Oxytocin enhances gaze-following responses to videos of natural social behavior in adult male rhesus monkeys.

Gaze following is a basic building block of social behavior that has been observed in multiple species, including primates. The absence of gaze following is associated with abnormal development of social cognition, such as in autism spectrum disorders (ASD). Some social deficits in ASD, including the failure to look at eyes and the inability to recognize facial expressions, are ameliorated by intranasal administration of oxytocin (IN-OT). Here we tested the hypothesis that IN-OT might enhance social processes that require active engagement with a social partner, such as gaze following. Alternatively, IN-OT may only enhance the perceptual salience of the eyes, and may not modify behavioral responses to social signals. To test this hypothesis, we presented four monkeys with videos of conspecifics displaying natural behaviors. Each video was viewed multiple times before and after the monkeys received intranasally either 50 IU of OT or saline. We found that despite a gradual decrease in attention to the repeated viewing of the same videos (habituation), IN-OT consistently increased the frequency of gaze following saccades. Further analysis confirmed that these behaviors did not occur randomly, but rather predictably in response to the same segments of the videos. These findings suggest that in response to more naturalistic social stimuli IN-OT enhances the propensity to interact with a social partner rather than merely elevating the perceptual salience of the eyes. In light of these findings, gaze following may serve as a metric for pro-social effects of oxytocin that target social action more than social perception.

120-kD surface glycoprotein of Pneumocystis carinii is a ligand for surfactant protein A.

Pneumocystis carinii is the most common cause of life-threatening pneumonia in immunocompromised patients. In the current study, surfactant protein A (SP-A), the major nonserum protein constituent of pulmonary surfactant, is demonstrated to bind P. carinii in a specific and saturable manner. SP-A is surface bound and does not appear to be internalized or degraded by the P. carinii organism. Furthermore, SP-A binding to P. carinii is time- and calcium-dependent and is competitively inhibited by mannosyl albumin. In the absence of calcium or the presence of excess mannosyl albumin, SP-A binding to P. carinii is reduced by 95 and 71%, respectively. SP-A avidly binds P. carinii with a Kd of 8 x 10(-9) M and an estimated 8.4 x 10(6) SP-A binding sites per P. carinii organism, as determined from Scatchard plots. SP-A is shown to bind P. carinii in vivo, and a putative binding site for SP-A on P. carinii is demonstrated to be the mannoserich surface membrane glycoprotein gp120. These findings suggest that P. carinii can interact with the phospholipid-rich material in the alveolar spaces by specifically binding a major protein constituent of pulmonary surfactant.