Characteristics of development and reproduction in Typhlodromus pyri on Tetranychus urticae and Cecidophyopsis ribis. II. Progeny of overwintered females

The results of this study on the bionomic parameters in progeny of overwintered females of Typhlodromus pyri Scheuten under constant laboratory conditions (18°C, R.H. 75%. 18L:6D) are described. The predatory mites were fed overwintering forms of two prey species, the two-spotted spider mite. Tetranychus urticae Koch and the black currant gall mite. Cecidophyopsis ribis (Westwood). The results corroborate that T. pyri is able to complete its life-cycle and reproduce when it feeds exclusively on the black currant gall mite. Juvenile development of females feeding on T. urticae and on C. ribis was 19.4 and 20.9 days respectively, while in males it was 18.4 and 17.5 days. Mortality of juveniles feeding on T. urticae was higher (33.0%) compared with that of juveniles fed on C. ribis (10.7%). The highest mortality was noted in protonymphs fed on T. urticae (21.9%). The difference between the mean total fecundity of females fed on T. urticae (16.4 eggs) and on C. ribis (17.8 eggs) was not statistically significant. Mean duration of preoviposition, oviposition and postoviposition periods were 19.1, 25.0 and 14.5 days in females fed on T. urticae and 19.7. 50.2 and 5.0 in those fed on C. ribis.     

A taxonomic revision of Tyrini of the Oriental?region. V. Revision of the genus Lasinus Sharp, 1874 (Coleoptera,Staphylinidae, Pselaphinae)

The genus Lasinus Sharp, 1874 of the Pselaphodes complex of genera (Pselaphitae: Tyrini: Tyrina) is revised. The three so far known species, Lasinus mandarinus Raffray, 1890, Lasinus monticola Sawada, 1961 and Lasinus spinosus Sharp, 1874 are redescribed. Eight new species, Lasinus sinicus sp. n. from China, Lasinus mikado sp. n., Lasinus yamamotoi sp. n., Lasinus inexpectatus sp. n., Lasinus yakushimanus sp. n., Lasinus amamianus sp. n., Lasinus saoriae sp. n., and Lasinus okinawanus sp. n. from Japan, are described. And all species are illustrated. Lectotypes are designated for Lasinus mandarinus and Lasinus spinosus. An identification key to species of the genus Lasinus is provided.     

PKC independent inhibition of voltage gated calcium channels by volatile anesthetics in freshly isolated vascular myocytes from the aorta

In this study we used barium currents through voltage gated L-type calcium channels (recorded in freshly isolated cells with a conventional patch-clamp technique) to elucidate the cellular action mechanism for volatile anesthetics. It was found that halothane and isoflurane inhibited (dose-dependently and voltage independently) Ba²⁺ currents through voltage gated Ca²⁺ channels. Half maximal inhibitions occurred at 0.64 ± 0.07 mM and 0.86 ± 0.1 mM. The Hill slope value was 2 for both volatile anesthetics, suggesting the presence of more than one interaction site. Current inhibition by volatile anesthetics was prominent over the whole voltage range without changes in the peak of the current voltage relationship. Intracellular infusion of the GDPβS (100 μM) together with staurosporine (200 nM) did not prevent the inhibitory effect of volatile anesthetics. Unlike pharmacological Ca²⁺ channel blockers, volatile anesthetics blocked Ca²⁺ channel currents at resting membrane potentials. In other words, halothane and isoflurane induced an ‘initial block’. After the first 4–7 control pulses, the cells were left unstimulated and anesthetics were applied. The first depolarization after the pause evoked a Ca²⁺ channel current whose amplitude was reduced to 41 ± 3.4% and to 57 ± 4.2% of control values. In an analysis of the steady-state inactivation curve for voltage dependence, volatile anesthetics induced a negative shift of the 50% inactivation of the calcium channels. By contrast, the steepness factor characterizing the voltage sensitivity of the channels was unaffected. Unitary L-type Ca²⁺ channels blockade occurred under cell-attached configuration, suggesting a possible action of volatile anesthetics from within the intracellular space or from the part of the channel inside the lipid bilayer.     

