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Biomedical subjects

T C Fletcher

Publications and source records attributed to T C Fletcher.

40 records · Page 3Linked to original sources
PubMedDate not supplied

Agglutinin activity in Pacific oyster (Crassostrea gigas) hemolymph following in vivo Vibrio anguillarum challenge.

Hemolymph from the Pacific oyster (Crassostrea gigas) contains lectins that agglutinate horse (Gigalin E) and human (Gigalin H) erythrocytes. The gigalins also agglutinate bacteria, including Vibrio anguillarum, and were adsorbed from oyster hemolymph at different temperatures by living, heat-killed, and freeze-dried V. anguillarum cells. Baseline activities of the two gigalins were established by measuring their activities in oyster hemolymph over a period of 4 years. A normal distribution of Gigalin H activity (mean titer 139) was found, whereas the distribution of Gigalin E activity in the same samples was skew (mean titer 512). No covariance was observed between the two agglutinin activities. Increased lectin activity above this baseline was found in oysters exposed for varying time intervals to V. anguillarum at different seasons and temperatures over a period of 2 years. Such exposure resulted in an increase in activity (titer) of four- to nine-fold for Gigalin E and three- to seven-fold for Gigalin H when compared with controls, and in augmentation in the hemolymph of a protein with the same electrophoretic mobility as affinity-purified oyster lectins (gigalins). Challenge with either living or heat-killed bacteria resulted in a significant increase of Gigalin E activity, whereas results for Gigalin H were variable. Oysters challenged with bacteria were observed to filter normally with open shells during the experiments. Also, no increase was found in hemolymph calcium that could indicate anoxia following bacterial challenge (0.49 +/- 0.004 mg mL-1) compared to unexposed oysters (0.50 +/- 0.001 mg mL-1). Increase in the concentration of free amino acids in oyster hemolymph was observed following exposure to bacteria (15.05 mM) and anaerobiosis (13.51 mM) compared to controls (9.06 mM), and changes (in mol %) of individual amino acids differed considerably between hemolymph from animals challenged with bacteria and animals kept anaerobic. The augmented lectin activity in oyster hemolymph, following in vivo exposure to increased bacteria in the seawater, suggests their involvement in enhancing bacterial clearance and defense in the oyster.

Adhesins, Bacterial↗
PubMedDate not supplied

Effect of temperature on macrophage activation and the production of macrophage activating factor by rainbow trout (Oncorhynchus mykiss) leucocytes.

Production of macrophage activating factor (MAF) by rainbow trout leucocytes has been shown to be temperature dependent in vivo and in vitro. Cells from fish held at 14 degrees C and stimulated to produce MAF immediately after isolation were capable of secreting MAF down to 6 degrees C (the lowest temperature tested). However, after 48 h at 6 degrees C, these leucocytes show impaired MAF secretion. Acclimation of fish to low temperatures (7 degrees C) did not recover the inhibitory effects of low in vitro temperatures on MAF production, but if these leucocytes were preincubated at 10 or 18 degrees C for 48 h, MAF was produced from these cells. Interestingly, macrophages isolated from fish kept at 7 or 14 degrees C and cultured at low temperatures (6 degrees C) were responsive to MAF-containing supernatants, and showed a higher relative increase in respiratory burst activity compared with their counterparts cultured at 10 and 18 degrees C. Such observations clearly demonstrate that a major impairment of bactericidal activity at low temperatures resides within the specific immune compartment of fish. The implications for fish health are discussed.

Acclimatization↗