. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HEMOGLOBIN POLYMERIZATION IN FISH. Figure 2. Photomicrographs of adult toadtish erythrocytes (nucle- ated, as all non-mammalian erythrocytes [9]) obtained with a Zeiss Axiophot 2 microscope in differential interference contrast mode (objec- tive: Plan Apochromat, 63, oil immersion), (a) Normal cells con- taining HbO2 with spectra like those of Fig. la. (b-d). Sickled cells under anoxic condition, each with spectra similar to those depicted in Fig. Ib. Scale burs, 10/jni. the erythrocytes, usually forming elliptical and c
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HEMOGLOBIN POLYMERIZATION IN FISH. Figure 2. Photomicrographs of adult toadtish erythrocytes (nucle- ated, as all non-mammalian erythrocytes [9]) obtained with a Zeiss Axiophot 2 microscope in differential interference contrast mode (objec- tive: Plan Apochromat, 63, oil immersion), (a) Normal cells con- taining HbO2 with spectra like those of Fig. la. (b-d). Sickled cells under anoxic condition, each with spectra similar to those depicted in Fig. Ib. Scale burs, 10/jni. the erythrocytes, usually forming elliptical and closed structures. The transverse-to-tangential dichroic ratio around the cells were nearly uniform, with R ~ These results imply a flexible fibrous aggregation of Hb in which a degree of parallelism prevails. Unlike the toadfish case, tautog Hb polymerization seems to be too feeble to distort cells into "sickles"; rather it occurs along existing cellu- lar features, such as hooplike microtubules (9). Hemoglobin gelation in the summer flounder (Para- lichthys dentatus, family Bothidae) is markedly different from that in either the toadfish or the tautog. Anoxic erythrocytes in the flounder may contain intraerythrocytic clumps without sickling. Aggregates of deoxy Hb in flounder remained isotropic and did not gel into regular structures. They exhibited no linear dichroism (R —1). To distinguish isotropic from anisotropic aggregation, we regarded a cell to be sickled only when the Soret-band's linear dichroism was at least 10% above isotropic ( R a ; see Table I). Because a linearly dichroic sample should also have anisotropic polarizability, sickle cells would be expected to exhibit linear birefringence as well. Indeed, this has been observed (10) and measured (3) for human sickle cells. We found fish erythrosomes to be also birefringent. Figure 3a illustrates how toadfish erythrosomes may "light up" between crossed polarizers in various color-
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