Cryptochrome Mediates Light-Dependent Magnetosensitivity of Drosophila's Circadian Clock

Since 1960, magnetic fields have been discussed as Zeitgebers for circadian clocks, but the mechanism by which clocks perceive and process magnetic information has remained unknown. Recently, the radical-pair model involving light-activated photoreceptors as magnetic field sensors has gained considerable support, and the blue-light photoreceptor cryptochrome (CRY) has been proposed as a suitable molecule to mediate such magnetosensitivity. Since CRY is expressed in the circadian clock neurons and acts as a critical photoreceptor of Drosophila's clock, we aimed to test the role of CRY in magnetosensitivity of the circadian clock. In response to light, CRY causes slowing of the clock, ultimately leading to arrhythmic behavior. We expected that in the presence of applied magnetic fields, the impact of CRY on clock rhythmicity should be altered. Furthermore, according to the radical-pair hypothesis this response should be dependent on wavelength and on the field strength applied. We tested the effect of applied static magnetic fields on the circadian clock and found that flies exposed to these fields indeed showed enhanced slowing of clock rhythms. This effect was maximal at 300 μT, and reduced at both higher and lower field strengths. Clock response to magnetic fields was present in blue light, but absent under red-light illumination, which does not activate CRY. Furthermore, cry^b and cry^OUT mutants did not show any response, and flies overexpressing CRY in the clock neurons exhibited an enhanced response to the field. We conclude that Drosophila's circadian clock is sensitive to magnetic fields and that this sensitivity depends on light activation of CRY and on the applied field strength, consistent with the radical pair mechanism. CRY is widespread throughout biological systems and has been suggested as receptor for magnetic compass orientation in migratory birds. The present data establish the circadian clock of Drosophila as a model system for CRY-dependent magnetic sensitivity. Furthermore, given that CRY occurs in multiple tissues of Drosophila, including those potentially implicated in fly orientation, future studies may yield insights that could be applicable to the magnetic compass of migratory birds and even to potential magnetic field effects in humans.     

Fixed-bed adsorption performance of oil palm shell-based activated carbon for removal of 2,4,6-trichlorophenol

This study investigated the adsorption potential of oil palm shell-based activated carbon to remove 2,4,6-trichlorophenol from aqueous solution using fixed-bed adsorption column. The effects of 2,4,6-trichlorophenol inlet concentration, feed flow rate and activated carbon bed height on the breakthrough characteristics of the adsorption system were determined. The regeneration efficiency of the oil palm shell-based activated carbon was evaluated using ethanol desorption technique. Through ethanol desorption, 96.25% of the adsorption sites could be recovered from the regenerated activated carbon.     

Inactivation of uPA and its receptor uPAR by 3,3′‐diindolylmethane (DIM) leads to the inhibition of prostate cancer cell growth and migration

3,3′‐Diindolylmethane (DIM) has been studied for its putative anti‐cancer properties, especially against prostate cancer; however, its exact mechanism of action remains unclear. We recently provided preliminary data suggesting down‐regulation of uPA during B‐DIM (a clinically active DIM)‐induced inhibition of invasion and angiogenesis in prostate cancer cells. Since the expression and activation of uPA plays important role in tumorigenicity, and high endogenous levels of uPA and uPAR are found in advanced metastatic cancers, we investigated their role in B‐DIM‐mediated inhibition of prostate cancer cell growth and motility. Using PC3 cells, we found that B‐DIM treatment as well as the silencing of uPA and uPAR by siRNAs led to the inhibition of cell growth and motility. Conversely, over‐expression of uPA/uPAR in LNCaP and C4‐2B cells resulted in increased cell growth and motility, which was effectively inhibited by B‐DIM. Moreover, we found that uPA as well as uPAR induced the production of VEGF and MMP‐9, and that the down‐regulation of uPA/uPAR by siRNAs or B‐DIM treatment resulted in the inhibition of VEGF and MMP‐9 secretion which could be responsible for the observed inhibition of cell migration. Interestingly, silencing of uPA/uPAR led to decreased sensitivity to B‐DIM indicating important role of uPA/uPAR in B‐DIM‐mediated regulation of prostate cancer cell growth and migration. Our data suggest that chemopreventive and/or therapeutic activity of B‐DIM is in part due to down‐regulation of uPA–uPAR leading to reduced production of VEGF/MMP‐9 which ultimately leads to the inhibition of cell growth and migration of aggressive prostate cancer cells. J. Cell. Biochem. 107: 516–527, 2009. © 2009 Wiley‐Liss, Inc.     

Involvement of polyamines, abscisic acid and anti-oxidative enzymes in adaptation of Blue Panicgrass (Panicum antidotale Retz.) to saline environments

