Chapter 2081: Chapter 1790: Chronic Murder_2

Yang Ping nodded and asked, "What about the organophosphates?"

Dr. Yuan said, "We’ve checked all the items at Professor Zhou’s home and found no bottles of organophosphate reagents. In the laboratory, we’ve accounted for all the chemicals registered under his name. There are two bottles of organophosphates, both are standard samples: one bottle of Malathion and one of Dichlorvos. But both bottles are still there, sealed well, with no signs of being opened."

Yang Ping frowned, "No signs of being opened?"

"Yes, the technical team checked. The sealing membranes on the caps are intact, not opened, and there are no needle marks or anything similar."

Yang Ping was silent for a long time, then said, "Okay, I understand."

He hung up the phone and sat in the chair, lightly tapping the desktop with his fingers. Zhaxi noticed that his tapping rhythm was slow, like he was calculating a complex math problem in his brain.

"Zhaxi, what did you hear?"

Zhaxi thought for a moment and said, "The deceased’s blood cholinesterase continued to decrease, indicating long-term exposure to organophosphates. But no opened organophosphate reagents were found at home or in the laboratory. This means... the source of the organophosphates is not in these places."

Yang Ping nodded, "Go on."

Zhaxi continued, "The medical report states weight loss and low blood pressure, consistent with chronic organophosphate poisoning. But the blood cholinesterase level four months ago was 2100, which is far from a lethal level. So, he had not reached acute poisoning four months ago. Something happened in the four months since."

Yang Ping glanced at him, his eyes showing a hint of approval, "Not bad. Have you thought about where the organophosphates might be sourced from if not at home or in the lab?"

Zhaxi couldn’t answer.

Yang Ping stood up, walked to the whiteboard, and picked up a marker, writing a few lines:

Source: Professor Zhou’s long-term exposure to organophosphates, but no opened reagents at home or in the lab, where’s the source?

Pathway: Absorption through skin contact? Ingestion through the digestive tract? Inhalation through the respiratory tract?

Dosage: Cholinesterase 2100 four months ago, lethal level four months later. How much did exposure increase during these four months?

Hyperpigmentation: Symmetrical distribution at fingertips, indicating long-term, repeated local contact. What is being contacted?

He finished writing and turned around, looking at Zhaxi, "These are the questions we need to answer, one by one." 𝐟𝕣𝕖𝐞𝐰𝕖𝚋𝐧𝗼𝚟𝐞𝕝.𝗰𝐨𝐦

Zhaxi stared at the words on the whiteboard, his heartbeat accelerated. He suddenly realized that this case was far more complex than he had imagined. It wasn’t a simple poisoning case, but a mystery that needed to be unraveled layer by layer.

Yang Ping sat back in the chair, picked up the phone, "Dr. Yuan, this is Yang Ping. I need you to check a few things for me. First, did anyone perform chemical residue analysis on the deceased’s clothes, especially his coat, shirt, and pants? Yes, especially on fingertip contact areas like cuffs and pockets. Second, has the tea cup at the deceased’s home, along with that book, been tested for organophosphates? Alright, I await your results."

After hanging up, he looked at Zhaxi, "Do you know why I want to check these?"

Zhaxi thought for a moment, "To find the source and pathway of the organophosphates."

Yang Ping nodded, "Yes, and there’s another reason, I’m eliminating a possibility."

"What possibility?"

Yang Ping didn’t answer directly but asked an apparently unrelated question, "Do you know, why are the typical symptoms of organophosphate poisoning constricted pupils, drooling, sweating, muscle tremors, and pulmonary edema?"

Zhaxi thought and replied, "Because organophosphates inhibit cholinesterase, causing acetylcholine to accumulate in synaptic gaps, leading to excessive excitement of parasympathetic and motor nerves."

Yang Ping nodded, "Correct, but do you know, some organophosphate compounds don’t rely solely on cholinesterase inhibition for their toxic effects? Some organophosphates inherently have direct cytotoxicity. Additionally, some organophosphates metabolize into more toxic metabolites within the body. For example, Parathion, which metabolizes into Paraoxon, increasing toxicity tenfold."

He paused, looked at Zhaxi, "So, if you’ve only examined cholinesterase, you might miss something."

Zhaxi was shocked.

Yang Ping continued, "The deceased’s blood cholinesterase was 2100, indeed insufficient for a lethal level. But what if he was exposed to a unique organophosphate compound? One that doesn’t need to fully inhibit cholinesterase to be fatal?"

Zhaxi was agape, "You’re saying... there might be other toxins?"

Yang Ping shook his head, "I’m not sure, I’m considering all possibilities. Clinical diagnosis and solving cases are alike, you list all possibilities first and eliminate them one by one. The last one standing, no matter how unbelievable, is the answer."

He instructed Zhaxi, "Go look into the literature, check which organophosphate compounds’ toxic mechanisms aren’t solely based on cholinesterase inhibition, find out and inform me."

Zhaxi stood up, ready to leave, when Yang Ping suddenly called him, "Zhaxi."

"Remember! Don’t stay up all night."

Zhaxi nodded and turned to leave.

That afternoon, Zhaxi spent the whole afternoon researching organophosphate toxicology and some emergency literature on organophosphate poisoning treatment, and he found several key papers.

The first paper, published in 2015, discusses that some organophosphate compounds, besides inhibiting cholinesterase, also directly affect the mitochondrial respiratory chain, leading to cell energy metabolism disorders. This effect appears at low doses, even sooner than cholinesterase inhibition.