In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The morphological changes of the endothelial cells , which become more pronounced in the later stages of the experiment , the involvement of blood vessels regardless of their diameter and the location - dependent extent of the damage indicate a direct type of damage which is preceded by a mediator - induced increase in permeability , the morphological correlate of which is the formation of gaps in the interendothelial cell connections on the venules .
### Output Text:
The morphological changes of the endothelial cells , which become more pronounced in the later stages of the experiment , the involvement of blood vessels regardless of their diameter and the location - dependent extent of the damage indicate a direct type of damage which is preceded by a mediator - induced increase in permeability , the morphological correlate of which is the formation of gaps in the interendothelial cell connections on the venules . 