Up-regulation of GABAB Receptor Signaling by Constitutive Assembly with the K+ Channel Tetramerization Domain-containing Protein 12 (KCTD12)

GABA_B receptors are the G-protein coupled receptors (GPCRs) for GABA, the main inhibitory neurotransmitter in the central nervous system. Native GABA_B receptors comprise principle and auxiliary subunits that regulate receptor properties in distinct ways. The principle subunits GABA_B1a, GABA_B1b, and GABA_B2 form fully functional heteromeric GABA_B(1a,2) and GABA_B(1b,2) receptors. Principal subunits regulate forward trafficking of the receptors from the endoplasmic reticulum to the plasma membrane and control receptor distribution to axons and dendrites. The auxiliary subunits KCTD8, -12, -12b, and -16 are cytosolic proteins that influence agonist potency and G-protein signaling of GABA_B(1a,2) and GABA_B(1b,2) receptors. Here, we used transfected cells to study assembly, surface trafficking, and internalization of GABA_B receptors in the presence of the KCTD12 subunit. Using bimolecular fluorescence complementation and metabolic labeling, we show that GABA_B receptors associate with KCTD12 while they reside in the endoplasmic reticulum. Glycosylation experiments support that association with KCTD12 does not influence maturation of the receptor complex. Immunoprecipitation and bioluminescence resonance energy transfer experiments demonstrate that KCTD12 remains associated with the receptor during receptor activity and receptor internalization from the cell surface. We further show that KCTD12 reduces constitutive receptor internalization and thereby increases the magnitude of receptor signaling at the cell surface. Accordingly, knock-out or knockdown of KCTD12 in cultured hippocampal neurons reduces the magnitude of the GABA_B receptor-mediated K⁺ current response. In summary, our experiments support that the up-regulation of functional GABA_B receptors at the neuronal plasma membrane is an additional physiological role of the auxiliary subunit KCTD12.     

Heterotopic cardiomyocytes in the wall of pulmonary vessels in experimental animals

Heterotopic cardiomyocytes (CMC) have been described in the wall of pulmonary veins including intraparenchymatous branches, in various species of laboratory animals. Brief note is given here of their morphology including electron microscopy and immunohistological findings. From the current literature hints concerning arrhythmogenic activity of heterotopic CMC in pulmonary vessels in the possible initiation of atrial tachyarrhythmia and fibrillation are also mentioned.     

Interactions in a tritrophic acarine predator-prey metapopulation system IV: effects of host plant condition on Tetranychus urticae (Acari: Tetranychidae)

Feeding by spider mites can cause severe injury to a host plant and lead to a decreasing per capita growth rate and an increasing per capita emigration rate. Such density-dependent responses to local conditions are important in a metapopulation context because they allow the herbivores to colonize new host plants and thereby prolong the time until regional (metapopulation) extinction. In order to include density-dependent responses of the two-spotted spider mite (Tetranychus urticae) in a realistic metapopulation model, a series of greenhouse experiments was conducted with the purpose to quantify how the condition of bean plants (Phaseolus vulgaris) influences the demographic parameters of T. urticae. Plant age per se reduced the growth rate of the spider mites only slightly, whereas the growth rate declined significantly as the plants were injured by the mites. The relationships between plant condition (expressed by the plant injury index D) and the birth and loss (death + emigration) rates of the mites were quantified so as to predict population growth as a function of D. Maximum per capita growth rate (r) was estimated to be c. 0.21 day⁻¹. The growth rate is expected to be negative when D exceeds 0.8. When mites were allowed to emigrate to neighbouring plants via bridges, the per capita emigration rate increased almost exponentially with D. The proportion of eggs in the population decreased with D while the numerical ratio between immatures to adults and the sex ratio did not change with D. Overall, immatures and adults constituted 74% and 26%, respectively, of the active mites and c. 46% of the adults were males. The bridges that connected a donor plant with the surrounding recipient plants were responsible for the majority of the emigrations from donor plants. Most mites stopped after having crossed a single bridge, but a few crossed two bridges while none crossed three bridges within 24 h. The significance of the results for biological control is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Wing morph-related physiological differences in adults of temperate population of Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae)

