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Spectral characteristics of isolated blowfly calliphora erythrocephala rhabdoms






Journal of Comparative Physiology A Sensory Neural & Behavioral Physiology 155(1): 47-56

Spectral characteristics of isolated blowfly calliphora erythrocephala rhabdoms

A rapid and simple method for the isolation of rhabdoms from the eye of the blowfly Calliphora erythrocephala Meig. is described. Essentially this involves the excision of the retina, then its disintegration using a hypoosmotic buffer and separation of the rhabdoms from other cell fragments by isopycnic centrifugation on Percoll. The isolated rhabdoms consist almost exclusively of the microvillar membranes of rhabdomeres R1-8 and material of the intraommatidial matrix which adheres to them. When rhabdoms are suspended in a low-Ca buffer they lose their association with the matrix material. Subsequent extraction of the isolated rhabdoms with 2% digitonin solubilizes the microvillar membranes but not the intraommatidial matrix. Spectrophotometry of such extracts reveals an absorbance peak at 486 nm and a smaller peak at about 340 nm. Both peaks are probably due to the visual pigment of retinula cells 1-6. There was no evidence of a sensitizing pigment which absorbed UV light. Irradiation of isolated rhabdoms or visual pigment extracts with blue light established the same photoequilibrium between rhodopsin and acid metarhodopsin (.lambda.max 566 nm) in each case. This indicates that the spectral characteristics of isolated rhabdoms are determined primarily by the absorption properties of rhodopsin and metarhodopsin. Irradiation of isolated rhabdoms or visual pigment extracts at pH > 7 led to the formation of alkaline metarhodopsin (.lambda.max .apprx. 380 nm). The equilibrium between acid and alkaline metarhodopsin was shifted in favor of the formation of acid metarhodopsin in isolated rhabdoms whereas the formation of alkaline metarhodopsin was favored in extracts. Metarhodopsin formed in isolated rhabdoms was less stable than in the intact eye.


Accession: 006459573



Related references

Paulsen, R., 1984: Spectral characteristics of isolated blowfly rhabdoms. Journal of comparative physiology A: Sensory neural and behavioral physiology55(1): 47-55

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