The copulatory performance of male rats, tested in a large seminaturalistic environment, was assessed to determine the relation between 22-kHz ultrasonic vocalizations and a range of sociosexual behaviors. The male rats were tested until sexual exhaustion. Such ultrasonic signals were shown to occur in a wider range of sociosexual circumstances than previously reported; for example, the calls occurred in particular social circumstances during the preejaculatory period as well as during the postejaculatory interval. There was no consistent evidence that the emission of this call during the postejaculatory period consistently functions to keep the female away from the male. The nature and occurrence of postejaculatory ultrasonic signals showed increasing variability in successive ejaculatory series. The results of this and previous studies are interpreted within a semiotic theory of communication. The 22-kHz call is described as a message that makes available the information that the sender is in a socially depressed and withdrawn state.

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The effects of a new transfusion filter (Swank IL-20U) on stored, whole blood have been examined. Six filters were preloaded by passage of two units of outdated, type-specific bank blood, and the effects of filtration on a third unit of 21-day-old blood flowing under 150 mm Hg pressure were measured. Filtration did not significantly alter erythrocyte or leukocyte count, total or plasma hemoglobin, red-cell fragility, and plasma sodium, potassium, albumin, or globulin. Platelet counts were reduced by 33%. Removal of microaggregates, assessed by Coulter counting, screen filtration pressure, total screen protein, wet and dry weight of material retained, and scanning electron microscopy, was shown to be effective over the entire range of particle size. In comparison with other transfusion filters previously examined in this laboratory, the Swank IL-201 filter combines the features of efficient microaggregate removal with moderate blood-flow rate. Compared to its predecessor, the Swank IL-200, this new filter design has improved flow characteristics without loss of microaggregate removal efficiency. In view of the similarity of performance demonstrated for several of the available filters, it seems likely that relative cost will constitute an important determinant of filter selection.

No abstract