FWIW, nameservers lhcns1.nlm.nih.gov (130.14.55.72) and lhcns2.nlm.nih.gov (130.14.55.128) still resolve nlm.nih.gov subdomains.
At the time I was there they had a budget to die for, and Pubmed was in the top 300 websites in the world (both are probably still true). NLM pushed so much traffic because of Pubmed that they had their own internet connection to avoid DoS'ing the commodity desktop traffic of the rest of the NIH.
PubMed is self hosted in a datacenter located within NLM on the NIH campus.
They also have their own fiber connections as you mentioned.
There is also a legit storage vault located within the building that houses non digital records. We were told that there were medical records going back thousands of years kept there; and possibly as far back as the Egyptian era.
I can't ping 130.14.55.128
The most accessible tool I would recommend is zonemaster.net, a tool developed by AFNIC and The Swedish Internet Foundation. Go to advanced and type in nlm.nih.gov as domain, and then the two nameservers listed above and their ip addresses. Run the test and it will present a status summery of the domain and its name servers. (or just use this link: https://zonemaster.net/en/result/4a7d593dce6e167b)
Alternatively you can use the tool dig command tool which is the industry standard for dns debugging and probing. Installing it on windows/mac is a bit of work, but is very easy and convenient on linux. The command here would be "dig @130.14.55.128 nlm.nih.gov". The @ sign is for saying which nameserver to use, and the last part is the domain name you are looking for.