Approach and following behaviour of 24-hr old chicks as a function of stimulus complexity.

In a straight runway, following or approach behaviour of day-old broiler and leghorn chicks was found to be mainly a linearly decreasing function of stimulus complexity. The patterned stimuli used were checkerboard-like matrices containing, on the average, 4, 36, 100, 400, or 900 bits of information. Preference for simpler stimuli was not found to depend upon experience in the test situation nor upon the degree of complexity of the home pen. When stimulus illuminance was varied, there was a tendency for a plain grey square (zero bits) to be preferred over the pattern containing 4 bits of information, suggesting that approach or following behaviour is energized maximally by some optimal combination of stimulus illuminance and complexity.     

Bruton's Tyrosine Kinase (BTK) and Vav1 Contribute to Dectin1-Dependent Phagocytosis of Candida albicans in Macrophages

Phagocytosis of the opportunistic fungal pathogen Candida albicans by cells of the innate immune system is vital to prevent infection. Dectin-1 is the major phagocytic receptor involved in anti-fungal immunity. We identify two new interacting proteins of Dectin-1 in macrophages, Bruton''s Tyrosine Kinase (BTK) and Vav1. BTK and Vav1 are recruited to phagocytic cups containing C. albicans yeasts or hyphae but are absent from mature phagosomes. BTK and Vav1 localize to cuff regions surrounding the hyphae, while Dectin-1 lines the full length of the phagosome. BTK and Vav1 colocalize with the lipid PI(3,4,5)P₃ and F-actin at the phagocytic cup, but not with diacylglycerol (DAG) which marks more mature phagosomal membranes. Using a selective BTK inhibitor, we show that BTK contributes to DAG synthesis at the phagocytic cup and the subsequent recruitment of PKCε. BTK- or Vav1-deficient peritoneal macrophages display a defect in both zymosan and C. albicans phagocytosis. Bone marrow-derived macrophages that lack BTK or Vav1 show reduced uptake of C. albicans, comparable to Dectin1-deficient cells. BTK- or Vav1-deficient mice are more susceptible to systemic C. albicans infection than wild type mice. This work identifies an important role for BTK and Vav1 in immune responses against C. albicans.     

502. Sinningia Pusilla

Summary. A miniature gesneriad, Sinningia pusilla(C. Mart.) Baill. from Brazil is described and illustrated, and notes are given on the horticultural history of the genus Sinningia     

Wet electron microscopy with quantum dots

Wet electron microscopy (EM) is a new imaging method with the potential to allow higher spatial resolution of samples. In contrast to most EM methods, it requires little time to perform and does not require complicated equipment or difficult steps. We used this method on a common murine macrophage cell line, IC-21, in combination with various stains and preparations, to collect high resolution images of the actin cytoskeleton. Most importantly, we demonstrated the use of quantum dots in conjunction with this technique to perform light/electron correlation microscopy. We found that wet EM is a useful tool that fits into a niche between the simplicity of light microscopy and the high spatial resolution of EM.