Conscious awareness is necessary to assess trust and mimic facial expressions, while pupils impact trust unconsciously.

People make rapid inferences about others' thoughts and intentions. For example, they observe facial movements and pupil size of others and unwittingly make use of this information when deciding whether to trust someone or not. However, whether spontaneous mimicry depends on visual awareness of the stimulus and whether these processes underlie trust decisions is still unknown. To investigate whether visual awareness modulates the relationship between emotional expressions, mimicry and trust, participants played a series of trust games and saw either their partners' faces with a neutral, happy or fearful expression, or their partners' eyes in which the pupil size was large, medium or small. Subjects' trust investments, facial movements and pupil responses were measured. In half of the trials, the stimuli were rendered invisible by continuous flash suppression. Results showed that facial expressions were mimicked and influenced trust decisions during the conscious condition, but not during the unconscious (suppressed) condition. The opposite was found for pupil size, which influenced trust decisions during states of unawareness. These results suggest that the neurobiological pathway linking the observation of facial expressions to mimicry and trust is predominantly conscious, whereas partner pupil size influences trust primarily when presented unconsciously. This article is part of the theme issue 'Cracking the laugh code: laughter through the lens of biology, psychology and neuroscience'.

Blood grouping with monoclonal anti-N antibodies.

Four monoclonal antibodies (N1, N3, N4 and N5) with specificity for the N blood group have been produced from fusions in which human erythrocytes were used as the immunizing stimulus. N1 and N3 differed from N4 and N5 with regard to their serological specificities and pH optima. Antibody N3 has been assessed for its suitability as a blood grouping reagent by testing 10,767 blood donors in parallel with Vicia graminea anti-N lectin or rabbit anti-N. There was complete correlation between the results obtained with the monoclonal and conventional reagents providing strong evidence that N3 is a reliable and potent blood grouping reagent.

Monoclonal antibodies specific for blood groups A and B.

Monoclonal antibodies have been produced with specificity for human blood group A following the immunization of mice with group A1 cells. The antibodies produced were of low titre and poor avidity and were therefore unsuitable as manual grouping reagents. However, in 6,524 automated tests on the Technicon BG15 monoclonal anti-A performed as well as the standard human anti-A reagent. Monoclonal anti-B antibodies were produced from a BALB/c mouse immunized with a combination of group B cells and B substance. One antibody, B/C9/F7, performed well in screening tests with avidity reactions less than 10 seconds with all B, A1B and A2B cells tested. This antibody performed with 100% accuracy in an automated test trial involving 1,018 samples. The suitability of these antibodies as blood grouping reagents is discussed.

Evidence that the arginine esteropeptidase (gamma) subunit of nerve growth factor can activate inactive renin.

The beta and gamma subunits of nerve growth factor were isolated and tested for inactive-renin-activating activity using human amniotic fluid as a convenient source of inactive renin. Only the gamma subunit, which is an arginine esteropeptidase, could activate inactive renin. The role of this enzyme in sites containing both it and inactive renin warrants investigation.

Renin in mouse but not in rat submandibular glands.

Renin was found in the submandibular glands of male Quackenbush mice in concentrations higher than has been reported for any tissue of any strain or species. However, no renin-like activity could e detected in glands from male and female Wistar rats using either pH 5.8 or 7.4 for assay and a radioimmunoassay specific for renin's reaction product, angiotensin I. Rabbit submandibular glands contained renin.