Phytochelatin synthesis is not responsible for Cd tolerance in the Zn/Cd hyperaccumulator Thlaspi caerulescens (J. & C. Presl)

Thlaspi caerulescens (J. & C. Presl, "Prayon") is a heavy-metal hyperaccumulator that accumulates Zn and Cd to high concentrations (40,000 and 4,000 mg kg DW-1 respectively) without phytotoxicity. The mechanism of Cd tolerance has not been characterized but reportedly involves vacuolar sequestration. The role of phytochelatins (PCs) in metal tolerance in T. caerulescens and the related non-accumulator T. arvense was examined. Although PCs were produced by both species in response to Cd, these peptides do not appear to be involved in metal tolerance in the hyperaccumulator. Leaf and root PC levels for both species showed a similar positive correlation with tissue Cd, but total PC levels in the hyperaccumulator were generally lower, despite correspondingly higher metal concentrations. The lack of a role for PCs in the hyperaccumulator's response to metal stress suggests that other mechanisms are responsible Cd tolerance. The lower level of leaf PCs in T. caerulescens also implies that Cd in the shoot is sequestered in a compartment or form that does not elicit a PC response.     

Decrease of core body temperature in mice by dehydroepiandrosterone

Dietary dehydroepiandrosterone (DHEA) reduces food intake in mice, and this response is under genetic control. Moreover, both food restriction and DHEA can prevent or ameliorate certain diseases and mediate other biological effects. Mice fed DHEA (0.45% w/w of food) and mice pair-fed to these mice (food restricted) for 8 weeks were tested for changes in body temperature. DHEA was more efficient than food restriction alone in causing hypothermia. DHEA injected intraperitoneally also induced hypothermia that reached a nadir at 1 to 2 hr, and slowly recovered by 20 to 24 hr. This effect was dose dependent (0.5-50 mg). Each mouse strain tested (four) was susceptible to this effect, suggesting that the genetics differ for induction of hypophagia and induction of hypothermia. Because serotonin and dopamine can regulate (decrease) body temperature, we treated mice with haloperidol (dopamine receptor antagonist), 5,7-dihydroxytryptamine (serotonin production inhibitor), or ritanserin (serotonin receptor antagonist) prior to injection of DHEA. All of these agents increased rather than decreased the hypothermic effects of DHEA. DHEA metabolites that are proximate (5-androstene-3beta, 17beta-diol and androstenedione) or further downstream (estradiol-17beta) were much less effective than DHEA in inducing hypothermia. However, the DHEA analog, 16alpha-chloroepiandrosterone, was as active as DHEA. Thus, DHEA administered parentally seems to act directly on temperature-regulating sites in the body. These results suggest that DHEA induces hypothermia independent of its ability to cause food restriction, to affect serotonin or dopamine functions, or to act via its downstream steroid metabolites.     

Determination of olanzapine in plasma by high-performance liquid chromatography using ultraviolet absorbance detection

A rapid method for the determination of olanzapine in plasma using high-performance liquid chromatography with ultra violet detection is described. Olanzapine was extracted from plasma with a mixture of hexane/dichloromethane (85:15), and then back extracted into phosphate buffer pH 2.8. Separation was achieved on a RP Select B C(18) column and commonly administered drugs did not interfere with the assay. The limit of quantitation was 1.5 microg/l and the inter-day and intra-day relative standard deviations were less than 10%. Olanzapine was shown to be stable in plasma for up to 7 days when stored at 4 degrees C. Moreover, the addition of ascorbic acid was not necessary for the achievement of chemical stability during storage, or during the assay procedure. The method has been used to measure olanzapine concentrations in patients treated with various doses of the drug varying from 5 to 40 mg/day.     

The alpha 2-adrenergic receptor gene and body fat content and distribution: the HERITAGE Family Study

BACKGROUND: Among adrenergic receptor subtypes that regulate lipid mobilization, the alpha2-adrenergic receptor is involved in the inhibition of fatty acid mobilization from adipose tissue. A C-1291G polymorphism is located in the alpha2-adrenergic receptor gene (ADRA2A) but no association with body fat accumulation has been reported yet. MATERIALS AND METHODS: Body mass index (BMI), fat mass (FAT), percentage body fat (%FAT), trunk-to-extremity skinfold ratio (TER), sum of eight skinfolds (SF8), and abdominal subcutaneous (ASF), visceral (AVF), and total (ATF) fat areas assessed by CT scan have been measured in adult sedentary white (n = 503) and black (n = 276) subjects participating in the HERITAGE Family Study. Association between the C-1291G polymorphism and each phenotype was tested separately in men and women of each race using ANCOVA with the effects of age as covariate in addition to the effects of BMI for TER and of FAT for AVF, ASF, and ATF. RESULTS: The allele frequencies of the ADRA2A C-1291G polymorphism differed between races. No association was observed in white subjects, except for a moderate effect of the polymorphism accounting for less than 1% of the variance in AVF and ATF in women. In black subjects, however, the G-1291 allele was found to be associated with an increase of TER in men (3.8% of variance accounted for by the polymorphism), while in black women it was associated with a decrease in TER (2.9%) and in AVF (2.5%). CONCLUSION: These results suggest a role for the ADRA2A gene in determining the propensity to store fat in the abdominal area, independently of total body fatness.     

