Neuroendocrine mechanisms underlying sensory integration of social signals.

Individuals integrate information about their environment into adaptive behavioural responses, yet how different sensory modalities contribute to these decisions and where in the brain this integration occurs is not well understood. We presented male cichlid fish (Astatotilapia burtoni) with sensory information in three social contexts: intruder challenge, reproductive opportunity and a socially neutral situation. We then measured behavioural and hormonal responses along with induction of the immediate early gene c-Fos in candidate forebrain regions. In the intruder challenge context, males were exposed to either a visual stimulus of a dominant male, the putative male pheromone androstenedione, or both. We found that, compared to the neutral context, a visual stimulus was necessary and sufficient for an aggressive response, whereas both chemical and visual stimuli were needed for an androgen response. In the reproductive opportunity context, males were exposed to either a visual stimulus of a receptive female, a progesterone metabolite (female pheromone) only, or both. We further found that the visual stimulus is necessary and sufficient for an androgen response in the reproductive opportunity context. In the brain, we observed c-Fos induction in response to a visual challenge stimulus specifically in dopaminergic neurones of area Vc (the central region of the ventral telencephalon), a putative striatal homologue, whereas presentation of a chemical stimulus did not induce c-Fos induction in the intruder challenge context. Our results suggest that different sensory cues are processed in a social context-specific manner as part of adaptive decision-making processes.

Bacterial Florae in Larvae of the Lake Fly Chironomus plumosus.

Chironomus plumosus midge larvae were collected from Lake Winnebago, Wisconsin, for 10 weeks in the summer of 1985 and 10 weeks in the summer of 1986 in order to determine their bacterial floras. Altogether, 18 genera and 29 species of bacteria were found and identified. Some spirillum-like bacteria which were not isolated in culture were found by electron microscopy. Scanning electron micrographs of sectioned larvae revealed bacteria throughout the intestines. Gram-positive organisms were most prevalent in the larvae in the early part of the summer, and gram-negative organisms were most prevalent during the later part. Larvae accumulate bacteria within their intestines.

Pathogenicity ofAeromonas hydrophila in red leg disease in frogs.

Endotoxin and hemolysin fromAeromonas hydrophila A(3) were studied to understand the pathogenicity of the organism. Neither the endotoxin nor the hemolysin alone produced typical red leg disease symptoms or death in frogs, even at a very high dosage of 8,000 µg; however, endotoxin and hemolysin together did. Further, histamine-stressed frogs died from hemolysin but not endotoxin. Hemolytic activity of hemolysin increased in cells that were preincubated with endotoxin. Results point to the conclusion that red leg disease in frogs represents a complex interaction between endotoxin and hemolysin and that stress-producing factors other than the endotoxin might trigger disease production.

Growth temperatures and temperature characteristics of Aeromonas.

Six of the 13 Aeromonas hydrophila, 1 of 10 A. shigelloides, and none of 10 A. salmonicida were found to be psychrophiles. All of the rest of the strains were mesophiles. The mu values (temperature characteristics) could not be used to distinguish psychrophiles from mesophiles.

Amino acid requirements of Aeromonas.

Four of the 12 cultures of Aeromonas hydrophila, 5 of the 10 A. shigelloides, and 9 of the 10 A. salmonicida that were studied required arginine and lysine, among other amino acids, for their growth.

Characteristics of the Hemagglutinin Produced During Plasmodium lophurae Malaria in Chickens.

During the course of Plasmodium lophurae infections in normal chickens, there was a sharp increase in the titer of a hemagglutinin which reacted better with trypsinized than with normal erythrocytes. This hemagglutinin was a typical "cold hemagglutinin" in that it was much more active at 4 C than at 37 C, was found in the macroglobulin fraction of the serum, was eluted from erythrocytes at 37 C, and was easily destroyed by 2-mercaptoethanol reduction. The injection of allogeneic erythrocytes into chickens prior to their exposure to P. lophurae resulted in a coexistent increase in cold hemagglutinin titers and enhanced resistance to parasitemia. Since this antibody was more active against altered erythrocytes than against normal erythrocytes, it may moderate resistance to malarial infections by specifically stimulating phagocytosis of parasitized erythrocytes.