Primary infection of mice with high titer inoculum respiratory syncytial virus: characterization and response to antiviral therapy

Intranasal infection of BALB/c mice with respiratory syncytial virus (RSV)-A2 (0.5 x 10(8) - 2.0 x 10(8) plaque-forming units, PFU) produced disease characterized by weight loss (2-3 g) and mortality (60%-100%) with the mean day of death ranging from 6-7 d after infection. The extent of RSV disease was inoculum titer-dependent and required a replication competent virus. Lung titers of virus peaked at 0.5-1 x 10(6) PFU/g wet weight. Bronchoalveolar lavage fluid (BALF) levels of IL-1beta, TNF-alpha, INF-gamma IL-12, IL-6, MIP-1alpha, RANTES, and protein were elevated, whereas IL-2, IL-4, IL-5, IL-13, and IL-10 were unchanged. Histological assessment of lungs revealed marked inflammatory pathology characterized by bronchiolitis, vasculitis, and interstitial pneumonia. Whole-body plethysmography revealed significant disease-associated deficits of respiratory function. Therapy with ribavirin administered either by the intranasal, subcutaneous, or oral route significantly reduced disease in a dose-dependent manner. Delaying the initiation of therapy resulted in a loss of activity for ribavirin. Synagis administered either intramuscularly as a single dose in prophylaxis or intranasally in prophylaxis, followed by therapy, also significantly reduced disease in a dose-dependent manner. Infection of mice with a high titer inoculum of RSV-A2 resulted in severe and fatal pulmonary disease that was responsive to treatment. This model may be useful to characterize the in vivo activity of experimental therapies for RSV infection.     

Changes in survival characteristics of Diplostomum spathaceum cercariae emerged from cadmium-exposed Lymnaea stagnalis

The effect of exposing Lymnaea stagnalis (Gastropoda: Pulmonata), infected with Diplostomum spathaceum (Trematoda: Diplostomatidae), to 100 microg l(-1) cadmium for 7 days on survival characteristics (survival, tail loss, decaudized cercarial life-span) of emerged cercariae was investigated. Exposure of L. stagnalis to cadmium resulted in significantly increased D. spathaceum cercarial survival and an inhibited tail loss compared to controls. The normal parallel relationship which exists over time between decreasing cercarial survival and increasing tail loss in controls was changed in cercariae from cadmium-exposed hosts with an increased proportion of cercarial deaths occurring without tail loss. The decaudized cercarial life-span over the survival period of the cercarial population did not significantly change. However comparisons between individuals decaudized during the initial 24 h time period with those which were decaudized during the final period of cercarial survival showed a significantly altered life span which did not occur in the control population. As a potential indicator of penetration 'fitness' comparisons were also undertaken between control and exposed cercariae decaudized during the initial 24 h time period, which revealed that the decaudized cercarial life-span from the exposed hosts was significantly different from controls. This may have important implications for the ability of cercariae to migrate through the tissues of their target host. The importance and relevance of these results to parasite transmission are discussed.     

Toxicity of cadmium and zinc mixtures to the decaudized cercarial life span of Diplostomum spathaceum

The effects of cadmium and zinc mixtures at concentrations ranging from 0.1 to 10,000 microg l(-1) on the life-span of decaudized cercarial bodies (cercariae that have shed their tails) of Diplostomum spathaceum (Trematoda: Diplostomatidae) was investigated. Cercariae were exposed to metal mixtures of equal and unequal concentrations, and a low-dose pre-treatment followed by a high-dose exposure mixtures. Metal mixtures demonstrated variable effects on decaudized cercariae either by increasing or reducing their life-span compared to single metal exposures dependent on concentration and the type of mixed metal treatment. Prolonged exposure to equal metal mixtures at low concentrations (0.1-100 microg l(-1)) resulted in a reduction in the life-span of decaudized cercariae at 0.1 and 100 microg l(-1) in those individuals decaudized during the initial 24 h exposure period compared with those decaudized during the final 24 h period of cercarial survival, whilst in controls there was no significant life-span change between the two time periods. Decaudized cercariae which were exposed to low concentrations (0.1-100 microg l(-1)) of equal metal mixtures were also evaluated for their role as an indicator of larval 'fitness' for migrating through the tissues of their target fish host for those individuals decaudized during the initial 24 h exposure period, and demonstrated only a limited change in their life-span compared to control and single metal exposures. The importance of metal mixtures in parasite establishment in the fish host is discussed.     

