Table 1.

Variables, factors and events influencing the incidence of MNCL in F344 rats.

Variable/factor/event	Effect on MNCL incidence	References
Gender	Incidence higher in male than in female controls	Haseman et al. 1985Haseman 1983Haseman et al. 1998Rao & Haseman 1993
Diet – Commercial rodent chow versus NIH-07	72% increased incidence in males fed NIH-07 diet	Rao & Haseman 1993
Diet – NIH-07 versus NTP-2000	Slight decreased incidence in males and females in NTP 2000 diet feeding studies but not in inhalation studies	Haseman et al. 2003
Diet restriction	Decreased incidence. Progression is retarded but rats live longer and eventually develop MNCL	Hursting et al. 1993Imai et al. 1990Shimokawa et al. 1993Thurman et al. 1994Turturro et al. 1994Lipman et al. 1999Stefanski et al. 1990
Corn oil gavageSafflower oil gavageTricaprylin gavage	Decreased incidence in males (up to 57% lower compared to non-gavage NIH-07 diet or water gavage); females not affected	Hursting et al. 1994Rao & Haseman 1993Haseman et al. 1985Haseman & Rao 1992NTP TR 426
Body weight at 14 weeks	Positive correlation with MNCL as adult	Turturro et al. 1994
Body weight at 12 months	Slight increased incidence in both sexes	Haseman et al. 2003
Inhalation chamber control	Increased incidence in females versus feeding study	Haseman et al. 1985, 1998, 2003
Splenectomy at 1–2 months of age	Significant decreased incidence later in life	Moloney & King 1973
Splenic toxicity	Significant decreased incidence in both sexes	Elwell et al. 1996. (Report on 13 cases with decreased incidence).
StressEpinephrine and prostaglandins		Ben-Eliyahu et al. 1999Inbar et al. 2011
Increased liver tumors	Decreased incidence	Haseman 1983Harada et al. 1990
Hypophysectomy	Decreased incidence	Ward et al. 1990Stefanski et al. 1990
Germfree versus conventional	MNCL not seen in germfree F344	Sacksteder 1976
Radiation	Decreased incidence	Hellman et al. 1982
Time trends	Increased diagnoses over time in both sexes	Rao et al. 1990Haseman & Rao 1992
Refinement of diagnostic criteria	Increased incidence in both sexes based on recognition of early stages of MNCL	Rao et al. 1990
60 Hz Magnetic field	No effect on MNCL	Morris et al. 1999Sasser et al. 1996