Some aspects of biological modelling.
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Animals↗
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Results for “Models, Biological”
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Generating biological models through gene transfer to domestic animals.
Transgenic domestic animals remain infrequently used as models for biochemical, biomedical or pharmaceutical studies. The difficulty in obtaining these animals and the cost of their maintenance explains this situation. This review briefly summarizes the different techniques of gene transfer, targeted or not, and also the techniques for constructing vectors for transgene expression. A few examples of domestic animal models are also reported.
Animals↗
[Biological model of spontaneous progressive vitiligo].
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Animals↗
Symbolic reachable set computation of piecewise affine hybrid automata and its application to biological modelling: Delta-Notch protein signalling.
Hybrid automata are an eminently suitable modelling framework for biological protein regulatory networks, as the protein concentration dynamics inside each biological cell are modelled using linear differential equations; inputs activate or deactivate these continuous dynamics through discrete switches, which themselves are controlled by protein concentrations reaching given thresholds. This paper proposes an iterative refinement algorithm for computing discrete abstractions of a class of hybrid automata with piecewise affine continuous dynamics and forced discrete transitions, defined completely in terms of symbolic variables and parameters. Furthermore, these discrete abstractions are utilised to compute symbolic parametric backward reachable sets from the equilibria of the hybrid automata, that are guaranteed to be exact or conservative under-approximations. The algorithm is then implemented using MATLAB and QEPCAD, to compute reachable sets for the biologically observed equilibria of the multiple cell Delta-Notch protein signalling automaton with symbolic parameters. The results are analysed to show that novel, non-intuitive, and biologically interesting properties can be deduced from the reachability computation, thus demonstrating the utility of the algorithm.
Algorithms↗
A study of the characteristics of single-injection insulated block needles in a biologic model.
BACKGROUND AND OBJECTIVES: Single-injection block needles are manufactured in many different lengths, diameters, and tip designs, but the literature contains no reports of methods to assess clinical characteristics of regional-block needles. A novel animal model for the assessment of the characteristics of single-injection regional anesthesia needles is described. METHODS: Nine different needles designed for peripheral nerve blocks that were fitted with identical hubs were used. Pork bellies were used as the biologic model. The bellies were mounted such that the needles passed from inside to outside. The last layer to be penetrated was the skin. Ten experienced and blinded anesthesiologists scored the feel, resistance, and usability of the 9 needles during their passage through similarly prepared pork bellies. Two identical (index) needles were included in the study to assess the internal validity of the study. RESULTS: The overall scoring was acceptably consistent and repeatable and showed statistically significant differences between the needles tested. The needles that were judged the most usable were those with a moderate resistance to passage through the tissue and a high degree of feel, which was defined as the ability to appreciate the passage of the needle through the tissue planes. Needles with very high or very low resistances and those with poor feel scored poorly on the usability scale. Differences in individuals' assessment of the index needles suggested some within-subject variability during the study. CONCLUSIONS: This type of biologic model can be used for the quantifiable and repeatable assessment of different needle tip designs. Needles with moderate resistance and high feel were preferred.
Animals↗
[Use of a biological model of isolated overload of the skeletal muscle for determination of the effect of anabolic steroids].
The authors tested a new biological model for the quantitative determination of the anabolic effect of steranobols of prolonged action. The principle of the method consists in creation of an isolated overload of the skeletal muscles of the shin (m. soleus and. m. plantaris) following section of the tendons of their synergist--m. gastrocnemius in rats, with the subsequent recording their weight gain caused by the administration of anabolic steroid. The method is simple, sensitive and permits to use the animals of different weight and sex without subjecting them to castration.
Adaptation, Physiological↗
[Effects of weak magnetic poles and water and model biological systems].
The effect of the weak variation magnetic fields on the model biological systems; i.e. the solution of dyes and proteins is investigated. The structural change of these systems under the action of the variation magnetic field of 156.4 Hz and the amplitude of 12.3 A/m was determined by the method of absorbtion and luminescent spectroscopy. It is suggested that this effect realizes through the hypothesis using the method of correlation spectroscopy of scattered light, there have been performed the studies of the structure of water and its changes at different temperatures; on dissolving of non-electrolytes and on exposure to the magnetic field of variable frequency. The accumulated data are indicative of changing the structure of water after the effect of resonance magnetic field. The influence of the weak magnetic fields on the structure of water is due to the clusters which are presented in water and controlled the optical heterogeneity of the medium. The cluster dimensions were evaluated.
Absorption↗
Panic anxiety: a new biological model.
Previously unrecognized similarities among metabolic responses to various maneuvers used to evoke anxiety in patients with panic disorder are described. On the basis of these observations, a new biological model is proposed for panic disorder, in which the primary defect--which is neuroendocrine rather than psychiatric--is operationally placed within the redox-regulating apparatus of the brain stem. This model is consistent with many clinical features of panic disorder and also provides a theoretical framework for further studies of the pathophysiology of this and related conditions (e.g., hyperventilation syndrome).
Anxiety Disorders↗
Investigation of time-gap formulae on the CRE system using mouse tissue as a biological model.
