Hi I am Post Grad and passed out on top of the class for my Masters Program. I am presently working as an Analyst but have substantial amount of research experience. I am looking at pursuing my PhD in Life sciences in the US. Just wanted to know whether a publication is very essential to be eligible to do PhD in the US.

I don't think so, but it would be good to check with the universities you are interested in as to their admission criteria. You might also check whether you are required to have taken any kind of exam such as the GRE or GMAT ( though perhaps those are more relevant at the masters level for admissions?).

I think it's less likely to be important for admissions, but publications are likely to increase your chance of getting funding at more competitive departments.

http://lsci.tamucc.edu/Main/Admission

no idea if this is representative, but a google search on admissions for US life sciences admission requirements produced this. Again, I am not in life sciences, so no idea how the funding within those departments is structured, but my general impression is that funding is awarded via Graduate Teaching Assistantships ( GTA) in many instances, with a decrease or zeroing out of tuition, and some salary based for the teaching.

Remember that PhDs in the US have a long taught component, unlike their counterparts in the UK. GTAs might teach undergraduate classes, perhaps they teach at the (post) graduate level ( Graduate in the US means what Postgraduate in the UK means--if you said postgraduate in the US someone might think you mean post-doctoral...) as well.

Its apples and oranges, I think, when looking at "funding" in the UK and the US, for (post) graduate programs.