A hydroponic experiment was conducted to assess the possible involvement of polyamines (PAs), abscisic acid (ABA) and anti-oxidative enzymes such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in adaptation of six populations of Panicum antidotale Retz. to selection pressure (soil salinity) of a wide range of habitats. Plants of six populations were collected from six different habitats with ECe ranging from 3.39 to 19.23 dS m⁻¹ and pH from 7.65 to 5.86. Young tillers from 6-month-old plants were transplanted in plastic containers each containing 10 l of half strength Hoagland's nutrient solution alone or with 150 mol m⁻³ NaCl. After 42 days growth, contents of polyamines (Put, Spd and Spm) and ABA, and the activities of anti-oxidative enzymes (SOD, POD and CAT) of all populations generally increased under salt stress. The populations collected from highly saline habitats showed a greater accumulation of polyamines and ABA and the activities of anti-oxidative enzymes as compared to those from mild or non-saline habitats. Moreover, Spm/Spd and Put/(Spd + Spm) ratios generally increased under salt stress. However, the populations from highly saline environments had significantly higher Spm/Spd and Put/(Spd + Spm) ratios as compared to those from mild or non-saline environments. Similarly, the populations adapted to high salinity accumulated less Na⁺ and Cl⁻ in culm and leaves, and showed less decrease in leaf K⁺ and Ca²⁺ under salinity stress. Higher activities of anti-oxidative enzymes and accumulation of polyamines and ABA, and increased Spm/Spd and Put/(Spm + Spd) ratios were found to be highly correlated with the degree of adaptability of Panicum to saline environment.     

Maintaining blood–brain barrier integrity: Pericytes perform better than astrocytes during prolonged oxygen deprivation

The blood–brain barrier (BBB), consisting of specialized endothelial cells surrounded by astrocytes and pericytes, plays a crucial role in brain homeostasis. Many cerebrovascular diseases are associated with BBB breakdown and oxygen (O₂) deprivation constitutes a critical factor that onsets its disruption. We investigated the impact of astrocytes and pericytes on brain endothelial cell permeability and survival during different degrees of O₂ deprivation. Prolonged exposure to 1% O₂ caused barrier breakdown and exposure to 0.1% O₂ dramatically accelerated disruption and induced cell death, mediated at least in part via caspase‐3 activation. Reoxygenation allowed only cells exposed to 1% O₂ to re‐establish barrier function. Notably co‐culture with astrocytes and pericytes substantially enhanced barrier function under normoxic conditions, and produced differential responses during O₂ deprivation. At 1% O₂ astrocytes partially maintained barrier integrity whereas pericytes accelerated its disruption in the short‐term, having positive effects only after prolonged exposure. Unexpectedly, at 0.1% O₂ pericytes were more effective than astrocytes in preserving barrier function although the protection afforded by both cells involved inhibition of caspase‐3 pathways. Furthermore, cell‐specific regulation of auto‐ and paracrine VEGF signaling pathways were also in part responsible for the differential modulation of barrier function. Our data suggests that cellular cross‐talk within the neurovascular unit is crucial for preservation of barrier integrity and that pericytes, not astrocytes, play a significant role during severe and prolonged O₂ deprivation. J. Cell. Physiol. 218: 612–622, 2009. © 2008 Wiley‐Liss, Inc.     

Extended access to cocaine self-administration results in reduced glutamate function within the medial prefrontal cortex

Previous studies have shown that brief access to cocaine yields an increase in D2 receptor binding in the medial prefrontal cortex (mPFC), but that extended access to cocaine results in normalized binding of D2 receptors (i.e. the D2 binding returned to control levels). Extended-access conditions have also been shown to produce increased expression of the NR2 subunit of the N-Methyl-D-aspartate receptor in the mPFC. These results implicate disrupted glutamate and dopamine function within this area. Therefore, in the present study, we monitored glutamate and dopamine content within the mPFC during, or 24 hours after, cocaine self-administration in animals that experienced various amounts of exposure to the drug. Na?ve subjects showed decreased glutamate and increased dopamine levels within the mPFC during cocaine self-administration. Exposure to seven 1-hour daily cocaine self-administration sessions did not alter the response to self-administered cocaine, but resulted in decreased basal dopamine levels. While exposure to 17 1-hour sessions also resulted in reduced basal dopamine levels, these animals showed increased dopaminergic, but completely diminished glutamatergic, response to self-administered cocaine. Finally, exposure to 17 cocaine self-administration sessions, the last 10 of which being 6-hour sessions, resulted in diminished glutamatergic response to self-administered cocaine and reduced basal glutamate levels within the mPFC while normalizing (i.e. causing a return to control levels) both the dopaminergic response to self-administered cocaine as well as basal dopamine levels within this area. These data demonstrate directly that the transition to escalated cocaine use involves progressive changes in dopamine and glutamate function within the mPFC.     

Purification and characterization of a new glucoamylopullulanase from thermotolerant alkaliphilic Bacillus subtilis DR8806 of a hot mineral spring

We have introduced a novel glucoamylopullulanase from thermostable alkaliphilic Bacillus subtilis DR8806 from a hot mineral spring in Iran. The enzyme was purified by ion-exchange chromatography following to ammonium sulphate precipitation. The molecular weight of the purified enzyme was estimated to be 65.5 kDa using denaturing acrylamide gel electrophoresis. The enzyme showed high activity over a wide pH range, from pH 5.0 to pH 11.0 with the optimum pH 9.5. Our results also indicated an optimum temperature of the enzyme activity at 70 °C. These features justify the characteristics of the alkaliphilic and thermostable bacterial proteins and enzymes. The enzyme did not require calcium and showed extreme stability with regard to surfactants, including SDS and Triton X-100, and oxidizing agents such as H₂O_2. These features of the enzyme suggest a promising potential for application in laundry industry. Furthermore, the enzyme was active on pulullan by 68% relative to normal activity on starch. Such characteristics have not already been reported for this type of enzyme, hence we propose that this is a new alkalophilic and thermostable enzyme.