Distribution of MT1 Melatonin Receptor Promoter-Driven RFP Expression in the Brains of BAC C3H/HeN Transgenic Mice

The pineal hormone melatonin activates two G-protein coupled receptors (MT₁ and MT₂) to regulate in part biological functions. The MT₁ and MT₂ melatonin receptors are heterogeneously distributed in the mammalian brain including humans. In the mouse, only a few reports have assessed the expression of the MT₁ melatonin receptor expression using 2-iodomelatonin binding, in situ hybridization and/or polymerase chain reaction (PCR). Here, we described a transgenic mouse in which red fluorescence protein (RFP) is expressed under the control of the endogenous MT₁ promoter, by inserting RFP cDNA at the start codon of MTNR1a gene within a bacterial artificial chromosome (BAC) and expressing this construct as a transgene. The expression of RFP in the brain of this mouse was examined either directly under a fluorescent microscope or immunohistochemically using an antibody against RFP (RFP-MT₁). RFP-MT₁ expression was observed in many brain regions including the subcommissural organ, parts of the ependyma lining the lateral and third ventricles, the aqueduct, the hippocampus, the cerebellum, the pars tuberalis, the habenula and the habenula commissure. This RFP-MT₁ transgenic model provides a unique tool for studying the distribution of the MT₁ receptor in the brain of mice, its cell-specific expression and its function in vivo.     

Isolation and characterization of polymorphic microsatellite markers from European pear (Pyrus communis L.)

This study reports the development and characterization of 19 microsatellite primer pairs developed from genomic DNA of European pear (Pyrus communis) and their transferability to other Pyrus and Malus material. The primers were designed from two different genomic libraries enriched for di‐ and trinucleotide repeats. When tested in six P. communis cultivars and 15 other Pyrus species, 13 primers revealed single‐locus polymorphism and six showed more complex patterns that suggest multiple loci. Two to 18 alleles were detected per locus and two primer pairs were sufficient to discriminate all accessions. Transferability of nine primer pairs to Malus was demonstrated through amplification of discrete products in two accessions.     

Portasomes as Coupling Factors in Active Ion Transport and Oxidative Phosphorylation

SYNOPSIS. We propose that particles, 7–15 nm in diameter,observed on the apical plasma membranes of cation transportingcells of insect midgut, salivary glands, and Malpighian tubulesare modified F₁-F₀ coupling complexes such as those found onphosphorylating membranes of mitochondria, chloroplasts, andbacteria. We suggest the generic term, portasome, to describeall of these particles and point out that they are located onthe side of the membrane which is electronegative and has thelow cation concentration, i.e., on the input side in each case.Biophysical evidence identifies the portasome bearing membraneas the ion transporting membrane in several insect epithelia,some of which exhibit ion modulated ATPase activity. The activityof a K⁺-modulated ATPase from Manduca sexta midgut is increasedin portasome enriched plasma membrane fractions. We proposethat portasomes orient the scalar hydrolysis of negatively chargedMgATP^2– to less negatively charged MgADP thereby eliminatingthe attraction of MgATP^2– to K⁺ with the result that theK⁺ ions are ejected to the opposite side of the portasome bearingmembrane. This mechanism explains the coupling of the scalarhydrolysis of ATP to the vectorial active transport of K⁺ whichleads to the establishment of a K⁺ electrochemical gradient.The reverse process, but with an H⁺ ionophore replacing a K⁺ionophore in the portasome, would provide a mechanism for couplingthe vectorial flow of H⁺, driven by a proton electrochemicalgradient, to scalar ATP synthesis and thereby provide a mechanismfor oxidative phosphorylation. Electrogenic active potassiumion transport would appear to have evolved from oxidative phosphorylation.     

Vomeronasal/accessory olfactory system and pheromonal recognition

Pregnancy block in mice requires exposure of recently mated females to urinary pheromones of a strange male, and when working with inbred strains this invariably requires urine from an outbred line. The pheromones which induce oestrus and early puberty in mice have been identified as the brevicomins and dihydrothiazoles. Since the same vomeronasal, neural and neuroendocrine pathways are also activated in pregnancy block, these compounds are likely candidates for pregnancy blocking pheromones. However, these relatively simple chemicals lack the capacity to code for differing mouse strains. Since large quantities of the polymorphic major urinary proteins from the lipocalin family found in urine serve as transporters for the dihydrothiazoles and brevicomins, and differ across strains, then these proteins must participate in pheromone recognition in the context of pregnancy block.      

Host activity and wasp experience affect parasitoid wasp foraging behaviour and oviposition on nematode‐infected larvae of the forestry pest Hylobius abietis

1. Entomopathogenic nematodes (EPN) are currently being used as introduced biological control agents against the larvae of the native European forestry pest Hylobius abietis L. which develop under the bark of stumps and roots of newly dead conifer trees. 2. The potential for resource competition between gregarious ectoparasitoid Bracon hylobii Ratz and EPN by recording oviposition and related behaviours of B. hylobii females on EPN‐infected H. abietis larvae was investigated. Wasps did not parasitise EPN‐infected host larvae that were dead when presented, but naÏve and experienced wasps parasitised live EPN‐infected hosts. NaÏve wasps parasitised live EPN‐infected hosts significantly less frequently than healthy hosts only when the infected larvae were close to death (i.e. died during 24‐h trial). Parasitism by experienced wasps was unaffected by host infection. 3. Wasp probing and oviposition were positively associated with the amount of host movement. Preventing H. abietis larvae from chewing on bark significantly reduced parasitism by naÏve, but not experienced wasps. 4. The number of eggs per clutch was not affected by bark chewing or EPN‐infection of H. abietis larvae. 5. NaÏve and experienced B. hylobii parasitised two abnormal hosts (larvae of coleopteran Rhagium bifasciatum Fabricius and lepidopteran Galleria mellonella L.), both of which moved and chewed on bark during trials. 6. It was concluded that B. hylobii can use vibrational cues generated by host movement and feeding to locate hosts at short range and accepts unsuitable (EPN‐infected or abnormal) hosts as long as these create such cues. The implications for competition between B. hylobii and EPN and possible ways of minimising it when applying EPN are discussed.