Genetically determined thymus enlargement in the early life in BUF/Mna rats.
BUF/Mna (B) rat is a mutated strain, having much larger thymus than WKY/ NCrj (W), ACI/NMs (A), and F344 (F) rats throughout their life-span. Rats of the latter 3 strains have normal sized thymuses, being less than 5.3 in the thymus to body weight ratio (mg/g), when they were killed at 6 weeks of age. Genetic segregation of large thymus size in the B strain at 6 weeks of age was studied by crossing B rats with W, A or F rats. All of 3 types of the F1 hybrid rats between the B strain and the other strains showed intermediate thymus ratios between those of both parental strains. In F2 rats between the B and W strains, the distribution of thymus ratios showed about 5 different peaks. These findings might indicate that two polymeric autosomal loci, thymus enlargement-1 (Ten-1) and thymus enlargement-2 (Ten-2), can enlarge the thymus size in B rats. Histometrically, whole thymus and cortex areas of the B rats were 2-5 times larger than the W rats during 6-12 weeks of age, but medulla areas were slightly different between the strains, showing that larger thymuses in B rats were mainly due to the enlarged cortex areas.
Saito
M
M
Department of Pathology, Nagoya University School of Medicine, Japan.
Amo
H
H
Murakumo
Y
Y
Kojima
A
A
Katoh
H
H
Hiromatsu
T
T
Matsuyama
M
M
D000818:Animals; D000833:Animals, Suckling; D001835:Body Weight / Q000502:physiology; D005260:Female; D008297:Male; D009929:Organ Size / Q000502:physiology; D011247:Pregnancy; D051381:Rats; D011916:Rats, Inbred F344; D011919:Rats, Inbred Strains; D011921:Rats, Inbred WKY; D013950:Thymus Gland / Q000254:growth & development; D013952:Thymus Hyperplasia / Q000235:genetics* / Q000473:pathology