Homogeneous orthogonal diffusion of drugs in the rat brain.

The study introduced a homogeneous orthogonal diffusion model to describe the diffusion pattern of agents in the rat brain. Magnetic resonance imaging was performed post-injection of paramagnetic drugs into the caudatum of the rat brain at predetermined time intervals. The signal intensity on magnetic resonance images was converted to agents' concentration, and the standard least square method was employed to estimate the diffusion coefficients. The diffusion coefficients calculated along the three orthogonal axes were D1  = (0.0097 ± 0.0036) mm2 /h, D2  = (0.0153 ± 0.0033) mm2 /h, and D3  = (0.0293 ± 0.0155) mm2 /h; the clearance rate constant was k = (0.2177 ± 0.0112)/h. The theoretical homogeneous orthogonal model can enhance our knowledge on both the biophysical characteristics of brain extracellular space and the interstitial drug delivery in the brain.

[Molecular structure and fractal analysis of oligosaccharide].

OBJECTIVE: To propose a calculation method of oligosaccharides' fractal dimension, and to provide a new approach to studying the drug molecular design and activity. METHODS: By using the principle of energy optimization and computer simulation technology, the steady structures of oligosaccharides were found, and an effective way of oligosaccharides fractal dimension's calculation was further established by applying the theory of box dimension to the chemical compounds. RESULTS: By using the proposed method, 22 oligosaccharides' fractal dimensions were calculated, with the mean 1.518 8 ± 0.107 2; in addition, the fractal dimensions of the two activity multivalent oligosaccharides which were confirmed by experiments, An-2 and Gu-4, were about 1.478 8 and 1.516 0 respectively, while C-type lectin-like receptor Dectin-1's fractal dimension was about 1.541 2. The experimental and computational results were expected to help to find a class of glycoside drugs whose target receptor was Dectin-1. CONCLUSION: Fractal dimension, differing from other known macro parameters, is a useful tool to characterize the compound molecules' microscopic structure and function, which may play an important role in the molecular design and biological activity study. In the process of oligosaccharides drug screening, the fractal dimension of receptor and designed oligosaccharides or glycoclusters can be calculated respectively. The oligosaccharides with fractal dimension close to that of target receptor should then take priority compared with others, to get the drug molecules with latent activity.

[Quantitative calculation of drugs distribution parameter in the brain extracellular space by using MRI tracer].

OBJECTIVE: To build a mathematical model to simulate the drug distribution accompanying with diffusion, distribution and clearance in the brain extracellular space (ECS). METHODS: Magnetic resonance imaging (MRI) technology was used to monitor changes in the signal-intensity-related tracer gadolinium-diethylene triamine pentaacetic acidm(Gd-DTPA), as an external drug which was injected into the rat brain, and then the mathematical model was built by using the data to establish the diffusion, distribution and clearance process of Gd-DTPA in the brain ECS. The model equation was resolved by Laplace transform. In the sphere coordinates, the linear regressive model was adopted to obtain the estimation method of diffusion coefficient, clearance rate of drugs distribution in the brain ECS. RESULTS: The diffusion coefficient D and the clearance rate k were obtained as (2.73±0.364)×10(-4) mm(2)/s and (1.40±0.206)×10(-5) /s, respectively. CONCLUSION: The proposed method can accurately reflect the isotropic drug distribution in the brain ECS, and can serve as the foundation to further solve problems about the orthotropic distribution in the brain ECS.

Knockdown of hTERT alters biophysical properties of K562 cells resulting in decreased migration rate in vitro.