Hyperpolarization of murine small caliber mesenteric arteries by activation of endothelial proteinase-activated receptor 2

Activation of endothelial proteinase-activated receptor 2 (PAR-2) relaxes vascular smooth muscle (VSM) and causes hypotension by nitric oxide (NO)-prostanoid-dependent and -independent mechanisms. We investigated whether endothelium-dependent hyperpolarization of VSM was the mechanism whereby resistance caliber arteries vasodilated independently of NO. VSM membrane potentials and isometric tension were measured concurrently to correlate the electrophysiological and mechanical changes in murine small caliber mesenteric arteries. In uncontracted arteries, the PAR-2 agonist, SLIGRL-NH2 (0.1 to 10 micromol/L), hyperpolarized the VSM membrane potential only in endothelium-intact arterial preparations. This response was unaltered by treatment of arteries with inhibitors of NO synthases (L-NAME), soluble guanylyl cyclase (ODQ), and cyclooxygenases (indomethacin). L-NAME, ODQ, and indomethacin also failed to inhibit SLIGRL-NH2-induced hyperpolarization and of cirazoline-contracted mesenteric arteries. However, in blood vessels that were depolarized and contracted with 30 mmol/L KCl, the effects of the SLIGRL-NH2 on membrane potential and tension were not observed. SLIGRL-NH2-induced hyperpolarization and relaxation was inhibited completely by the combination of apamin plus charybdotoxin, but only partially inhibited after treatment with the combination of barium plus ouabain, suggesting an important role for SKCa and IKCa channels and a lesser role for Kir channels and Na+/K+ ATPases in the hyperpolarization response. We concluded that activation of endothelial PAR-2 hyperpolarized the vascular smooth muscle (VSM) cells of small caliber arteries, without requiring the activation of NO synthases, cyclooxygenases, or soluble guanylyl cyclase. Indeed, this hyperpolarization may be a primary mechanism for PAR-2-induced hypotension in vivo.     

Influence of cadmium exposure on the incidence of first intermediate host encystment by Echinoparyphium recurvatum cercariae in Lymnaea peregra

The effect of cadmium exposure of the snail first intermediate host Lymnaea peregra on the incidence of encystment of Echinoparyphium recurvatum (Digenea: Echinostomatidae) cercariae without emergence from the snail was investigated. Exposure to 100 microg l(-1) Cd for 72 h caused a significant increase in the incidence of first host encystment when compared to controls. In addition, autometallographic staining of E. recurvatum daughter rediae and developing cercariae showed that there was metal accumulation within their body tissues. The significance of these findings to parasite transmission in metal-polluted environments is discussed.     

DHEAS improves learning and memory in aged SAMP8 mice but not in diabetic mice

Dehydroepiandrosterone sulfate (DHEAS) has been reported to improve memory in aged animals and suggested as a treatment for age-related dementias. The SAMP8 mouse, a model of Alzheimer's disease, has an age-related impairment in learning and memory and an increase in brain levels of amyloid precursor protein (APP) and amyloid beta protein (Abeta). Male SAMP8 mice also have a decrease in testosterone, to which DHEA is a precursor. Diabetes has been suggested as a model of aging and to be linked to Alzheimer's disease. Diabetics can have memory deficits and lower DHEAS levels. Here, we examined the effects of chronic oral DHEAS on acquisition and retention for T-maze footshock avoidance in 12 mo male SAMP8 mice and in CD-1 mice with streptozocin-induced diabetes. Learning and memory were improved in aged SAMP8 mice, but not in CD-1 mice with streptozocin-induced diabetes. These findings suggest that DHEAS is more effective in reversing the cognitive impairments associated with overexpression of Abeta than with diabetes.     

Tocopherol Transfer Protein Sensitizes Prostate Cancer Cells to Vitamin E

Prostate cancer is a major cause of mortality in men in developed countries. It has been reported that the naturally occurring antioxidant α-tocopherol (vitamin E) attenuates prostate cancer cell proliferation in cultured cells and mouse models. We hypothesized that overexpression of the tocopherol transfer protein (TTP), a vitamin E-binding protein that regulates tocopherol status, will sensitize prostate cancer cells to the anti-proliferative actions of the vitamin. To test this notion, we manipulated the expression levels of TTP in cultured prostate cells (LNCaP, PC3, DU145, and RWPE-1) using overexpression and knockdown approaches. Treatment of cells with tocopherol caused a time- and dose-dependent inhibition of cell proliferation. Overexpression of TTP dramatically sensitized the cells to the apoptotic effects of α-tocopherol, whereas reduction (“knockdown”) of TTP expression resulted in resistance to the vitamin. TTP levels also augmented the inhibitory effects of vitamin E on proliferation in semi-solid medium. The sensitizing effects of TTP were paralleled by changes in the intracellular accumulation of a fluorescent analog of vitamin E and by a reduction in intracellular levels of reactive oxygen species and were not observed when a naturally occurring, ligand binding-defective mutant of TTP was used. We conclude that TTP sensitizes prostate cancer cells to the anti-proliferative effects of vitamin E and that this activity stems from the ability of protein to increase the intracellular accumulation of the antioxidant. These observations support the notion that individual changes in the expression level or activity of TTP may determine the responsiveness of prostate cancer patients to intervention strategies that utilize vitamin E.