Dimer–monomer equilibrium of human thymidylate synthase monitored by fluorescence resonance energy transfer

An ad hoc bioconjugation/fluorescence resonance energy transfer (FRET) assay has been designed to spectroscopically monitor the quaternary state of human thymidylate synthase dimeric protein. The approach enables the chemoselective engineering of allosteric residues while preserving the native protein functions through reversible masking of residues within the catalytic site, and is therefore suitable for activity/oligomerization dual assay screenings. It is applied to tag the two subunits of human thymidylate synthase at cysteines 43 and 43′ with an excitation energy donor/acceptor pair. The dimer–monomer equilibrium of the enzyme is then characterized through steady‐state fluorescence determination of the intersubunit resonance energy transfer efficiency.     

Catecholaminergic contributions to the neuronal machinery of the olfactory bulb: aftoradiographic, immunohistochemical and evoked feild potential studies

aftographic exeperiments on the localization of radiolabelednoradrenaline, dopamine and dopa, as well as immunohistochemicalstudies on hydroxylase-like activity, are summarized and comparedin both rat and turtle olfactory bulbs. Evoked field potentialstudies on effects of dopamine are also discussed. The histochemicalstudies suggest that dopaminergic periglomerular neurons arethe most significant cellular component of the catecholaminergicsystem in the olfactory bulb of both species. Scattered fluorescentcell group was also present in the internal plexiform layerand superficial granule cell layer of the turtle olfactory bulb.Other fibres, not related to intrinsic bulbar neuronal cellbodies, were also labeled, mostly in the granule cell layerbut also in the external plexiform layer. These might belongto a centrifugal catecholaminergic system from brain stem neurons.In the in vitro turtle olfactory bulb, dopamine and apomorphinedepressed the amplitude of field potentials evoked by a singlevolley in the olfactory nerve or lateral olfactory tract, andreduced the depression and latency of reponses when paired volleywere delivered. It is suggested that catecholaminergic systemsplay a key role in modulating mitral cell activity through actionsin both superficial (glomerular) and deep (granule) layers.This may involve direct actions, or other, non-catecholaminergicinterneurons.     

The importance of location and visual cues during foraging in the German wasp (Vespula germanica F.) (Hymenoptera: Vespidae)

Abstract

The way in which foraging wasps use cues for prey location and choice appears to depend on both the context and on the type of prey. Vespula germanica is an opportunistic, generalist prey forager, and individual wasp foragers often return to hunt at sites of previous hunting success. In this paper, we studied which cues are used by this wasp when relocating a food source. Particularly we analysed the response to a displaced visual cue versus a foraging location at which either honey or cat food had been previously presented. We conclude that location is used over a displaced visual cue for directing wasp hovering, although the landing response is directed differently according to bait type. When wasps are exploiting cat food, location also elicits landing, but if they are exploiting honey, a displaced visual cue elicits landing more frequently than location.     

Anatomy of the antennal dorsal organ in female of Neodryinus typhlocybae (Hymenoptera: Dryinidae): A peculiar sensory structure possibly involved in perception of host vibration

Neodryinus typhlocybae (Hymenoptera: Dryinidae) is a natural enemy of the planthopper Metcalfa pruinosa, which was introduced from North America into Europe and has become established in various regions as a pest species. Vibrational signals play a crucial role in the communication of M. pruinosa, which appears to be exploited by N. typhlocybae. Scanning and transmission electron microscopy have shown that the antennae of N. typhlocybae females have peculiar and complex sensory structures: deep longitudinal grooves that house long sensilla trichodea, termed here “Antennal Dorsal Organs.” Such structures were not present on male antennae. These sensilla extend for the length of the grooves, without contact with the groove cuticle. Their hair shaft is empty and aporous, and inserted into a specialized socket, underneath which there is a cuticular ampulla‐like chamber. Each sensillum is associated with two sensory neurons: one terminates at the proximal end of the dendritic sheath; the other continues into the sensillum sinus and is enclosed in the dendritic sheath. This second sensory neuron then enters the ampulla‐like chamber through the circular opening, and then terminates with a conspicuous tubular body at the shaft base. The possible involvement of this peculiar structure in the context of host recognition mechanism is discussed. J. Morphol. 277:128–137, 2016. © 2015 Wiley Periodicals, Inc.