It has been shown that 90% of tumors, including hematological malignant tumors and leukemia, have much higher levels of telomerase expression than normal cells. To investigate the effect of telomerase on leukemia cells, we transfected K562, a human erythroleukemia cell line with an antisense-hTERT (human telomerase reverse transcriptase) cDNA vector, and examined the biological and biophysical properties of the stably transfected cells (referred to as KAT). Un-transfected cells (K562) and cells transfected with the empty vector (referred to as KC) were used as controls. Cell growth curve and (3)H-TdR test showed that the growth rate and DNA synthesis of KAT decreased compared with those of K562 and KC cells. Apoptosis and cell cycle distribution in KAT cells under normal culture condition were similar to those of K562 and KC cells, but changed after serum deprivation. KAT cells had significantly different biophysical characteristics from K562 and KC in terms of cell electrophoresis, membrane fluidity, membrane fluidity, and viscoelasticity. Furthermore, the transendothelial migration rate of KAT was much lower than those of K562 and KC cells. Confocal microscopy showed that KAT cells had higher F-actin content, suggesting the reorganization of cytoskeleton. Flow cytometry analysis revealed a lowered intracellular calcium concentration and CD71 expression, explaining the high F-actin content in KAT cells. In conclusion, we found that the knockdown of hTERT in K562 cells changed their cytoskeleton and biophysical features, and reduced the cell migration.

Acute dichlorvos poisoning induces hemorheological abnormalities in rabbits via oxidative stress.

Dichlorvos is an important insecticide used largely. Some studies have demonstrated that organophosphate pesticide has effects on erythrocyte membrane structures, which is critical to erythrocyte function and hemorheology. The aim of the present study was to explore the effect of oxidative stress on hemorheological changes during dichlorvos poisoning in rabbits. Data indicated that after dichlorvos exposure the hematocrit adjusted viscosity at high shear rate increased and erythrocyte membrane fluidity decreased. Data obtained from plasma showed that lipid peroxidative substance-malonaldehyde was elevated and superoxide dismutase was reduced. In summary, oxidative stress does occur in dichlorvos poisoning and may lead to hemorheological alterations. The changes of hemorheology may be responsible for the pathophysiology of the dichlorvos poisoning.

Ryanodine receptor 1 mediates Ca2+ transport and influences the biomechanical properties in RBCs.

Ryanodine receptors (RyRs) are a family of Ca2+ channel proteins that mediate the massive release of Ca2+ from the endoplasmic reticulum into the cytoplasma. In the present study, we manipulated the incorporation of RyR1 into RBC membrane and investigated its influences on the intracellular Ca2+ ([Ca2+](in)) level and the biomechanical properties in RBCs. The incorporation of RyR1 into RBC membranes was demonstrated by both immunofluorescent staining and the change of [Ca2+](in) of RBCs. In the presence of RyR1, [Ca2+](in) showed biphasic changes, i.e., it increased with the extracellular Ca2+ ([Ca2+](ex)) up to 5muM and then decreased with the further increase of [Ca2+](ex). However, [Ca2+](in) remained constant in the absence of the RyR1. The results of biomechanical measurements on RBCs, including deformability, osmotic fragility, and membrane microviscosity, reflected similar biphasic changes of [Ca2+](in) mediated by RyR1 with the increases of [Ca2+](ex). Therefore, it is believed that RyR1 can incorporate into RBC membrane in vitro, and mediate Ca2+ influx, and then regulate RBC biomechanical properties. This information suggests that RBCs may serve as a model to study the function of RyR1 as a Ca2+ release channel.

The measurement of shear modulus and membrane surface viscosity of RBC membrane with Ektacytometry: a new technique.

A new technique is proposed to estimate the shear modulus (mu) and membrane surface viscosity (eta(m)) of red blood cell (RBC). Theoretical formulae for finding these two parameters are first derived based on the force balance on a RBC in a flow field of low viscosity. Different types of Ektacytometry are then used to measure relevant quantities. The obtained values (mu=6.1 x 10(-6)N/m, eta(m)=8.8 x10 (-7)Ns/m for normal RBC) are consistent with those previously found by micropipette technique and in AC electric field. The present technique is, however, much easier to operate and more advantageous in reflecting the average properties of a large quantity of RBCs, and it is much cheaper to be applied in clinical practice than any other method of measuring the two parameters. The sensitivity of the technique is demonstrated by testing RBCs treated with glutaraldehyde of different concentrations. This technique was demonstrated by the flow chamber.