The reproductive and diapausing adult females of brachypterous morph and macropterous females with reproductive arrest of non-diapause type, originating from the laboratory cultures of Pyrrhocoris apterus, were studied for their feeding and drinking behaviour, digestive enzyme activities, and carbohydrate and lipid contents. The highest feeding and drinking activities were observed in reproductive brachypters, the lowest in macropters. Macropters also differed from brachypters by lower activities of gut lipase, peptidase and protease, lower concentration of haemolymph sugars, and lower weight of fat body, which probably reflects their low feeding activity. The total content of fat body lipids was also lower in macropters (0.6 mg) than in reproductive and diapausing brachypters (4.6 and 7.5 mg, respectively) on day 14. A very high amount of glycogen was found in the fat body of diapausing brachypters, 363 μg on day 14, as opposed to 15 and 80 μg in macropterous and reproductive brachypterous females, respectively. The obtained data indicate that the most important difference between macropterous and brachypterous females with different types of reproductive arrest consists of an enhanced mobilization of lipids for dispersal in macropters and accumulation of energetic reserves for hibernation in brachypters.     

Molecular organization and dynamics of the melatonin MT1 receptor/RGS20/Gi protein complex reveal asymmetry of receptor dimers for RGS and Gi coupling

Functional asymmetry of G‐protein‐coupled receptor (GPCR) dimers has been reported for an increasing number of cases, but the molecular architecture of signalling units associated to these dimers remains unclear. Here, we characterized the molecular complex of the melatonin MT₁ receptor, which directly and constitutively couples to G_i proteins and the regulator of G‐protein signalling (RGS) 20. The molecular organization of the ternary MT₁/G_i/RGS20 complex was monitored in its basal and activated state by bioluminescence resonance energy transfer between probes inserted at multiple sites of the complex. On the basis of the reported crystal structures of G_i and the RGS domain, we propose a model wherein one G_i and one RGS20 protein bind to separate protomers of MT₁ dimers in a pre‐associated complex that rearranges upon agonist activation. This model was further validated with MT₁/MT₂ heterodimers. Collectively, our data extend the concept of asymmetry within GPCR dimers, reinforce the notion of receptor specificity for RGS proteins and highlight the advantage of GPCRs organized as dimers in which each protomer fulfils its specific task by binding to different GPCR‐interacting proteins.     

Intracellular cAMP: the "switch" that triggers on "spontaneous transient outward currents" generation in freshly isolated myocytes from thoracic aorta

Spontaneous transient outward currents (STOCs) have been reported in resistance and small arteries but have not yet been found in thoracic aorta. Do thoracic aorta myocytes possess cellular machinery that generates STOCs? It was found that the majority of aortic myocytes do not generate STOCs. STOCs were generated in 8.7% of freshly isolated aortic myocytes. Myocytes that did not generate STOCs we have called "silent" myocytes and myocytes with STOCs have been called "active." STOCs recorded in active myocytes were voltage dependent and were inhibited by ryanodine, caffeine, and charybdotoxin. Forskolin was reported to increase STOCs frequency in myocytes isolated from resistance arteries. Forskolin (10 microM) triggered STOCs generation in 35.1% of silent aortic myocytes. In 36.8% percent of silent myocytes, forskolin did not trigger STOCs but increased the amplitude of charybdotoxin-sensitive outward net current to 136.1 +/- 8.5% at 0 mV. Membrane-permeable 8BrcAMP triggered STOCs generation in 38.7% of silent myocytes. Forskolin- or 8BrcAMP-triggered STOCs were inhibited by charybdotoxin. 8BrcAMP also increased open probability of BK(Ca) channels in BAPTA-AM-pretreated cells. Our data demonstrate that, in contrast to resistance arteries, STOCs are present just in the minority of myocytes in the thoracic aorta. However, cellular machinery that generates STOCs can be "switched" on by cAMP. Such an inactive cellular mechanism could modulate the contractility of the thoracic aorta in response to physiological demand.