Abdominal-inguinal Glands Research Articles

Isolation of rat mammary epithelial cells for polyamine analysis.

Mammary epithelial cells were isolated from either abdominal-inguinal glands or mammary tumours of rats, after enzymic digestion of the tissues, and were analysed for polyamine content. Optimum conditions were developed for the isolation of cells in sufficient yield for the analysis of polyamines from 1 g of mammary gland or 0.5 g of tumour tissue. Complete recoveries of the polyamines in the tissues were achieved in the isolated epithelial cells.

Mammary gland growth in the hypophysectomized pregnant rat (38522).

Sprague-Dawley-Rolfsmeyer rats were hypophysectomized on days 11, 12 or 15 of pregnancy and sacrificed on day 20 to determine the extent of mammary development, as assessed by determination of nucleic acid content. The DNA of six abdominal-inguinal glands in the hypophysectomized groups was not significantly different from that in the sham-operated pregnant or intact pregnant control groups. All groups maintaining pregnancy had significantly higher DNA contents in mammary glands than virgin control or hypophysectomized aborted groups. In order to determine the minimal numbers of placental-fetal units required to maintain pregnancy and mammary gland growth, fetuses and placentas were removed on day 12 of pregnancy in addition to the pituitary so that only one fetus and one placenta remained in the uterus of a group of 6 rats with other groups having 2, 3, 4, 5 remaining. Pregnancy was maintained with only one placental-fetal unit, but mammary gland proliferation was significantly lower than the control group on day 20 of pregnancy. Three to five conceptuses supported mammary proliferation during the latter half of pregnancy at a level not significantly different from intact or sham-operated control groups. Removal of placental units on day 12 in rats having pituitaries intact resulted in no mammary DNA change when 1-5 units remained. Removal of pitutaries on day 12 and placental-fetal units on day 14 also resulted in no change in mammary DNA with as little as two placentas (minus all fetuses),while only one placenta remaining resulted in a significantly lower mammary DNA than in groups wtih 2 or more placentas.

Correlation Between Mammary Nucleic Acids of Rats During Immaturity and Lactation1,2

Mammary deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) were measured in three abdominal-inguinal glands, surgically removed from rats aged 21, 35, or 49 days, and compared with similar measurements of the contralateral glands at Day 16 (peak) of lactation. At Day 16 the rats were divided into subgroups, depending upon whether (successful) or not (unsuccessful) each had reared six pups of her original litter without adding foster pups between Days 3 and 16 lactation. At Days 35 and 49, but not at Day 21, the mammary tissues of successful rats contained 19 to 69% more DNA and RNA than unsuccessful rats. In general, the measurements at Days 21 or 49 in predicting each criterion measured during the peak of lactation. Measurements were usually more highly correlated in successful rats the correlation coefficients between the various nucleic acid measurements at Day 35 with measurements at the peak of lactation ranged from 0.98 to 0.34. We conclude that with refinements in technique, measurements in pubertal rats may be useful estimators of future mammary development and lactational performance.

Mammary growth and milk yield as related to litter size.

SummaryLitters of primiparous lactating rats were adjusted to contain either 6, 9, or 12 young on the day of parturition. On day 13 postpartum, each rat was isolated from her litter for 16 hrs. On day 14 postpartum, each dam was anesthetized with sodium pentobarbital and weighted. The pups were then returned to their mothers, allowed to suckle the abdominal-inguinal glands, and each dam was reweighed. The difference between the prenursing and postnursing weights of the dam was used as an index of milk yield. Deoxyribonucleic acid (DNA) of the abdominal-inguinal glands was also determined. The DNA content of the glands of rats nursing 9 or 12 young was 22 and 39% greater, respectively, than that of rats nursing 6 offspring. Milk yield by rats nursing the larger litters was also significantly greater. A significant increase in litter weight gain was evident between litters of rats nursing 6 and 12 pups. These data suggested that an increase in the suckling stimulus (larger litters) resulted in an increase i...

STRENGTH OF SUCKLING STIMULUS AND MAINTENANCE OF THE MAMMARY GLAND.

SummaryGalactophores of the right 6 mammary glands of rats were ligated on day 3 postpartum and litters were adjusted to contain either 3, 6, 9 or 12 pups. Mammary glands on left side were not ligated. Rats nursing 6 young but without galactophore ligation served as controls. Animals were sacrificed on day 14 postpartum and DNA content of both left and right abdominal–inguinal glands was determined. The posterior pair of pectoral glands was used for histological study. In galactophore-ligated rats, ligated glands were significantly smaller than contralateral non-ligated glands. DNA content of ligated glands of rats nursing 12 young was similar to that of corresponding control glands whereas DNA content of glands of rats nursing 3–9 young was less than control glands. In animals with galactophore ligation, non-ligated glands were significantly larger than corresponding glands of rats without galactophore ligation. It appears that the strength of the suckling stimulus is directly related to maintenance of t...

Influence of graded thyroxin levels on mammary gland growth

The effect of graded thyroxin (T-4) doses on mammary growth in hypothyroid-ovariectomized rats treated with 2 µg estradiol benzoate and 6 mg progesterone was determined using deoxyribonucleic acid (DNA) content of the abdominal-inguinal glands as an index of the degree of cellular proliferation. Concomitant injection of estradiol benzoate, progesterone, and 1–2 µg T-4/100 g for 19 days resulted in an increase in mammary DNA. No significant difference in DNA was evident between rats receiving estradiol benzoate, plus progesterone plu 0.5 µg T-4/100 g and those treated with only estradiol benzoate and progesterone. Pituitary lactogen concentration was 28–143% greater in animals receiving T-4 than in those injected with only estradiol and progesterone. In another experiment a single injection of 2.5 or 5.0 µg T-4/100 g into lactating rats lowered the pituitary lactogen content 33–38% when compared with a control value of 1.78 µg/mg pituitary. Pituitary lactogen of rats receiving a single injection of 10 or 20 µg T-4/100 g did not differ from the controls. Thyroxin apparently influences production and secretion of lactogenic hormone, and enhancement of mammary growth resulting from thyroxin administration may be due, in part, to increased secretion of lactogen.

Growth hormone and mammary gland lobulealveolar development.

The effect of growth hormone on mammary gland lobule-alveolar growth in the ovariectomized rat was studied using deoxyribonucleic acid (DNA) of the abdominal-inguinal glands as an index of the degree of cellular proliferation. The administration of 1 mg growth hormone in combination with 2 µg estradiol benzoate for 19 days resulted in alveolar formation and an increase in mammary DNA content above that resulting from injections of either hormone alone. The mean DNA concentration of glands of rats treated with 2 µg estradiol, 6 mg progesterone, 3 µg/100 g l-thyroxine, and 0.5, 1.0, 1.5, and 2.0 mg growth hormone was significantly greater than that of animals receiving only the estradiol, progesterone, and thyroxine. The increase in the mean DNA content was due to a shift in the range of values to a higher plane and did not result from an elevated DNA in only a few animals. It is suggested that the administration of growth hormone during the growth phase of the mammary gland may have a beneficial effect on the subsequent lactation.