“Ready for masking,” Svengaard said. He nodded to the computer nurse who racked the intermediary tape into position with a smooth sureness.
“Krebs cycle?” Potter asked.
“One hundred and ten coming up,” Svengaard said.
Silence.
“Mark,” Svengaard said.
Again, Potter bent to the scope. “Begin the tape,” he said. “Two minims of sulfhydryl.”
Slowly, Potter increased amplification, chose a cell for the masking. The momentary clouding of intrusion cleared away and he searched the surrounding cells for clues that mitosis would take off on his directed tangent. It was slow… slow. He’d just begun and his hands already felt sweaty in their gloves.
“Stand by with adenosine triphosphate,” he said.
Svengaard presented the feeder tube in the micromanipulators, nodded to the vat nurse. ATP already. This was going to be a tough one.
“Begin one minim ATP,” Potter said.
Svengaard depressed the feeder key. The whirring of the computer tapes sounded overly loud.
Potter lifted his head momentarily, shook it. “Wrong cell,” he said. “We’ll try another one. Same procedure.” Again, he leaned into the scope and the rests, moved the micromanipulators, pushing amplification up a notch at a time. Slowly, he traced his way down into the cellular mass. Gently… gently… The scope itself could cause irreversible damage in here.
Ahhh, he thought, recognizing an active cell deep in the morula. Vat-stasis had produced only a relative slowing in here. The cell was the scene of intense chemical activity. He recognized doubled base pairs strung on a convoluted helix of sugar phosphate as they passed his field of vision.
His beginning anxiety had passed and he felt the old sureness with the often repeated sensation that the morula was an ocean in which he swam, that the cellular interior was his natural habitat.
“Two minims of sulfhydryl,” Potter said.
“Sulfhydryl, two minims,” Svengaard said. “Standing by with ATP.”
“ATP,” Potter said, then, “I’m going to inhibit the exchange reaction in the mitochondrial systems. Start oligomycin and azide.”
Svengaard proved his worth then by complying without hesitation. The only sign that he recognized the dangers in this procedure was a question, “Shall I have an uncoupling agent ready?”
“Stand by with arsenate in number one,” Potter said.
“Krebs cycle going down,” the computer nurse said. “Eighty-nine point four.”
“Intrusion effect,” Potter said. “Give me point six minim of azide.”
Svengaard depressed the key.
“Point four minim oligomycin,” Potter said.
“Oligomycin, point four,” Svengaard said.
Potter felt that he lived now only through his eyes on the microscope and his hands on the micromanipulators. His existence had moved into the morula, fused with it.
His eyes told him that peripheral mitosis had stopped… as it should under these ministrations. “I think we have it,” he said. He planted a marker on the scope position, shifted focus and went down into the DNA spirals, seeking the hydroxyl deformity, the flaw that would produce a faulty heart valve. Now he was the artist, the master cutter—the pilot cell determined. Now he moved to reshape the delicate chemical factory of the inner structure.
“Prepare for the cut,” he said.
Svengaard armed the meson generator. “Armed,” he said.
“Krebs cycle seventy-one,” the computer nurse said.
“First cut,” Potter said. He let off the single, aimed burst, watched the tumbling chaos that followed. The hydroxyl appendage vanished. Nucleotides reformed.
“Hemoprotein P-450,” Potter said. “Stand by to reduce it with NADH.” He waited, studying the globular proteins that formed before him, watching for biologically active molecules. Now! Instinct and training combined to tell him the precise instant “Two and a half minims of P-450,” he said.
A corner of turmoil engaged a group of polypeptide chains in the heart of the cell.
“Reduce it,” Potter said.
Svengaard touched the NADH feeder key. He couldn’t see what Potter saw, but the surgeon’s forehead lens reproduced a slightly off-parallax view of the scope field. That plus Potter’s instructions told of the slow spread of change in the cell.
“Krebs cycle fifty-eight,” the computer nurse said.
“Second cut,” Potter said.
“Armed,” Svengaard said.
Potter searched out the myxedema-latent isovalthine, found it. “Give me a tape on structure,” he said. “S-(isopropylcarboxymethyl) cystein.”
Computer tape hissed through the reels, stopped, resumed at a slow, steady pace. The isovaltine comparison image appeared in the upper right quadrant of Potter’s scope field. He compared the structures, point for point, said, “Tape off.” The comparison image vanished.
“Krebs cycle forty-seven,” the computer nurse said.
Potter took a deep, trembling breath. Another twenty-seven points and they’d be in the death range. The Durant embryo would succumb.
He swallowed, aimed off the meson burst
Isovalthine tumbled apart.
“Ready with cycloserine,” Svengaard said.
Ahhh, good old Sven, Potter thought. You don’t have to tell him every step of the way what to do.
“Comparison on D-4-aminoisoxazolidon-3,” Potter said.
The computer nurse readied the tape, said, “Comparison ready.”
The comparison image appeared in Potter’s view field. “Check,” he said. The image vanished. “One point eight minims.” He watched the interaction of the enzymic functional groups as Svengaard administered the cycloserine. The amino group showed a nice, open field of affinity. Transfer-RNA fitted readily into its niches.
“Krebs cycle thirty-eight point six,” the computer nurse said.
We’ll have to chance it, Potter thought. This embryo won’t take more adjustment.
“Reduce vat stasis to half,” he said. “Increase ATP. Give me micro-feed on ten minims of pyruvic acid.”
“Reducing stasis,” Svengaard said. And he thought, This will be close. He keyed the ATP and pyruvic acid feeders.
“Give me the Krebs cycle on the half point,” Potter said.
“Thirty-five,” the nurse said. “Thirty-four point five. Thirty-four. Thirty-three point five.” Her voice picked up speed with a shocked, breathlessness: “Thirty-three… thirty-two… thirty-one… thirty… twenty-nine…”
“Release all stasis,” Potter said. “Present the full amino spectrum with activated histidine. Start pyridoxin—four point two minims.”
Svengaard’s hands sped over the keys.
“Back-feed the protein tape,” Potter ordered. “Give it the full DNA record on computer automatic.”
Tapes hissed through the reels.
“It’s slowing,” Svengaard said.
“Twenty-two,” the computer nurse said. “Twenty-one nine… twenty-two… twenty-one nine… twenty-two one… twenty-two two… twenty-two one… twenty two two… twenty-two three… twenty-two four… twenty-two three… twenty-two four… twenty-two five… twenty-two six… twenty-two five…
Potter felt the see-saw battle through every nerve. The morula was down at the edge of the death range. It could live or it could die in the next few minutes. Or it could come out of this crippled. Such things happened. When the flaw was too gross, the vat was turned off, flushed out. But Potter felt an identification with this embryo now, He felt he couldn’t afford to lose it.
“Mutagen desensitizer,” he said.
Svengaard hesitated. The Krebs cycle was following a slow sine curve that dipped perilously into the death cycle now. He knew why Potter had made this decision, but the carcinogenic peril of it had to be weighed. He wondered if he should argue the step. The embryo hung less than four points from a deadly plunge into dissolution. Chemical mutagens administered at this point could shock it into a spurt of growth or destroy it. Even if the mutagen treatment worked, it could leave the embryo susceptible to cancer.