WorldCom

( WCOM) was the most actively traded issue in the Instinet late session Monday, although the company ? which saw its debt further lowered into the realm of junk earlier ? was treading water after falling 9% in regular trading.

Shares of the long-distance company were unchanged at $1.45 each after S&P lowered by two notches its long-term corporate credit rating.

A couple of wireless companies were also atop the volume list but unchanged:

U.S. Unwired

(UNWR)

held steady at $2.99 while

Triton PCS

(TPC) - Get Report

was even with its 4 p.m. close at $5.59.

Elsewhere,

Vasomedical

(VASO)

gave back 16 cents to $2.68 after almost doubling in the regular session on expanded FDA approval for its chest pain therapy. The company's shares rose 82% to close at $2.84 at 4 p.m. EDT on the FDA's decision, which could expand the number of patients eligible for the treatment by up to 20%.

Other stocks falling in the late session included

Tuesday Morning

(TUES) - Get Report

, down 13.4% to $18.52;

Chattem

( CHTT), down 7.6% to $33.15 after announcing a secondary offering; and

Tellium

(TELM)

, which gave back 5 cents to $1.16 after rising 10 cents to $1.21 in the regular session.

On the upside,

Dynegy

(DYN)

was gaining 25 cents to $8.80;

ValueVision Media

(VVTV)

was up 50 cents to $19.20 after affirming sales goals; and

Neoforma

(NEOF)

was gaining 23 cents to $12.23 after saying several companies had agreed to use its e-commerce product.