P(32) UPTAKE BY NUCLEI

Area of Science:

• Biochemistry
• Cell Biology
• Oncology

Background:

• Mammalian tissue nuclei isolation methods are crucial for biochemical studies.
• Understanding nuclear phosphorus uptake and distribution is key to cellular processes.

Purpose of the Study:

• To describe a method for isolating mammalian nuclei.
• To investigate the uptake and distribution of radioactive phosphorus (P-32) in normal and tumor cell nuclei.
• To correlate P-32 metabolism with cellular activity, particularly mitosis.

Main Methods:

• Isolation of nuclei from mammalian tissues.
• Measurement of radioactive phosphorus (P-32) uptake by nuclei and cytoplasm.
• Fractionation of nuclear components (nucleoprotein, lipid, acid-soluble) to analyze P-32 incorporation.
• Comparison of P-32 distribution in normal liver and tumor (lymphoma) cells.
• Assessment of P-32 distribution changes following X-ray irradiation.

Main Results:

• A method for isolating nuclei in quantity from mammalian tissues was established.
• Nuclei exhibit rapid uptake of P-32, not through exchange, with tumor nuclei showing higher accumulation than normal liver nuclei due to mitotic activity.
• 60-70% of nuclear P-32 is in nucleoproteins 1-5 days post-administration; lymphoma nuclei show 90-95% in nucleoproteins.
• Calculations suggest a new lymphoma nucleus is synthesized every 27 hours, and 7 x 10^4 tetranucleotide molecules are synthesized per second.
• X-ray irradiation (200 r.) alters P-32 distribution, increasing nuclear concentration and decreasing cytoplasmic concentration shortly after, correlating with mitosis inhibition.

Conclusions:

• Tumor cell nuclear accumulation of P-32 is linked to high mitotic rates, not unique tumor metabolism.
• Nucleoprotein synthesis is a continuous process in nuclei, regardless of mitotic activity.
• X-ray-induced changes in P-32 distribution suggest a role in disrupting cellular processes like mitosis.