The inebri-actometer: a device for measuring the locomotor activity of Drosophila exposed to ethanol vapor.

Drosophila melanogaster can be used as a model organism for probing the genetic basis for alcohol sensitivity. In this paper, we describe a new device, the inebri-actometer, which measures the locomotor activity of up to 128 individual flies simultaneously. The device consists of 128 pairs of emitter/detector photodiodes connected in series through a computer interlink. A single fly is placed in each of the 128 chambers and humidified air or air containing variable amounts of ethanol vapor is pumped through the chambers. When a fly blocks the infrared signal transmitted by an emitter photodiode, the computer records one movement for that fly. We present preliminary results showing the effect of ethanol on the activity of wild-type Oregon R Drosophila. Five preliminary runs with 95% ethanol vapor revealed that this concentration induces an approximately 3- to 4-fold increase in locomotor activity which peaks at about 5 min after the addition of ethanol vapor. This is followed by a gradual decrease in activity leading to a nearly total cessation of movement after 30 min. Statistically significant dose-related activity increases were obtained for ethanol concentrations of 8, 19, 50, and 100% of maximum, assessed in two replications at each dose. Unlike the complete suppression of locomotion seen in the last 10 min of the session at maximum ethanol exposure, the initial stimulation effect at the 19% concentration was maintained across the 30-min session.

Inexpensive, semi-automated system for measuring mechanical properties of soft tissues.

Stiffness and strength are important properties of many tissues, but standard material-testing equipment is expensive, often ill-suited for testing soft tissues, and rarely accessible to biologists. We describe a system built around a microcomputer and an electronic balance which is particularly well-suited for measuring stress and strain in small samples of soft tissue. We use a discarded floppy disk drive as a linear actuator to strain the sample, while an electronic balance measures the tension (used to calculate stress). We give an algorithm for a program to drive a microcomputer which controls the floppy disk drive via its parallel port and records the balance measurements via its serial port. We used this system to obtain stress-strain curves from a sample of latex rubber and a sample of soft insect cuticle. Three tests of the rubber sample gave nearly identical results, with smooth, J-shaped stress-strain curves. The stress-strain curves gave a modulus elasticity value of 1.72 Mpa over the steep, straight region, well within the range for natural latex rubber. We also tested a sample of abdominal cuticle from a caterpillar (Manduca sexta). The caterpillar cuticle had a J-shaped stress-strain curve with a modulus of elasticity of 2.11 Mpa over the steep part of the curve. J. Exp. Zool. 284:374-378, 1999.