Oviposition and oogenesis in virgin fire ant females Solenopsis invicta are associated with a high level of dopamine in the brain

Abstract. In the fire ant Solenopsis invicta Buren, virgin females are capable of shedding their wings (dealation) and laying haploid eggs. However, dealation and reproduction are inhibited by a queen primer pheromone that depresses the release of Juvenile Hormone by the corpora allata. In an attempt to identify other neural signals that trigger the reproductive system, we measured the effect on brain biogenic amines of separation from the queen. Dopamine in the brain of virgin females increased from 552 ± 42 to 971 ± 65 fMol/brain when reproduction and dealation were stimulated by 15 days of separation. Octopamine and 5-hydroxytryptamine did not change significantly after the separation. Isolated virgin females fed with a tyrosine hydroxylase inhibitor 3-iodo- l -tyrosine mixed in sucrose for 15 days laid significantly fewer eggs and had fewer chorionated oocytes in their ovarioles than females fed with sucrose only. Restoring dopamine biosynthesis by adding l -dopa to the food also restored oogenesis and oviposition. Dealation was not affected by 3-iodo- l -tyrosine or l -dopa. The possible role of dopamine as the neural target of the queen pheromone regarding its potent allotoregulatory effect in other insects is discussed.     

Tuning of the outer hair cell motor by membrane cholesterol

Cholesterol affects diverse biological processes, in many cases by modulating the function of integral membrane proteins. We observed that alterations of cochlear cholesterol modulate hearing in mice. Mammalian hearing is powered by outer hair cell (OHC) electromotility, a membrane-based motor mechanism that resides in the OHC lateral wall. We show that membrane cholesterol decreases during maturation of OHCs. To study the effects of cholesterol on hearing at the molecular level, we altered cholesterol levels in the OHC wall, which contains the membrane protein prestin. We show a dynamic and reversible relationship between membrane cholesterol levels and voltage dependence of prestin-associated charge movement in both OHCs and prestin-transfected HEK 293 cells. Cholesterol levels also modulate the distribution of prestin within plasma membrane microdomains and affect prestin self-association in HEK 293 cells. These findings indicate that alterations in membrane cholesterol affect prestin function and functionally tune the outer hair cell.     

Oxidation-reduction potential and paraoxonase-arylesterase activity in trauma patients

The amount of oxidative stress in severely traumatized patients is usually based on various individual parameters such as total antioxidants and lipid peroxidation. Serial measurements of plasma oxidation-reduction potential (ORP) in severely traumatized patients as a simple mean of assessing overall oxidative stress is described. Serial whole blood samples were obtained from multi-trauma patients (N=39) and healthy individuals (N=10). Plasma ORP in multi-trauma patients increased during the first few days of hospitalization and approached normal ORP levels upon discharge. On the ORP maxima day (5.8 days+/-0.5 SEM), a statistically significant decrease (p<0.05) was observed for negative acute phase reactants such as plasma paraoxonase-arylesterase (PON-AE) activity and total plasma protein in comparison with admission plasma levels. Monitoring ORP could be a useful tool for assessing the degree of oxidative stress, inflammation, severity of injury, and potential efficacy of treatment.     

Synthesis and crystal structure of tetrameric silver(I) 3,5-di-tert-butyl-pyrazolate

A tetrameric [Ag(μ-3,5-^tBu₂pz)]₄ · CH₂Cl₂ (1 · CH₂Cl₂) has been prepared and structurally characterized. The four Ag-atoms are in an approximate rhombic arrangement with pyrazolato bridges alternating on either side of the Ag₄-plane. A ¹H NMR study shows partial decomposition of 1 to the mononuclear [Ag(3,5-^tBu₂pzH)₂]⁺ in solution.     