The cumulative radiation effect (CRE) is one of several empirical scalar descriptions of biological effect which enable corrections to be made for gaps in radiotherapy treatment. Predictions of this theory were tested using mouse crypt regeneration and mouse skin as biological models. These experimental results are discussed in terms of the dependence of tissue regeneration potential during a gap on the biological effect achieved before the gap, and on gap length. A hypothesis is proposed to reconcile the apparent conflict between the two experiments. While the simple exponential gap formulation of the CRE is seen to be inadequate, insufficient data are available at present to modify it.
Animals↗
Ferrokinetics: a biologic model for plasma iron exchange in man.
A method is presented for calculating internal iron kinetics. An early reflux associated with extravascular exchange and a late reflux associated with erythropoiesis are described. A biologic model of iron exchange is proposed in which erythron iron turnover is divided into an effective portion (iron fixed in circulating red cells) and wastage iron of erythropoiesis (late reflux). Nonerythroid iron exchange also has a fixed portion (parenchymal uptake) and an early reflux (lymphatic circuit), both of which correlate in amount with the amount of plasma iron. Ferrokinetic measurements in normal subjects and in various pathologic states are presented to validate the model.
Adolescent↗
Childbirth as a biological model for stress? Associations with endocrine and obstetric factors.
OBJECTIVE: The aims of this investigation were to measure corticotropin-releasing hormone (CRH), corticotropin (ACTH) and cortisol before, during and after delivery searching for an endocrine intercorrelation of the hypothalamic-pituitary-adrenal (HPA) axis and to correlate these findings with obstetrical variables. METHODS: Blood was sampled from 50 women with singleton pregnancies at term without uterine contractions, during delivery (after full cervical dilatation) and on the 4th postnatal day. Hormones were measured by radioimmunoassay (RIA). The correlation between obstetric variables, sociodemographic and endocrine data were evaluated using the Spearman rank coefficient. Group comparisons for continuous variables were calculated using the Mann-Whitney U test and Kruskal-Wallis test. RESULTS: Maternal plasma ACTH and cortisol increased significantly during labor, declining toward the 4th postnatal day (p < 0.001) and showing a significant intercorrelation (p < 0.01). Compared to women without uterine contractions CRH rose during labor (p < 0.05) and decreased rapidly to the 4th postnatal day (p < 0.001). No correlations between CRH and ACTH or cortisol were observed. None of the obstetrical variables (parity, newborn's weight, duration of delivery) revealed any significant correlation with ACTH. Analgetic medication (pethidine hydrochloride) was not able to influence the endocrine response to labor stress. CONCLUSIONS: Stressful experience during childbirth has an impact on endocrine response. However, this is not fully evident along the HPA axis in a simple biological model with monocausal dependencies. This 'biological stress model' is not sensitive enough to detect different childbirth conditions and the hormones in the maternal compartment have partially fetal (placental) origin.
Adrenocorticotropic Hormone↗
Influence of sterilization on the mineralization of titanium implants induced by incubation in various biological model fluids.
The aim of this work was to investigate the effect of the sterilization processes on the mineralization of titanium implants induced by incubation in various biological model fluids. Titanium samples were submitted to the following sterilization processes used for implant materials: steam autoclaving, glow discharge Ar plasma treatment and gamma-irradiation. The modification of the treated surfaces was evaluated by contact angle determinations, X-ray photoelectron spectroscopy (XPS), laser profilometry and X-ray diffraction. The most significant modifications were detected on the wettability: while the samples treated with Ar plasma became highly hydrophilic (water contact angle approximately 0 degrees), gamma-irradiation and steam sterilization induced an increase in the hydrophobicity. After being sterilized, the samples were incubated for one week in three biological model fluids: Hanks' Balanced Salt Solution, Kokubo's simulated body fluid (SBF) and a fluid, designated by SBF0, with the same composition of SBF but without buffer TRIS. The level of mineralization of the incubated Ti samples, assessed by dynamic contact angle analysis, scanning electron microscopy, electron dispersive spectroscopy and XPS, indicated that the early stages of mineralization are essentially independent of the sterilization method. In contrast, the incubating fluid plays a determinant role, SBFO being the most efficient medium for biomineralization of titanium.
Biocompatible Materials↗
Biological models of carcinogenesis and quantitative cancer risk assessment.
Biologically-based models of carcinogenesis were originally developed to explain certain quantitative phenomena associated with carcinogenesis, and to provide a framework within which questions regarding the process could be addressed. Some limitations in the use of these models for quantitative cancer risk assessment are discussed.
Animals↗
Cellular immunology in regular dialysis: a biological model for biocompatibility evaluation.
Cellular immunity represents an interesting biological model for biocompatibility evaluation of artificial materials owing to its sensitivity to contact with the external environment and its capability of modulating response reactions to foreign agents. Advanced methodologies such as flow cytometry and the immunoenzyme techniques in particular have given new insights into lymphocyte structure and functions, enabling analysis of the in vivo modification of these cells. By means of these sophisticated techniques we investigated lymphocyte activation and proliferation during one single haemodialysis session. Findings clearly show that increases in HLA antigen density (class I and II), DNA synthesis, and interleukin-2 receptor serum concentration (Il-2R) take place during the dialysis procedure, and reach their maximum during the first hour of extracorporeal circulation. The relationship between dialysis procedure and cellular immunity appears noticeable and is of potential value in the evaluation and quantification of the biocompatibility of different dialysis membranes.
