Investigation of common, low-frequency and rare genome-wide variation in anorexia nervosa

Anorexia nervosa (AN) is a complex neuropsychiatric disorder presenting with dangerously low body weight, and a deep and persistent fear of gaining weight. To date, only one genome-wide significant locus associated with AN has been identified. We performed an exome-chip based genome-wide association studies (GWAS) in 2158 cases from nine populations of European origin and 15 485 ancestrally matched controls. Unlike previous studies, this GWAS also probed association in low-frequency and rare variants. Sixteen independent variants were taken forward for in silico and de novo replication (11 common and 5 rare). No findings reached genome-wide significance. Two notable common variants were identified: rs10791286, an intronic variant in OPCML (P=9.89 × 10-6), and rs7700147, an intergenic variant (P=2.93 × 10-5). No low-frequency variant associations were identified at genome-wide significance, although the study was well-powered to detect low-frequency variants with large effect sizes, suggesting that there may be no AN loci in this genomic search space with large effect sizes.

Characterization of novel benzodiazepine ligands in Spodotera frugiperda (Sf-9) insect cells

The goals of the present work were to characterize the binding profile of nine benzodiazepine ligands in Spodotera frugiperda (Sf-9) insect cells expressing specific gamma aminobutyric acid (A) (GABA(A)) receptor subunit combinations and compare the affinities to those for the receptors in the rat cerebellum. Three recombinant baculovirus constructs, each harboring a different GABA(A) receptor subunit, were introduced into insect cells by simultaneous infection. Saturation and competition binding assays were carried out in membranes from Sf-9 cells infected with either alpha1beta2gamma2 or alpha6beta2gamma2 subunit combinations. The affinities of the ligands to the alpha1beta2gamma2 or alpha6beta2gamma2 receptors expressed in Sf-9 cells were similar to the affinities previously determined for the alpha1 or alpha6 subunit-containing GABA(A) receptors in the rat cerebellum, respectively, thus confirming the previously assigned receptor types in the cerebellum.

Aziridinyl nitropyrroles and nitropyrazoles as hypoxia-selective cytotoxins and radiosensitizers

A series of 1- and 2-substituted 4- and 5-nitropyrroles and 3- and 4-nitropyrazoles has been prepared and evaluated in vitro as radiosensitizers of hypoxic cells and as bioreductively-activated cytotoxins. Both the nitropyrroles and the nitropyrazoles were considerably less effective, based upon the differential between hypoxic and aerobic toxicity, than were similar 2-nitroimidazoles bearing alkylating moieties. The trends in radiosensitizing efficiency observed for both classes of drugs corresponded with their one-electron reduction potentials (E1(7] as measured by pulse radiolysis, although they were generally more effective than predicted from previous correlations of E1(7] with sensitizing efficacy and reactivities. Furthermore, the enhancement of sensitizing efficiency by the incorporation of alkylating groups is considerably greater than has been observed for nitroimidazoles. alpha-[(1-Aziridinyl)methyl]-3-nitropyrazole- 1-ethanol (10, E1(7) = -456 mV) and methyl 5-nitro-1-(cyclopropylcarbonyl)pyrrole-2-carboxylate (25, E1(7) = -326 mV) were the most effective radiosensitizers in vitro. Only 3-[cis-2,3-dimethyl-1-aziridinyl) methyl)-1-oxo-3,4-dihydro-6-nitro-1-H-pyrrolo [2,1-c] oxazine (22) and methyl 5-nitro-1-(cyclopropylcarbonyl)pyrrole-2-carboxylate (25) showed significant bioreductively-activated cytotoxicity, with differentials of 3.5. Although these differential toxicities were coupled with significantly lower aerobic toxicity compared with similar 2-nitroimidazoles, this series was not deemed effective enough to warrant further evaluation. The electron affinity and radiosensitization could be manipulated by chemical design but hypoxia-selectivity was not clearly related to these properties.

The effects of three bioreductive drugs (mitomycin C, RSU-1069 and SR4233) on cell lines selected for their sensitivity to mitomycin C or ionising radiation

We have investigated the cross-sensitivity of a number of cell lines to three different classes of bioreductive drugs under both aerobic and hypoxic conditions. The cell lines used were selected for their sensitivity to DNA-damaging agents and fall into two groups. One group, MMC cells derived from CHO-K1 cells (Robson et al., 1985), show a range of sensitivities to mitomycin C in air. The second group, irs cells were cloned from V79 Chinese hamster fibroblasts (Jones et al., 1987) and exhibit sensitivity to ionising radiation. The sensitivity of both groups of cells to mitomycin C (MMC), RSU-1069 and SR4233 was assessed under aerobic and hypoxic conditions. No difference in aerobic or hypoxic toxicity of MMC was observed for CHO-K1 or MMC sensitive cell lines (MMC-2 and MMC-3). However, the MMC-resistant cell line (MMCr) was 10 times more sensitive under hypoxic than aerobic conditions. This suggests that MMCr cells lack or are deficient in the enzymes responsible for activating MMC under aerobic conditions compared to other MMC cells. In contrast, differential toxicities of between 3 and 30 have been observed for all CHO cells treated with RSU-1069 and SR4233. Treatment of V79 and irs cells with RSU-1069 and SR4233 also resulted in selective toxicity towards hypoxic cells. Differential toxicities between 50 and 100 were observed for V79 cells. For both RSU-1069 and SR4233, the hypoxic toxicities were similar in V79 and irs cells but in air, the radiation sensitive cells were up to 10 times more sensitive than wild type cells.

Antibody labelling and flow cytometric analysis of metaphase chromosomes reveals two discrete structural forms

Metaphase chromosomes from cultured Chinese Hamster Ovary cells were labelled in suspension with a monoclonal antibody to histone 2B, counterstained with propidium iodide (PI) and analysed by flow cytometry. Contour plots of antibody binding (FITC fluorescence) against DNA content (PI fluorescence) revealed two discrete forms of each individual chromosome, showing high and low levels of antibody binding respectively. The two types of chromosome were easily distinguishable by immunofluorescence microscopy. The distribution of individual chromosomes between the two populations was related to chromosome size, with larger chromosomes predominating in the low-labelling population and vice versa. Variations in ionic strength, pH, divalent cation concentration or preparation procedure influenced the absolute level of antibody binding but did not eliminate the two populations. In contrast, preincubation with intercalating dyes, such as ethidium and propidium, inhibited antibody binding and generated a single, low-labelling population. Preliminary evidence suggests that in vivo changes in chromosome structure can affect the distribution of chromosomes between the two populations. Prolonged exposure of cells to Colcemid prior to chromosome isolation, a procedure known to increase chromosome condensation, resulted in a progressive shift into the low-labelling population. Our results suggest that chromosomes undergo a relatively rapid transition from the high-labelling to the low-labelling form during the prometaphase-metaphase stage of mitosis. The timing of this transition appears to be size dependent, with the larger chromosomes preceding the smaller. The transition may represent a change in chromosome condensation.