THE NUCLEIC ACID CONTENT OF TISSUES AND CELLS 39 



to normal levels by the simultaneous injection of estradiol and progesterone. 

 Alfert and Bern^"^ report no change in the amount of DNA per nucleus in 

 uterine cells during the estrus cycle. Rat seminal vesicles lost relatively 

 more PNA than DNA following castration, but on treatment with testos- 

 terone the PNA and DNA contents and the PNA/DNA ratio finally ex- 

 ceeded the control values. ^^ Castration and the subsequent injection of 

 testosterone have relatively little influence on the nucleic acid content of 

 liver in male and nonpregnant female rats^^; nor has testosterone any in- 

 fluence on bone marrow composition. ^^^ 



XI. Various Pathological Conditions 



1. Pernicious or Megaloblastic Anemias 



In such cases the nucleic acid content of human bone marrow shows the 

 greatest changes from normal. ^^ Both Davidson et al.^ and Men ten and 

 Willms^*^ find the average DNA-P content per nucleus increased to about 

 twice the normal diploid amount per cell and the PNA/DNA ratio is raised 

 above the normal level. Although there is some difference of opinion about 

 the fall in DNA per cell on treatment with vitamin B12 , both groups find 

 that the PNA/DNA ratio reduced as the bone marrow picture returns to 

 normal.^' • ^^^ 



2. Nerve Section, Ischemia, and Atrophy 



Wallerian degeneration in the peripheral end of a nerve after section of 

 the sciatic nerve in cats is accompanied by increasing PNA and DNA con- 

 centrations until the sixteenth day, and an increase in the PNA/DNA ratio 

 from 0.9 to a peak value of 2.0 at 32 days when cellular proliferation is in- 

 tense."® Similar changes occur after nerve crush. After nerve section and 

 muscle atrophy, Mandel*^ reports that muscle weight falls by 60 %, PNA 

 content by 55 %, and protein by 70 %. 



Ischemia, after the ligation of the pedicle of the anterior left lobe of 

 mouse liver, caused a 75 % reduction in PNA but not in DNA concentration 

 after 24 hr.^*^ After duct ligation, mouse submaxillary glands atrophy, 

 causing a 73 % fall in PNA-P content but only a 30 % fall in DNA-P after 

 30 days.^i 



Radiation Effects 



The irradiation of rats with X-rays at a dosage of 500 r. greatly reduced 

 the concentrations of PNA and DNA in the bone marrow after 4 days; at 



186 C. Lutwak-Mann, Biochem. J. 52, 356 (1952). 

 '" M. L. Menten and M. Willms, Arch. Pathol. 54, 343 (1952). 

 ■88 M. L. Menten and M. Willms, Arch. Pathol. 54, 351 (1952). 

 '89 P. Drochmans, Experientia 3, 421 (1947). 