Exogenous wild-type p53 gene improved survival of nude mice injected with murine erythroleukemia cell line through amelioration of hemorheological changes.

OBJECTIVES: Previous investigations have shown that human wild-type p53 gene (WTp53) inhibits the growth of leukemia and tumor cells in vitro. In the present study, the authors used nude mice and examined the therapeutic role of p53 gene for erythroleukemia in vivo in the absence of MHC effects. METHODS: The nude mice were injected with murine erythroleukemia cells (MEL), MEL cells transfected with wild-type p53 gene (MEL-W), and MEL cells transfected with mutated p53 gene (MEL-M). Abnormalities were found in the hemorheological and biophysical properties of red blood cells in all 3 groups of animals, but the abnormalities were lesser in degree and later in appearance in MEL-W group than in MEL and MEL-M groups. Furthermore, the nude mice in MEL-W group lived longer than those in MEL and MEL-M groups. RESULTS: The results showed that WTp53 restrained the growth of erythroleukemia cells in vivo and reduced the erythroleukemia tumorigenesis in the microcirculation by improving the hemorheological and biophysical properties of MEL cells, which helped to prolong the life span of nude mice suffering from erythroleukemia. CONCLUSION: These results contribute to our knowledge on the use of wild-type p53 gene for the treatment of erythroleukemia disease.

Effects of TFAR19 gene on the in vivo biorheological properties and pathogenicity of mouse erythroleukemia cell line MEL.

After injecting VP16, MEL cells and MEL-TF19 cells into the body of mice, with those injected with the same dose of saline as the control group, we observed the mice for their blood pictures, histological changes of the liver and spleen, and the hemorheological indexes within 4 weeks. The results indicated that after injecting MEL cells, the mice entered into a pathological status similar to erythroleukemia, which had the following exhibitions: the tissue structures of the liver and spleen were damaged, a mass of proerythroblasts, basophil erythroblasts and polychromatophilic erythroblasts could be observed on the smears of the bone marrow and spleen, and the deformability and orientation ability of erythrocytes were both depressed. The pathogenicity of MEL-TF19 cells carrying TFAR19 gene was obviously lower than that of MEL cells, and the MEL-TF19 cells even lost their faintish pathogenicity under the apoptosis-inducing effect of the chemotherapeutic reagent. The outcome from the animal experiments suggests that the TFAR19 gene suppresses the pathogenicity of MEL cells to the mice, and the effect may be better exerted with the synergy of the chemotherapeutic reagent.

TRAIL gene reorganizes the cytoskeleton and decreases the motility of human leukemic Jurkat cells.

TRAIL can selectively induce rapid apoptosis of various types of tumor cells. We induced the expression of TRAIL in Jurkat cells, and measured the adhesion of cells to human umbilical vein endothelial cells (HUVECs) and laminin (LN) in a parallel plate flow chamber system and by using a colorimetric method. The apoptosis percentage, cycle distribution, intracellular Ca(2+) concentration, and adhesion molecule expression of the cells were detected by flow cytometry. Cytoskeleton was observed with a laser confocal microscopy. The roles of adhesion molecules in the cell interaction was defined by their function blocking. The results showed that TRAIL attenuated the adhesion of Jurkat cells to HUVECs and LN, as well as their transendothelial migration. The increased apoptosis and G1-phase cell percentages, decreased intracellular Ca(2+) concentration, depolymerized actin and impaired cell deformability could contribute to the decreased adhesion of Jurkat cells caused by TRAIL. Furthermore, CD11a was found to play a more important role than CD62L in the adhesion of Jurkat cells to HUVECs. These findings contribute to the knowledge on the role of TRAIL in tumor metastasis and provide mechanistic basis for the clinical application of TRAIL and tumor therapy.