A simple remote-controlled power switch for internalized bioelectronic instrumentation.

This communication presents a remote-controlled power switch for extending the battery life of biomedical instruments implanted into animals or humans. The switching action is controlled externally to the implant by an inductive link between two coils, one contained in the implant and one external to the implant. The external coil sends an electromagnetic pulse to the implant, triggering a CMOS "D" flip-flop connected as a toggle switch--its state is toggled on or off upon receiving the external pulse. The standby current drain of the switch is about 4 nA. The remote triggering range is approximately 20-50 cm. Testing of the switch, surgically implanted as part of a telemetry transmitter, is also discussed.

Technical note: a noninvasive procedure for measuring goat heart rates.

Heart rates were obtained simultaneously from FM radio transmitters and heart rate monitors externally mounted on unanesthetized and unrestrained mixed-breed goats. Data from transmitters were highly correlated (r = .92, P < .0001) with data from monitors and the percentage difference in heart rates between the two devices was less than that observed between animals. Analyses also revealed that radio transmitters provided a reliable, repeatable, and valid method for the noninvasive measurement of goat heart rates.

A simplified telemetry system for monitoring body temperature in small animals.

An inexpensive but reliable telemetry system for long-term, sequential monitoring of body temperature in up to 20 laboratory animals is described. The system consists of frequency-modulated (FM) temperature transmitters, remote-controlled power switches to extend battery life, a multi-channel telemetry receiver, and a frequency counter interfaced with a personal computer to record data. Analysis of body temperature data obtained from four New Zealand White rabbits confirms the reliability and value of this system.

Intracellular calcium increases with hyperactivation in intact, moving hamster sperm and oscillates with the flagellar beat cycle.

At some time before fertilization, mammalian sperm undergo a change in movement pattern, termed hyperactivation. There is evidence that hyperactivation offers an advantage to sperm for detaching from the oviductal mucosa, for penetrating viscoelastic substances in the oviduct, and for penetrating the zona pellucida. Hyperactivation is known to require extracellular calcium, but little else is known about the mechanisms by which calcium affects sperm movement. The calcium-sensitive fluorescent dye indo-1 was used to follow intracellular calcium levels ([Ca2+]i) in individual moving sperm. Sperm were loaded with 10 microM of the acetoxymethyl ester form of the dye and then rinsed. The dye was excited at 340 nm by using a filtered xenon stroboscope, and images at the 405-nm and 490-nm excitation maxima were simultaneously digitized at 30 per sec for 2.1 sec. [Ca2+]i was significantly higher in the acrosomal and postacrosomal regions of the head and in the flagellar midpiece (the principal piece could not be measured) in hyperactivated than in nonhyperactivated sperm (P < 0.0001). [Ca2+]i oscillations were detected in the proximal half of the midpiece that were identical in frequency to the flagellar-beat-cycle frequency in 12 of 17 hyperactivated sperm (median, 3.5 Hz). Rapid [Ca2+]i oscillations were also detected in the acrosomal and postacrosomal regions, as well as in the distal midpiece. Oscillations were not eliminated by dampening the flagellar bending with methyl cellulose. The [Ca2+]i oscillations detected in sperm are significantly more rapid than oscillations detected in other cell types.