Updated from 3:42 p.m. EDT

The battle of the stent makers pulsed a little faster Thursday, as

Boston Scientific

(BSX) - Get Report

,

Medtronic

(MDT) - Get Report

and

Guidant

(GDT)

all emerged as

Big Board

volume leaders after reports of their

clinical trials for treating cardiac disease were released.

Boston Scientific shares closed up 30 cents, or 0.67%, to $45.12 on volume of 14.4 million shares. The company's shares climbed 17% since Monday after data from a study said that its Taxus coronary stents could be a boon to patients who had lesions and diabetes.

Medtronic shares also started strong, rising $2.15, or 4.63%, to close at $48.55 on volume of 12.1 million shares. The company is competing for market share with its Endeavor I stent, and trading has been heavy, although several analysts said they were disappointed with aspects of Medtronic 's recent clinical trial report.

Guidant, which faces possible delays on the release of its own drug-coated stent,

reaffirmed guidance on its second-quarter earnings and tried to quiet investor worries that any hitch in the product rollout would hurt performance. Shares fell in early trading, but closed up 44 cents, or 0.82%, to $54.05 on volume of 19.2 million shares.

Tyco

(TYC)

also jumped ahead of the pack early after announcing plans to

cut debt and improve its balance sheet.

Two weeks ago the conglomerate exceeded analysts' first-quarter earnings estimates, and is about to use "a significant portion of its cash" to reduce on- and off-balance sheet debt over the next several quarters, the company said. That will cover its corporate accounts receivable securitization programs, subsidiary debt and convertible debt securities.

Tyco also announced additional voluntary pension contributions in excess of $500 million to its U.S. and non-U.S. pension plans over the next six months, but it expects to retain a cash balance of at least $2 billion.

Shares closed up $1, or 3.34%, to $30.44 on volume of 31.1 million shares.

Siebel Systems

(SEBL)

also got off to a strong, early start, with shares on the

Nasdaq

closing up 87 cents, or 8.63%, to $10.95 on volume of 26.8 million shares.

Traders were apparently reacting to rumors that the company had recently scored

some big contract wins and could be a candidate for lucrative business in Homeland Security-related software if

Lockheed Martin

is awarded a much-anticipated government contract expected to be announced this week or next.

Rounding out Nasdaq volume leaders were

Intel

(INTC) - Get Report

,

Microsoft

(MSFT) - Get Report

,

Oracle

(ORCL) - Get Report

and

Applied Materials

(AMAT) - Get Report

.

Big Board volume leaders included

TST Recommends

Lucent

(LU)

,

Nortel

(NT)

and

Gap

(GPS) - Get Report

.

Big gainers on Thursday afternoon included small-appliance maker

Salton

(SFP)

, which saw six times its normal trading volume. Shares closed up $1.59, or 39.26%, to $5.64. Despite news on Thursday of a class-action investor lawsuit, the company managed to climb back from a precipitous drop between May 10 and May 17 that saw shares skidding 53%, to bottom out at $3.12, after Salton reported third-quarter earnings that were substantially worse than expected.

Oregon Steel

(OS)

got the lead out with the release of better-than-expected earnings in the first quarter of 54 cents a share and a second-quarter forecast of $1 to $1.20. Shares closed up $2.59, up 29.94%, to $11.24 on volume of 1.9 million shares.

Krispy Kreme

(KKD)

also climbed out of the hole a bit after

a two-week plunge that the company attributed to low-carbohydrate diets taking a bite out of the doughnut-maker's performance. Shares closed up $1.08 or 5.5% at $20.73 on volume of 4.6 million shares.

Top performers on the Nasdaq included the initial public offering of

AngioDynamics

, a maker of surgical and medical instruments, which recently surged $1.50, or 13.64%, to close at $12.50 on volume of 1.6 million shares. The company priced the IPO at $11 per share, down from an initial estimate of $12 to $14 per share.

Network Engines Revs; Troy Conquers

Network Engines

(NENG)

also spiked on news that it would introduce a product based on the Microsoft Internet Security and Acceleration (or ISA) Server 2004, which enhances security for corporate email systems. Shares motored up 20 cents, or 6.78%, to close at $3.15 on volume of 1.3 million shares.

Troy Group

(TROY)

also rose Wednesday on news of the acceptance of a buyout offer from founder Patrick Dirk, whose Dirk Inc. will acquire the maker of high-security check-printing hardware. Shares closed up 60 cents, or 22.22%, to $3.30 on volume of 893,194 shares.

Mantech International

(MANT) - Get Report

headed the Nasdaq's losers Thursday after the defense contractor revised second-quarter earnings guidance downward to 15 cents a share, well below analysts' consensus estimates of 33 cents a share. Prices plunged $8.41, or 31.09%, to close at $18.64 on volume of 6.5 million shares.

Mace Security International

(MACE)

also saw the end of a spike fueled by security fears and Wednesday's FBI terror alert. Shares closed down 69 cents, or 11.08%, at $5.54 on volume of 11.9 million shares.

PSS World Med

(PSSI)

also came up lame, after reporting second-quarter earnings of 10 cents a share on income of $6.6 million -- slightly worse than expected. Analysts expected earnings of 11cents a share. The company closed down $1.24, or 10.81%, at $10.23 on volume of 4 million shares.

On the Big Board, technology and services company

CACI International

(CAI) - Get Report

led the losers after coming under government scrutiny for its employees' possible role in the abuse of Iraqi prisoners in the notorious Abu Ghraib prison, and jeopardizing future contracts for its interrogation services.

Shares screeched down $4.94, or 11.65%, to close at $37.48 on volume of 2.6 million shares.

Veritas DGC

(VTS)

, the petroleum industry services provider, dribbled downward as shares dropped $1.95, or 9.51%, to close at $18.55 on volume of 1.6 million shares. The company released its third-quarter earnings Wednesday evening, which showed a loss of 6 cents a share for its fiscal year to date.

Delta Air Lines

(DAL) - Get Report

dove on profit taking after a Wednesday announcement that it had hired the Blackstone Group for debt restructuring, something that could involve taking it into Chapter 11 bankruptcy. Shares closed down 47 cents, or 7.01%, at $6.23 on volume of 12.4 million shares.