Studies on the particulate components of rat mammary gland. 3. The relationship between enzyme activity and particle counts in mammary gland suspensions

Abstract

NUCLEIC ACIDS IN THE MAMMARY GLAND 161 6. The significance ofthe changes in DNA content of the mammary gland are discussed. It is suggested that the changes in DNA content of the gland at parturition indicate that a wave of cell division occurs in the gland around that time.

Ribonuclease activity in the rat mammary gland during pregnancy, lactation and mammary involution

“…There is appreciable variation between the ratio of alkaline ribonuclease to DNA-P in the virgin state and in the late lactation period, whereas the same ratio for acid ribonuclease shows a smaller variation. Indeed for acid ribonuclease there appears to be an approxiimately constant amount of enzyme per cell at the various stages of the lactation cycle studied; this pattern is very different from that given by many other enzymes so far studied over the lactation cycle where the activity per cell usually shows a dramatic increase from late pregnancy to late lactation (Greenbaum & Slater, 1957c;Glock & McLean, 1958;Slater & Planterose, 1960). It is difficult to understand the significance of this finding, but perhaps the solution lies in the fact that only total enzyme activities have been considered in this paper.…”

The Effect of Locally Administered Prolactin on the Respiratory Activity of the Mammary Gland of Rabbit at the Corresponding Stage to the Alveolar Formation

“…Further it may be considerable that enzymic activities might be inhibited by the substances contained in the retained secretion. For example, on this problem Greenbaum and Slater(1957)discussed that abrupt increase of succinic oxidase activity at parturition might be in part due to the removal of colostrum, which, generally, had a much higher content of metal ions, potent inhibitors of this enzyme, than milk secreted in active lactation. Thus, the nonremoval of secretion might also be a factor responsible for the R. Q. below unity during pregnancy.…”

“…However, further study should be awaited to clarify this problem. Greenbaum and Slater(1957)studied the correlation of succinic oxidase activity with mitochondrial fractions at various stages of lactation cycle of rat, and Williams and Turner(1956)reported that the most part of intraductally injected I 131-labeled prolactin became associated with the particulate bodies of cytoplasm, the mitochondria and microsomes. It will therefore be of interest to study further the effect of prolactin on the alveolar formation and mammary growth in this connection.…”

The Length of Pregnancy and the Level of Incorporation of [Methyl-3h]thymidine Into Mouse Mammary Gland Explants in Culture

“…The relationship is highly significant (P < 0-001). It is probable that the increase in the synthesis of DNA in vitro seen throughout pregnancy reflects cellular proliferation in vivo during this period (Kirkham & Greenbaum & Slater, 1957). At the stage of pregnancy examined (16-18 days) there appears to be a relationship between the degree of stimulation by insulin of DNA synthesis in mammary gland expiants and the non-stimulated level.…”