// example xml record

<Records>
- <Record>
  <Last>TwoFrame</Last>
  <First>TwoFrame</First>
  </Record>

// how can i access nodes by name with my responseXML object?

var xmldoc = req.responseXML;
var results = xmldoc.getElementsByTagName('Record')[0];
alert(results[5].childNodes[0].nodeValue);