Toward positional cloning of Vgt1, a QTL controlling the transition from the vegetative to the reproductive phase in maize

Vgt1 (Vegetative to generative transition 1) is a quantitative trait locus (QTL) for flowering time in maize (Zea mays L.). Vgt1 was initially mapped in a ca. 5-cM interval on chromosome bin 8.05, using a set of near-isogenic lines (NILs) in the genetic background of the late dent line N28, with the earliness allele introgressed from the early variety Gaspé Flint. A new large mapping population was produced by crossing N28 and one early NIL with a ca. 6-cM long Gaspé Flint introgression at the Vgt1 region. Using PCR-based assays at markers flanking Vgt1, 69 segmental NILs homozygous for independent crossovers near the QTL were developed. When the NILs were tested in replicated field trials for days to pollen shed (DPS) and plant node number (ND), the QTL followed a Mendelian segregation. Using bulk segregant analysis and AFLP profiling, 17 AFLP markers linked to the QTL region were identified. Statistical analysis indicated a substantial coincidence of the effects of Vgt1 on both DPS and ND. Vgt1 was mapped at ca. 0.3 cM from an AFLP marker. As compared to DPS, the higher heritability of ND allowed for a more accurate assessment of the effects of Vgt1. The feasibility of the positional cloning of Vgt1 is discussed.     

Photoperiodic Control of Developmental Diapause in Nymphs of Prostriate Ixodid Ticks (Acari: Ixodidae)

Extrinsic control of developmental diapause in nymphs of prostriate ticks of the subgenus Ixodes sensu stricto (Ixodes ricinus and Ixodes persulcatus from Eurasia and Ixodes scapularis from North America) appears to be based on a complex two-step photoperiodic reaction of a short-day/long-day type. Diapause control in the subgenus Afrixodes (the South African tick Ixodes rubicundus) appears to be based on a simple long-day reaction. The option between non-diapause development and diapausing arrest in engorged nymphs is determined by both pre- and post-feeding photoperiodic regimes. Consequently diapausing arrest in engorged nymphs of Ixodes sensu stricto can be induced either by a short-day (after their engorgement) or by a long-day regime (in unfed nymphs), while active, non-diapause development is possible only when the short-day pre-feeding regime is followed by a long-day post-feeding regime. The photoperiodic response in I. (Afrixodes) rubicundus nymphs seems to be of the long-day type both before and after feeding. Consequently this non-diapause development is enabled by a long-day regime, while diapause is induced by a short-day regime of exposure. Nevertheless, there are some indications that the control of nymphal diapause in the latter species is also of a complex nature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Magnetic field design for selecting and aligning immunomagnetic labeled cells

BACKGROUND: Recently we introduced the CellTracks cell analysis system, in which samples are prepared based on a combination of immunomagnetic selection, separation, and alignment of cells along ferromagnetic lines. Here we describe the underlying magnetic principles and considerations made in the magnetic field design to achieve the best possible cell selection and alignment of magnetically labeled cells. Materials and Methods Computer simulations, in combination with experimental data, were used to optimize the design of the magnets and Ni lines to obtain the optimal magnetic configuration. RESULTS: A homogeneous cell distribution on the upper surface of the sample chamber was obtained with a magnet where the pole faces were tilted towards each other. The spatial distribution of magnetically aligned objects in between the Ni lines was dependent on the ratio of the diameter of the aligned object and the line spacing, which was tested with magnetically and fluorescently labeled 6 microm polystyrene beads. The best result was obtained when the line spacing was equal to or smaller than the diameter of the aligned object. CONCLUSIONS: The magnetic gradient of the designed permanent magnet extracts magnetically labeled cells from any cell suspension to a desired plane, providing a homogeneous cell distribution. In addition, it magnetizes ferro-magnetic Ni lines in this plane whose additional local gradient adds to the gradient of the permanent magnet. The resultant gradient aligns the magnetically labeled cells first brought to this plane. This combination makes it possible, in a single step, to extract and align cells on a surface from any cell suspension.     

Cell analysis system based on compact disk technology

BACKGROUND: A cell analysis system was developed to enumerate and differentiate magnetically aligned cells selected from whole blood. The cellular information extracted is similar to the readout of musical information from a compact disk (CD). Here we describe the optical design and data processing of the system. The performance of the system is demonstrated using fluorescent-labeled cells and beads. Materials and Methods System performance was demonstrated with 6-microm polystyrene beads labeled with magnetic nanoparticles and allophycocyanin (APC) and immunomagnetically aligned leukocytes, fluorescently labeled with Oxazine750 and CD4-APC, CD8-Cy5.5, and CD14-APC/Cy7 in whole blood. RESULTS: The sensitivity of the system was demonstrated using APC-labeled beads. With this system, beads containing 333 APC molecules could easily be resolved from the background. This level of sensitivity was not achievable with a commercial flow cytometer. A maximum of 20,000 immunomagnetically labeled cells could be aligned and analyzed in between 0.6 m of Ni lines, distributed over a surface area of 18 mm(2) and extracted from a blood volume that depended on the height of the chamber. The utility of the system was demonstrated by performing a three-color CD4-CD8-CD14 assay. CONCLUSIONS: We built a cell analysis system based on immunomagnetic cell selection and alignment and analysis of fluorescent signals employing CD-technology that is as good or better than current commercial analyzers. The cell analysis can be performed in whole blood or any other type of cell suspension without extensive sample preparation.     

Cholesterol,oxidative stress,and Alzheimer's disease: expanding the horizons of pathogenesis

Recent epidemiological, clinical, and experimental data suggest that cholesterol may play a role in Alzheimer's disease (AD). We have recently shown that cholesterolemia has a profound effect in the development and modulation of amyloid pathology in a transgenic model of AD. This review summarizes recent advancements in our understanding of the potential role of cholesterol and the amyloid beta protein in initiating the generation of free radicals and points out their role in a chain of events that causes damage of essential macromolecules in the central nervous system and culminates in neuronal dysfunction and loss. Experimental data links cholesterol and oxidative stress with some neurodegenerative aspects of AD.