Highly purified lipoteichoic acid from gram-positive bacteria induces in vitro blood-brain barrier disruption through glia activation: role of pro-inflammatory cytokines and nitric oxide.

The co-culture of bovine brain capillary endothelial cells and rat primary glial cells was established as an in vitro blood-brain barrier model to investigate the mechanisms by which the Gram-positive bacterial cell wall components lipoteichoic acid and muramyl dipeptide induced injury of blood-brain barrier structure and function. We found that highly purified lipoteichoic acid disrupted blood-brain barrier integrity in a concentration- and time-dependent manner indirectly, through glia activation. Low trans-endothelial electrical resistance and high permeability to fluorescein isothiocyanate-inulin observed in the presence of lipoteichoic acid-activated glial cells were potentiated by muramyl dipeptide and could be reversed only when glial cells were activated by lipoteichoic acid at 10 microg/ml but not with a higher lipoteichoic acid concentration (30 microg/ml). Immunocytochemistry analysis revealed no evident changes in the distribution of the cytoskeleton protein F-actin and tight junction proteins occludin and claudin after lipoteichoic acid treatment. However, the tight junction associated protein AHNAK clearly revealed the morphological alteration of the endothelial cells induced by lipoteichoic acid. Lipoteichoic acid-activated glial cells produced nitric oxide and pro-inflammatory cytokines (tumor necrosis factor-alpha and interleukin-1beta) that contributed to lipoteichoic acid-induced blood-brain barrier disruption, since the direct treatment of the endothelial monolayer with tumor necrosis factor-alpha or interleukin-1beta increased blood-brain barrier permeability, whereas the pre-treatment of lipoteichoic acid-activated glial cells with antibodies against these two cytokines blocked lipoteichoic acid effects. Additionally, nitric oxide was also involved in blood-brain barrier damage, since the nitric oxide donor itself (diethylenetriamine-nitric oxide adduct) increased blood-brain barrier permeability and inducible nitric oxide synthase inhibitor (1400W) partially reversed lipoteichoic acid-induced trans-endothelial electrical resistance decrease.

Effects of gamma- and hydroxypropyl-gamma-cyclodextrins on the transport of doxorubicin across an in vitro model of blood-brain barrier.

Association between doxorubicin (DOX) and gamma-cyclodextrin (gamma-CD) or hydroxypropyl-gamma-CD (HP-gamma-CD) has been examined to increase the delivery of this antitumoral agent to the brain. The stoichiometry and the stability constant of gamma-CD or HP-gamma-CD and DOX complexes were determined in physiological medium by UV-visible spectroscopy. By using an in vitro model of the blood-brain barrier (BBB), endothelial permeability and toxicity toward the brain capillary endothelial cells of DOX, gamma-CD, and HP-gamma-CD were performed. For each CD, endothelial permeability was relatively low and a disruption of the BBB occurred at 20 microM, 20 mM, and 50 mM DOX, gamma-CD, and HP-gamma-CD, respectively. Increasing amounts of CDs were added to a fixed DOX concentration. Addition of gamma-CD or HP-gamma-CD, up to 15 and 35 mM, respectively, decreased the DOX delivery, probably due to the low complex penetration across the BBB and the decrease in free DOX concentration. Higher CD concentrations increased the DOX delivery to the brain, but this effect is due to a loss of BBB integrity. In contrast to what was observed on Caco-2 cell model with various drugs, CDs are not able to increase the delivery of DOX across our in vitro model of BBB.

Effect of spaceflight on single fiber function of triceps and biceps muscles in rhesus monkeys.

Primates appeared to be a good model for investigating muscle contractile and biochemical properties, as well as EMG recordings. The purpose of our study was to examine the effects of microgravity on the contractile properties of the slow-type triceps and fast-type biceps muscles during the 14-day Bion 11 spaceflight.

[Testing the fertility of the spermatozoa]. / Test de fécondance des spermatozoïdes.

The sperm count, an absolutely necessary examination, seems no longer sufficient to establish a prognosis of fertility. Fertilization in vitro, for a diagnostic purpose, would be the ideal examination, but because of the ethical and technical problems it raises, other tests have been developed. The test of spermatozoid survival at 24 hours in Menezzo's B2 medium and interspecific fertilization in vitro (hamster-test) are carried out on isolated spermatozoids according the FIV protocol. The survival test provides two parameters: the presence of mobility and the rate of retention of the mobility after 24 hours. With the hamster-test it is possible to study the penetration and decondensation of the spermatozoids in the ovocytes. The results obtained with the survival test show that the absence of gradual mobility and a retention rate below 25 p. cent after 24 hours, significantly affect the cleavage of ovocytes during FIV. These two parameters affect, in a similar fashion, the percentage of fertilized ovocytes in the hamster-test. The latter seems less specific than the survival test to establish a prognosis before FIV. However, it is interesting as it allows the study of the different stages of fertilization of spermatozoid samples, from the same ejaculation, under varied experimental conditions. These tests require a standardization and present a definite advantage during exploration prior to FIV, AIC.