Haply,for I am black and have not those soft parts of conversation that chamberers have, or for I am declined into the value of years
How Othello refers to his wife changes. Before he became Iago's puppet, Othello was sweet, respectful, and trusting of his wife.
Act 1, Scene 2, Line 61 and 85
Keep up your bright swords, for the dew will rust them...Were it my cue to fight, I should have known it
After being poisoned by jealousy and doubt, he refers to her as a whore. This shows that Othello's opinion of Desdemona has changed.
Act 4, Scene 1, lines 187-189
Compare this to when Othello was sure of his worth and not insecure, "I am as noble as the woman I married" (act 1, scene 2, line 19-22)
Act 5, Scene 2, Lines 48-49
She was false as water.
Othello also changes in the way he conducts himself. During the beginning of the play he refused to fight against Brabantio and his men. Othello advices them to put their swords away and speak to him.
After completely changing, he goes as far as slapping Desdemona. Even Lodovico is surprised about this act. Othello is known for being respectful and being able to control his actions.
In the beginning of the play, Othello had a level of trust for everyone. Now he only believes what Iago tells him. When Emilia tells Othello that Desdemona did not cheat on him, he refuses to believe her.