Ytterbium-doped fibre femtosecond laser offers robust operation with deep and precise microsurgery of C. elegans neurons.

Laser microsurgery is a powerful tool for neurobiology, used to ablate cells and sever neurites in-vivo. We compare a relatively new laser source to two well-established designs. Rare-earth-doped mode-locked fibre lasers that produce high power pulses recently gained popularity for industrial uses. Such systems are manufactured to high standards of robustness and low maintenance requirements typical of solid-state lasers. We demonstrate that an Ytterbium-doped fibre femtosecond laser is comparable in precision to a Ti:Sapphire femtosecond laser (1-2 micrometres), but with added operational reliability. Due to the lower pulse energy required to ablate, it is more precise than a solid-state nanosecond laser. Due to reduced scattering of near infrared light, it can lesion deeper (more than 100 micrometres) in tissue. These advantages are not specific to the model system ablated for our demonstration, namely neurites in the nematode C. elegans, but are applicable to other systems and transparent tissue where a precise micron-resolution dissection is required.

Wasp manipulates cockroach behavior by injecting venom cocktail into prey central nervous system.

The parasitoid wasp Ampulex compressa induces behavioral changes in the cockroach prey by injecting venom into its central nervous system. In contrast to most other venomous predators, the wasp's sting does not induce paralysis. Rather, the two consecutive stings in the thoracic and head ganglia induce three stereotypic behavioral effects. The prey behavior is manipulated in a way beneficial to the wasp and its offspring by providing a living meal for its newborn larva. The first sting in the thorax causes a transient front leg paralysis lasting a few minutes. This paralysis prevents the cockroach from fighting with its front legs, thereby facilitating the second sting in the head. A postsynaptic block of central synaptic transmission mediates this leg paralysis. Following the head sting, dopamine identified in the venom induces 30 minutes of intense grooming that appears to prevent the cockroach from straying until the last and third behavioral effect of hypokinesia commences. In this lethargic state that lasts about three weeks, the cockroach does not respond to various stimuli nor does it initiates movement. However, other specific behaviors of the prey are unaffected. We propose that the venom represses the activity of head ganglia neurons thereby removing the descending excitatory drive to specific thoracic neurons.

Wasp venom blocks central cholinergic synapses to induce transient paralysis in cockroach prey.

The parasitoid wasp Ampulex compressa induces a set of unique behavioral effects upon stinging its prey, the cockroach. It stings into the first thoracic segment inducing 2 to 3 min of transient flaccid paralysis of the front legs. This facilitates a second sting in the cockroach's head that induces 30 min of excessive grooming followed by a 2 to 5-week long lethargic state. In the present study, we examine the immediate effect of the first sting, which is a transient paralysis of the front legs. Using radiolabeled wasps, we demonstrate that the wasp injects its venom directly into the cockroach's first thoracic ganglion. The artificial injection of milked venom into a thoracic ganglion abolishes spontaneous and evoked responses of the motoneurons associated with leg movements. To investigate the physiological mechanism of action of the venom, we injected venom into the last abdominal ganglion of the cockroach, which houses a well-characterized cholinergic synapse. Injected venom abolishes both sensory-evoked and agonist-evoked postsynaptic potentials recorded in the postsynaptic neuron for 2 to 3 min without affecting action potential propagation. Thus, the venom blocking effect has a postsynaptic component that follows the same time course as the transient paralysis induced by the thoracic sting. Finally, injection of a nicotinic antagonist in the front thoracic ganglion induces paralysis of the front legs. We conclude that the transient paralytic effect of the thoracic sting can be mainly accounted for by the presence of a venom active component that induces a postsynaptic block of central cholinergic synaptic transmission.

Venom of a parasitoid wasp induces prolonged grooming in the cockroach

The parasitoid wasp Ampulex compressa hunts cockroaches Periplaneta americana, stinging them first in the thorax and then in the head, the sting penetrating towards the subesophageal ganglion. After being stung the cockroach grooms almost continuously for approximately 30 min, performing all the normal components of grooming behavior. This excessive grooming is only seen after the head sting and cannot be attributed to stress, to contamination of the body surface or to systemic or peripheral effects. This suggests that the venom is activating a neural network for grooming. We suggest that the venom induces prolonged grooming by stimulating dopamine receptors in the cockroach, for the following reasons. (1) Reserpine, which causes massive release of monoamines, induces excessive grooming. (2) Dopamine injected into the hemocoel also induces excessive grooming and is significantly more effective than octopamine or serotonin. In addition, the dopamine agonist SKF 82958 induces excessive grooming when injected directly into the subesophageal ganglion. (3) Injection of the dopamine antagonist flupenthixol greatly reduces venom-induced grooming. (4) Dopamine, or a dopamine-like substance, is present in the venom.

Identification and nucleotide sequence of the Acinetobacter calcoaceticus encoded trpE gene.

The trpE gene from Acinetobacter calcoaceticus encoding the anthranilate synthase component I was cloned, identified by deletion analysis and sequenced. It encodes a predicted polypeptide of 497 amino acids with a calculated molecular weight of 55,323. Its primary structure shows 49% identical amino acids with the enzyme from Clostridium thermocellum, 45% with that of Thermus thermophilus and only 35% with that of Escherichia coli. The codon usage of the trpE genes encoding the most homologous enzymes differs greatly indicating selection for amino acid maintainance. The homologies are clustered in the C-terminal 200 amino acids of the sequences indicating that this part is important for enzymic activity.