Click communication in wild harbour porpoises (Phocoena phocoena).

Social delphinids employ a vocal repertoire of clicks for echolocation and whistles for communication. Conversely, the less social and acoustically cryptic harbour porpoises (Phocoena phocoena) only produce narrow-band high-frequency (NBHF) clicks with properties that appear poorly suited for communication. Nevertheless, these small odontocetes likely mediate social interactions, such as mate choice and mother-calf contact, with sound. Here, we deployed six tags (DTAG3) on wild porpoises in Danish waters for a total of 96 hours to investigate if the patterns and use of stereotyped NBHF click trains are consistent with a communication function. We show that wild porpoises produce frequent (up to 27 • min-1), high-repetition rate click series with repetition rates and output levels different from those of foraging buzzes. These sounds are produced in bouts and frequently co-occur with emission of similar sounds by nearby conspecifics, audible on the tags for >10% of the time. These results suggest that social interactions are more important to this species than their limited social encounters at the surface may indicate and that these interactions are mediated by at least two broad categories of calls composed of short, high-repetition rate click trains that may encode information via the repetition rate of their stereotyped NBHF clicks.

A radioactive assay for the physiological activity of the tryptophan synthetase alpha subunit in crude extracts of Escherichia coli.

A modified assay has been devised for the physiological reaction, indole-3-glycerol phosphate to Trp, of the enzyme tryptophan synthetase. The assay may be applied to crude bacterial extracts, and is based on the measurement of incorporation of radioactivity from [3H]Ser into Trp. Comparison with previous colorimetric assays indicates an improvement in sensitivity of about 30-fold, and advantages in terms of sample economy and simplified manipulation.

Oxygen and glucose consumption related to Na+-K+ transport in canine brain.

This study examines the relation between Na+-K+ transport and metabolism in the canine brain. Cerebral oxygen and glucose consumption was measured by the sagittal sinus outflow technique. Synaptic transmission and related metabolism was blocked by pentobarbital 40 mg/kg (EEG flat). Lidocaine blocked an additional 15-20%, presumable by restricting Na+-K+ leak fluxes and reducing the demand for Na+-K+ transport. Ouabain blocked an additional 20-25% of metabolism. Ouabain also inhibited the Na+-K+ sensitive ATPase associated transport and caused a net efflux of K+ from the cellular compartment as evidenced by an increasing extracellular K+ concentration in the cortex. Accordingly, a total of 40% of metabolism in te EEG-arrested barbiturate inhibited brain could be related to Na+-K+ leak fluxes and associated transport. The remaining 60% are related to processes unidentified by this study. It is concluded that cerebral metabolism may be reduced below the hitherto described barbiturate minimum.

Inhibition of cerebral oxygen and glucose consumption in the dog by hypothermia, pentobarbital, and lidocaine.

The effect of lidocaine, 160 mg/kg, and pentobarbital, 40 mg/kg, on cerebral oxygen and glucose consumption was examined at brain temperatures of 37 degrees C, 28 degrees C, and 18 degrees C. Cerebral metabolic rate was measured in dogs on cardiopulmonary bypass circulation by using the sagittal sinus outflow technique. When studied separately, both drugs suppressed synaptic transmission and inhibited metabolism, and a maximum effect was obtained when the EEG became flat. Using halothane 1-1.5 per cent as the control condition, this function-metabolism coupled inhibition was about 30 per cent. When the drugs were studied in combination, it was found that when lidocaine was given after pentobarbital, it caused an additional metabolic inhibition of 15-20 per cent, while pentobarbital given after lidocaine had no effect. It is concluded that pentobarbital has no inhibitory effect on cerebral metabolism in the absence of synaptic activity, while lidocaine--in addition to the effect related to suppression of synaptic transmission--has a specific "membrane stabilizing" effect. In analogy to its local anesthetic action, lidocaine blocks the Na+ channels and restricts the Na+-K+ leak fluxes. The load on the ion pump is reduced and metabolism is decreased accordingly. This specific effect on lidocaine was evident also at brain temperatures of 28 degrees C and 18 degrees C. The study supports the possibility that lidocaine, like hypothermia, may provide protection for the ischemic brain.