Severe retinitis pigmentosa mapped to 4p15 and associated with a novel mutation in the PROM1 gene

Mutation in the PROM1 gene previously has been identified in one family with retinal degeneration for which neither ERG recordings nor detailed information about visual impairment is available. A large family with multiple individuals affected by retinal degeneration was ascertained in the Punjab province of Pakistan. The visual acuity of all affected patients in the family was severely compromised beginning in early childhood. The retinal disease in this family is a severe form of retinitis pigmentosa (RP) accompanied by macular degeneration. Fundus changes advanced with age. Choriocapillaris atrophy and posterior RPE atrophy were obvious allowing visualization of the large choroidal vessels in patients over 40 years of age. Rod and cone responses on ERG recordings were extinguished in patient’s teens. A genome-wide scan mapped the disease to a 34.7 cM region of chromosome 4p14–p16 between D4S1599 and D4S405. A maximum lod score of 3.96 with D4S403 and D4S391 is seen at θ = 0. Sequence analysis of PROM1 located in the linkage interval identified a c.1726C>T homozygous transition in exon 15: resulting in p.Gln576X in the translated protein. This mutation is found in a homozygous state in all six affected individuals and was heterozygous in five of the six unaffected family members examined. The mutation was not detected in 192 chromosomes of unrelated control individuals of the same ethnicity and from the same region. This delineates the phenotypic characteristics of retinopathy caused by mutations in PROM1. Qingjiong Zhang, Fareeha Zulfiqar, Xueshan Xiao, Sheikh Riazuddin and J. Fielding Hejtmancik contributed equally.     

Synthesis, biological evaluation and molecular modelling of sulfonohydrazides as selective PI3K p110alpha inhibitors

A series of 2-methyl-5-nitrobenzenesulfonohydrazides were prepared and evaluated as inhibitors of PI3K. An isoquinoline derivative shows good selectivity for the p110α isoform over p110β and p110δ, and also demonstrates good in vitro activity in a cell proliferation assay. Molecular modelling provides a rationalisation for the observed SAR.     

Computational model of vectorial potassium transport by cochlear marginal cells and vestibular dark cells

Cochlear marginal cells and vestibular dark cells transport potassium into the inner ear endolymph, a potassium-rich fluid, the homeostasis of which is essential for hearing and balance. We have formulated an integrated mathematical model of ion transport across these epithelia that incorporates the biophysical properties of the major ion transporters and channels located in the apical and basolateral membranes of the constituent cells. The model is constructed for both open- and short-circuit situations to test the extremes of functional capacity of the epithelium and predicts the steady-state voltages, ion concentrations, and transepithelial currents as a function of various transporter and channel densities. We validate the model by establishing that the cells are capable of vectorial ion transport consistent with several experimental measurements. The model indicates that cochlear marginal cells do not make a significant direct contribution to the endocochlear potential and illustrates how changes to the activity of specific transport proteins lead to reduced K⁺ flux across the marginal and dark cell layers. In particular, we investigate the mechanisms of loop diuretic ototoxicity and diseases with hearing loss in which K⁺ and Cl^– transport are compromised, such as Jervell and Lange-Nielsen syndrome and Bartter syndrome, type IV, respectively. Such simulations demonstrate the utility of compartmental modeling in investigating the role of ion homeostasis in inner ear physiology and pathology. stria vascularis; endolymph; endocochlear potential; biological modeling     

Induced parthenogenesis in mandarin for haploid production: induction procedures and genetic analysis of plantlets

This study focused on haploid induction in mandarin through in situ gynogenesis by pollination with irradiated pollen of ‘Meyer’ lemon. Pollination was carried out for three genotypes of mandarin with four levels of gamma-ray-irradiated pollen (150, 300, 600, and 900 Gy). The resulting seeds were characterised by a small size. Embryos were rescued in vitro and the ploidy level of the plantlets was determined by flow cytometry analysis. Haploid, diploid, triploid plantlets were obtained. The haploid parthenogenetic origin was confirmed using microsatellite marker analysis and chromosome count. Diploid and triploid plants were the result of crosses between mandarin and lemon. The induction of gynogenetic haploids of ‘Fortune’ (Citrus clementina Hort ex Tan. × Citrus tangerina Hort ex Tan.) and ‘Ellendale’ (Citrus reticulata Blanco × Citrus sinensis L. Osb) is reported here for the first time.