Adult↗
A biological model for the regulation of peri-implantational hemostasis and menstruation.
OBJECTIVE: To delineate the physiologic mechanisms whereby the human endometrium maintains hemostasis during endovascular trophoblast invasion but permits menstrual hemorrhage. METHODS: Experimental results are presented that are relevant to developing a comprehensive biological model for studying peri-implantational hemostasis and menstruation. RESULTS: A marked increase in the expression of tissue factor (TF) and type-1 plasminogen activator inhibitor (PAI-1) and an inhibition of tissue-type and urokinase-type plasminogen activators (tPA and uPA, respectively), matrix metalloproteinases (MMP), and endothelin-1 (ET-1) expression accompany progestin-induced decidualization of estrogen-primed endometrial stromal cells both in vivo and in vitro. The presence of these important regulators of hemostasis, fibrinolysis, extracellular matrix (ECM) turnover, and vascular tone in decidualized human stromal cells and decidual cells isolated from gestational endometrium suggests a mechanism to explain the absence of hemorrhage during invasion of the endometrial vasculature by trophoblasts. Conversely, progesterone withdrawal reduces TF and PAI-1 expression and increases tPA, uPA, MMP, and ET-1 expression accounting for the hemorrhage, enhanced fibrinolysis, ECM degradation, and ischemic spiral arterial vascular injury characterizing menstruation. CONCLUSION: Perivascular decidualized endometrial stromal cells are spatially and temporally positioned to promote endometrial hemostasis during implantation but, paradoxically, promote the hemorrhage of menstruation via their hormone-regulated expression of hemostatic, proteolytic, and vasoactive proteins.
Embryo Implantation↗
Predicting risk of ketosis in dairy cows using in-line measurements of beta-hydroxybutyrate: a biological model.
Automated monitoring of individual cows to determine health status is a potentially valuable management tool, especially in large dairy herds. Herein is described the rationale, structure, and functionality of a biological model to predict risk of ketosis in individual cows using in-line measurements of the ketone body beta-hydroxybutyrate (BHBA) in milk. The model also uses acceleration in milk yield, body fatness at calving, diseases in current lactation, and incidences of ketosis in earlier lactations as additional risk factors for ketosis. However, the model is designed to function merely on the basis of milk BHBA in the absence of other data. Values of milk BHBA are smoothed using a state space model before these are used in calculations in the biological part of the model. The model is designed to be updated each time a new BHBA measurement or a disease occurrence is available and then uses previous and current data. Outputs of the model are the risk of ketosis (value between 0 and 1, where 0 = no risk and 1 = clinical ketosis) and how many days until the next milk sample should be taken and analyzed for BHBA. At higher risks for ketosis, more frequent milk sampling is the recommended output. Test examples from cows for which BHBA has been measured extensively were used to show the functionality of the model. The model performed equally well when reductions in sampling frequency were applied, and it was also relatively robust to the addition of up to +/- 2 residual SD of random noise in the BHBA values. This model has the potential to provide the basis for a useful disease monitoring and management tool. However, thorough validation awaits a much larger dataset and testing of the model under a variety of on-farm situations.
3-Hydroxybutyric Acid↗
Application of high-performance liquid chromatography based measurements of lipophilicity to model biological distribution.
Octanol-water partition coefficients are the most widely used measure of lipophilicity in modelling biological partition/distribution. It has long been recognised that the retention of a compound in reversed-phase liquid chromatography is governed by its lipophilicity/hydrophobicity, and thus shows correlation with an octanol-water partition coefficient. A great number of publications have reported the efforts made to adjust HPLC conditions to measure surrogate octanol-water partition coefficients. However, there is no general consensus in this field. HPLC provides a platform to measure various types of lipophilicity that can provide relevant information about the compounds' property. In this way HPLC can be more valuable than just a surrogate for octanol-water partition. Chromatography using biomimetic stationary phases may provide better insight for biological partition/distribution processes. The research in this field is still ongoing and a large variety of HPLC conditions have been suggested. This review will outline approaches to overcoming the difficulties of standardisation and describe different theoretical approaches for comparison of HPLC lipophilicity data obtained under various conditions, along with the relation of these results to biological partition/distribution.
Chemical Phenomena↗
Structural systems biology: modelling protein interactions.
Much of systems biology aims to predict the behaviour of biological systems on the basis of the set of molecules involved. Understanding the interactions between these molecules is therefore crucial to such efforts. Although many thousands of interactions are known, precise molecular details are available for only a tiny fraction of them. The difficulties that are involved in experimentally determining atomic structures for interacting proteins make predictive methods essential for progress. Structural details can ultimately turn abstract system representations into models that more accurately reflect biological reality.
Cell Physiological Phenomena↗