicosanoid parameters, noise, and slowly varying cellular states together determine the effective FET. These results can form a basis for quantitative modelling of natural eicosanoid circuits in diagnosis of eicosanoid related diseases and design of synthetic ones for the prediction other diseases.

Adult↗
PubMed2002

[Studies on quantitative structure-retention relationships for sulfides on stationary phases of different polarities].

Multiple linear regression (MLR) based on forward stepwise multiple regression techniques was used for predicting gas chromatographic retention index of sulfides after calculating their quantum-chemical parameters. The correlative quantitative model between the retention index (IR) of sulfides on four stationary phases of different polarities and their quantum chemical parameters was built. The results proved the strong predictive power of the models. The root-mean-square error (RMS) of the regression equation was less than 4%.

English Abstract↗
PubMed2006

Accounting for structural properties and nucleotide co-variations in the quantitative prediction of binding affinities of protein-DNA interactions.

We describe a quantitative model for predicting the binding affinity of protein-DNA interactions. The described model is based on templates capable of providing a global representation of the modelled transcription factor (TF) binding sites. Templates can capture non independent nucleotide variations and structural properties present in these sites. Tests carried out on the p50p50 and p50p65 variants of the transcription factor NF-kappa B demonstrate a high correlation between the observed binding affinities and the binding affinities predicted by the templates. Only a small subset of training data spanning the space of the binding sites is required to train the templates.

Animals↗
PubMed1991

Cancer and the dynamics of neurodegenerative processes.

The term neurodegenerative denotes a process rather than a state. In contrast, most research on such disorders, whether clinical or experimental, represents only a slice of time. Their progressive nature is mostly confined to speculation instead of being codified in research protocols. Research on cancer, also a degenerative disease, is much more often framed in terms of process. Part of the difference is accounted for by the impact of quantitative modeling, which enjoys a long history in both basic and clinical cancer research and which originated in attempts to describe and understand tumor development. Analogous questions are posed by neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. Among the issues that modeling could help to clarify are the properties and sources of the age-specific incidence rate, which resembles that for cancer, and the pharmacokinetics governing the toxic products of neurotransmitter metabolism. Neurodegenerative disorders maintain a research advantage because functional measures, mostly inaccessible to cancer investigators, serve as the ultimate index of progression. Their exploitation, however, in longitudinal studies remains inadequate.

Animals↗
PubMed1991

[Assessment of the distribution in the body and the dose on the respiratory tract and organs after single, short-term and long-term inhalation of americium-241].

On the basis of comparison of publications on accidental human intake of americium-241 and animal experimental studies dosimetric characteristics were obtained reflecting the dynamics of accumulation, formation of the dose on the organs and parts of the respiratory tract, as well as of the 24-hour elimination from the organism of the mentioned radionuclide following single, short- and long-term administration of americium-241 from the air. Results were obtained with the use of computers for quantitative modelling of the most complete metabolic transport scheme of americium.

Americium↗
PubMedDate not supplied

Program optimization: a semi-quantitative approach.

The authors describe a quantitative model used to express the relative costs and benefits of alternative approaches to pulmonary prevention. This approach identifies the factors that a program director must consider in planning preventive interventions for respiratory disease of workers.

Cost-Benefit Analysis↗
PubMed1991

B cell abnormalities induced by a mu Ig transgene extend to L chain isotype usage.

We have analyzed the phenotype of B cell populations from mice transgenic for a rearranged Ig mu H chain gene. We find a decrease in the number of B cells in the spleens of these mice. Transgenic B cells have decreased surface levels of both IgM and IgD. The circulating IgM in these mice is 3- to 10-fold enriched in lambda L chains, compared with that in non-transgenic mice. Analysis of IgM-producing hybridomas, from transgenic mice that express the transgene at high levels, demonstrates that this higher lambda frequency is observed in transgene-nonexpressing as well as transgene-expressing hybridomas. A partial loss of L chain isotype exclusion is also noted in these hybridomas, and a significant proportion of primary B cells expressing both kappa and lambda L chains on their surface can be demonstrated. These findings suggest an ability of the transgenic Ig H chain to affect events in B cell ontogeny beyond the H chain locus. Our results support a quantitative model of exclusion for both the H chain alleles and the L chain isotypes.

Animals↗