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. 2020 Nov 4;128(11):117002. doi: 10.1289/EHP6652

Figure 6.

Figure 6A is a panel of six images of myelin sheaths in spinal cords of transgenic fish with promoter myelin basic protein driving EGFP expression with a CAAX motif at 5 days postfertilization. Each image has a number, from 0 to 5, on the top that labels the myelin severity being depicted. The fish were exposed to 0.09 to 0.18 nanograms of domoic acid over a range of discrete developmental periods. Figure 6B is a set of five stacked bar graphs showing the distribution of myelin phenotypes from injects that occurred during discrete developments times, namely, 1, 1.5, 2, 2.5, 3, and 4 days postfertilization. The bar graphs are flipped so that the horizontal axis shows the distribution of myelin in different color and pattern blocks between 0 and 100 percent in increments of 50 percent. The fish were exposed to 0.09 to 0.18 nanograms of domoic acid over a range of discrete developmental periods.

Myelin sheaths of zebrafish at 5 d postfertilization (dpf) following exposure to domoic acid (DomA) at different developmental days. (A) Tg(mbp:EGFP-CAAX) fish were exposed to DomA (0.09–0.18 ng) over a range of discrete developmental periods (1–4 dpf), then imaged at 5 dpf using widefield epifluorescence microscopy. Images were blindly classified into six categories based on the severity of the observed myelin phenotype. The scoring was as described in detail in Figure S2. Briefly, the classification was as follows: (0) normal phenotype, (1) myelin sheaths present but disorganized, (2) myelin with noticeable deficits, (3) myelin gaps in ventral spinal cord, (4) myelin sheaths lacking in ventral spinal cord, and (5) visible sloughed myelin. Arrows indicate the myelinated Mauthner axon that is required for short latency C-bends startle responses. (B) Stacked bar plots show the distribution of the different phenotypes. Multiple trials were combined to calculate the percentage distribution per phenotype observed. Scale bar: 50μm  Table S21 includes the number of trials represented along with the associated numbers of fish per trial. Table S22 includes the myelin phenotype classification by dose and day injected. Table S24 contains the output of the multinomial logistic regression model to assess the role of developmental day of exposure on the distribution of myelin phenotypes. Table S29 contains the output of the multinomial logistic regression model for the influence of dose on the distribution of myelin phenotypes.