Search

Inverted colloidal crystal geometry has been recently utilized in the design of highly organized 3D cell scaffolds. The regularity of the resulting scaffolds enables computational modeling of scaffold properties. In this work we probe the resistance offered by these scaffolds to nutrient transport, by using Brownian dynamics and Monte Carlo simulations to model the effective nutrient diffusivity. Brownian dynamics simulations indicate that the effective diffusivity for small nutrients in the scaffold, D(eff)=0.3D(0), where D(0) is the free solution diffusivity. Further, results of Monte Carlo simulations for dilute solutions of larger particles show that the D(eff) decreases linearly with the size of the particles.

Spontaneous oscillatory activity is a general feature of developing neural networks. Early in postnatal development, spontaneous network-driven events, termed giant depolarizing potentials (GDPs), occur synchronously over the entire hippocampus. By performing simulation of hippocampal network with using physiology parameters of the neurons and its network from the present experiments and literature dates, we investigated the participation of the different components of network in the generation of GDPs. Comparing the results of the model and in vitro experiments we conclude that are necessary for the GDP generation involvement the activation of GABAergic, glutamatergic inputs and perhaps gap junction.

Purpose: Optoacoustic tomography (OAT) is a novel medical imaging method that uses optical illumination and ultrasonic detection to produce deep tissue images based on their light absorption. Abnormal angiogenesis in advanced tumors, that increases the blood content of the tumor, is an endogenous contrast agent for OAT. In early stages, however, angiogenesis is not sufficient to differentiate a tumor from normal tissue; justifying the application of an exogenous contrast agent. We have developed a molecular based contrast agent composed of gold nanoparticles conjugated to a monoclonal antibody that improves OAT imaging to potentiate its use in imaging deep tumors in early stages of cancer or metastatic lesions., Procedure: Due to their strong optoacoustic signal, we used gold nanoparticles (NPs) as a contrast agent. To target NPs to breast cancer cells, we conjugated NPs to a monoclonal antibody that specifically binds cell surface receptors known to be overexpressed in human breast tumors., Results: In a series of in vitro experiments, Herceptin (monoclonal antibody that binds HER2/neu) conjugated to 40 nm NPs (Mab/NPs) selectively targeted human SK-BR-3 breast cancer cells. The breast cancer cells were detected and imaged by OAT in a gelatin phantom that optically resembled breast tissue. Sensitivity experiments showed that a concentration as low as 10(9) NPs per ml were detectable at a depth of 6 cm., Conclusion: Experimental data together with theoretical analysis demonstrate the feasibility of detection of deeply seeded small tumors that express tumor associated antigens using targeted gold NPs and OAT.

The structure of the multilayer assemblies of yttrium iron garnet nanoparticles (YIG) with polyelectrolytes was investigated with the emphasis on the control of the particle density in the adsorption layers. It was found that the growth of YIG films prepared by the layer-by-layer assembly can occur via two deposition modes: (1) sequential adsorption of densely packed adsorption layers (normal growth mode) and (2) in-plane growth of isolated particle domains (lateral expansion mode). Importantly, the dependence of the optical density on the number of deposition cycles remains linear in both cases. Microscopy results indicate that the origin of the lateral growth is in the interplay of particle/particle and particle/polyelectrolyte interactions rather than in a substrate effect. The lateral expansion mode is a general attribute of the layer-by-layer deposition and can be observed for various aqueous colloids. For the preparation of sophisticated multifunctional assemblies on nanoparticles, the film growth via domain expansion should be avoided, and therefore, one must be able to control the growth pattern. The switch from lateral to normal growth mode can be effected by grafting charged organic groups to YIG nanoparticles. Hydrophobic interactions between the hydrocarbon groups of the modified YIG and polyelectrolyte significantly increase the attractive component of the particle/polyelectrolyte and particle/particle interactions. The films from modified YIG display densely packed nanoparticle layers with a greatly reduced number of defects.

A systemic study of the mechanisms of motor activity of paramecium was carried out. The movements of paramecium responding to various influences were photographed. The analysis of the data revealed the time dependences of the rate of movement, rate of rotation, and the radius and the pitch of the helix trajectory. Mathematical models of the membrane and a unit that transforms the calcium signal to programs of regulating the effectors were constructed. A system of equations for constructing the trajectory of movement was proposed. It is concluded that the biomolecular system that involves calmodulin, calmodulin-dependent ionic channels, adenylate cyclase, guanylate cyclase, phosphodiesterases, Ca(2+)-calmodulin, cAMP, cGMP-dependent protein kinases, and phosphoprotein phosphatases is capable of regulating motor reactions necessary for complex maneuvering of paramecium under various conditions.

A mathematical model of the dynamic behavior of phosphorylase kinase was devised. Based on the results obtained, the function of this protein is discussed. It is suggested that phosphorylase kinase doses in a cAMP-dependent manner additional portions of glucoso-l-phosphate, which the muscle cell receives in response to contraction.

Changes in the central hemodynamics were followed up by echocardiography and the linear velocity of the bloodflow by transcranial dopplerography in 15 patients with ASA classes I-II during induction bolus anesthesia with propofol in a dose 2.7 mg/kg without opioids. The diastolic and mean arterial pressure decreased by 12.3 and 15.4 %, respectively, the rate of cardiac contractions by 7.8%, cardiac index by 13.4%, and the resistive index on the radial and middle cerebral arteries by 13.4 and 10.2%, respectively, after administration of the above dose of propofol. The reaction to intubation of the trachea was the minimal, consisting in an increase of the mean and systolic arterial pressure by 22.2 and 22.7%, respectively, and of diastolic by 16.1%. The rest parameters were as initially. The linear velocity of the bloodflow in the middle cerebral artery did not reliably change. Hence, the central hemodynamic parameters are stable on condition that the deficit in the central bloodflow during induction anesthesia with propofol in a dose of 2.7 mg/kg is compensated for, adequate protection from intubation stress is provided, and autoregulation of the cerebral bloodflow is preserved.

A physical approach to the description of the motion mechanism of cilia based on the importance of hydrodynamical interactions between the intraciliary microstructures is proposed. The motion of the cilium model was investigated theoretically. A mechanism of synchronization of cilia beating in metachronal waves is proposed.

People working in modern carpet industry are exposed to a complex of factors of different origin, the most important among which are general vibration and styrene vapors. It has been found out in animal experiments simulating working conditions, that the central nervous system is the most sensitive both under an isolated and joint exposure to the factors. The joint exposure of animals to styrene and vibration may be evaluated as having different targets depending on the parameters under study.

The results of 44 studies of circulation parameters and blood transport function of 14 test subjects exposed to 7-day bed rest (-10 degrees head-down tilt) and acceleration -4.5 Gz have demonstrated that the blood transport carriers and their actively binding centers form working structures in the adaptive reactions. As compared to the pretest level, the distribution ratio of 14C-adenine between two immiscible phases (plasma/oil, erythrocytes/oil) varies from -12 to 14% on bed rest day 3 to +32 to 40% on bed rest day 7; it increases by 145-150% after exposure to acceleration +4.5 Gz. The parameters of the blood transport function give a quantitative description of its adaptive reactions to environmental effects.

A total of 68 patients with non-specific aortoarteritis (NAA) and the involvement of the aortic arch and its branches were observed. The onset of disease in a young age, a high frequency of cerebro-ischemic disorders and involvement of the other vascular regions, late diagnosis were typical signs. Knowledge of NAA clinical peculiarities, thorough examination of patients using physical and instrumental methods turned out decisive in diagnosis.