Ralph R. Anderson

Total and free thyroxine and triiodothyronine in blood serum of mammals.

1. Blood samples were obtained from seven species of mammals: horses, cattle, sheep, goats, pigs, guinea pigs and rats for determination of total and free thyroxine and triiodothyronine. Total thyroxine in the order listed above in ng/ml was: 15, 60, 79, 185, 53, 45 and 79. Free thyroxine in pg/ml was: 5.9, 10.0, 19.2, 32.1, 21.7, 6.7 and 51.3. 2. Total triiodothyronine in pg/ml was: 677, 1290, 979, 3170, 760, 317 and 1747. Free triiodothyronine in pg/ml was: 3.22, 4.40, 2.60, 6.74, 2.74, 2.42 and 10.88. 3. Percent free thyroxine was high in rats and low in guinea pigs, while percent free triiodothyronine was high in guinea pigs and low in goats. 4. Free thyroxine and percent free thyroxine were higher in some groups of horses, particularly stallions, than in other groups.

Effect of Litter Size Upon Milk Yield and Litter Weight Gains in Rats

Summary A study is reported concerning the influence of litter size in rats on the estimated milk yields and litter weight gains on days 14 to 20, and on the DNA of the mammary glands on day 20. On day 14 of lactation, the mean milk yield increased from 5.6 g with 2 to 16.4 g with 12 in the litter. The milk yield in most groups increased until the 18th day, then decreased on day 20. The milk available/pup on day 14 was 2.8 g for the 2-pup litters and declined gradually to 1.4 g for the 12-pup litters. The litter weight on day 14 was 68.3 g for litters of 2 and increased gradually to 287.1 g for litters of 12. The gain per pup was greatest for litters of 2 and then declined with increasing litter number. At the 20th day, the DNA for litters of 2 was 8.9 mg/100 g bw and increased gradually with increasing litter size to 13.6 mg for litters of 12. The RNA also increased with increasing litter size up to 10.

Diurnal variation of plasma and pituitary thyrotropin (TSH) of rats.

Summary The diurnal variation in TSH content of the plasma and pituitary of the female adult rat under conditions of 14 hours of light and 10 hours of darkness was determined by an immunochemical technique. The plasma TSH level rose gradually from 3 A.M. to 3 P.M., then declined; whereas the pituitary TSH was highest at 3 A.M. and then declined until 3 P.M. These data suggest that the thyroid hormones would be lowest some time prior to 3 A.M. and reach a peak some time after 3 P.M., thus stimulating maximal activity during the night.

Thyroxine and Triiodothyronine in Milk of Cows, Goats, Sheep, and Guinea Pigs

Abstract Milk was collected for the first 21 days of lactation twice daily from dairy cows and once daily from goats, sheep, and guinea pigs. Thyroxine (T4) and triiodothyronine (T3) were extracted from 100 μl of milk using acidified ethanol. T4 and T3 were reconstituted in 100 μl buffer and measured by radioimmunoassay. Concentrations (ng/ml) of T4 and T3 for milk of cows, goats, sheep, and guinea pigs, respectively, were: 0.97 and 0.94, 1.24 and 0.52, 0.99 and 0.79, and 1.41 and 0.53. T4 concentration for guinea pig milk was significantly higher than for cow and sheep milk, but not for goat milk (P < 0.05). T3 was found in higher concentration in milk of cows and sheep than in milk of goats and guinea pigs (P < 0.05). Species differences in conversion of T4 to T3 in mammary gland cells are suggested. Summations of T4 and T3 concentrations in milk indicated no differences among the four species. Regression analyses of changes in milk production, T4 and T3 concentrations, total T4 and T3 in milk per day, and ratios of T4 to T3 revealed variations in patterns. Concentrations of T4 or T3 tended to decrease as lactation progressed over 21 days. Total T3 tended to increase, and the ratio of T4 to T3 tended to decrease. Amounts of T4 and T3 available to offspring from milk were calculated to be minor sources (4 to 7%) of total requirements for maintenance of metabolic functions.

Effect of relaxin on mammary gland growth and lactation in the rat.

Summary Mammary DNA, RNA and RNA/DNA were measured in groups of 10 ovariectomized rats treated for 20 days with relaxin (R) in doses of 20 and 90 guinea pig units (GPU) alone or in combination with 1 μg estradiol benzoate (EB) or EB plus 3 mg progesterone (P). No treatment, EB only, and EB plus P served as control groups. Twenty GPU R alone significantly increased DNA over the no treatment group while 90 GPU did not increase DNA any higher. Although DNA values for the EB group were higher than no treatment and EB plus P higher than EB, R was not effective in increasing DNA in combination with either EB or EB plus P. R alone at either level did not change RNA from the no treatment group, but 90 GPU R in association with EB and both levels of R in association with EB plus P significantly reduced RNA in relation to the appropriate control groups. Relaxin acts synergistically with estrogen and progesterone to develop the mammary apparatus and at the same time to suppress lactation. Removing the inhibitory effects of relaxin at parturition may be an important prelude to lactogenesis.

Effect of Relaxin on Mammary Growth in the Hypophysectomized Rat

The ovarian peptide, relaxin, has long been known to modify the structures in the area of the birth canal of the pregnant animal in preparation for parturition (Hall, 1960; Hisaw, 1926; Hisaw et al,5 1944; Steinetz et al 1960). Since relaxin is found in abundance in the blood serum of many pregnant mammals, it seems plausible that the development of the mammary gland during gestation might be regulated in part at least by the presence of the hormone. Much work in delineating qualitative hormone requirements for mammary growth in hypophysectomized rats has been accomplished through the technique of whole mount observations (Cowie and Folley, 1947; Hamolsky and Sparrow, 1945; Kahn, Baker and Zannotti, 1965; Mixner, Lewis and Turner, 1940). In the past this technique was adapted to semiquantification by at best using some arbitrary numerical scale to assign each gland a grade for the extent of development (Kahn, Baker and Zanotti, 1965; Meites, 1965; Wrenn et al., 1966). Chemical DNA determination is an acceptable method for quantification in spite of the minor complication in measuring stromal as well as parenchymal tissue, and a qualitative picture of growth is not obtained. Therefore, it was concluded that the best approach to investigating the effect of relaxin on growth and differentiation of the mammary gland was to combine previously determined DNA measurements with whole mount observations, and to develop a better method of quantification for a more valid statistical analysis.

Mammary Gland Growth in the Hypophysectomized Pregnant Rat

Summary 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 abdominalinguinal 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 or 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 concep-tuses supported mammary proliferation during the latter half of pregnancy at a level not significantly different from intact or sham-operated control groups. Removal of pla-cental units on day 12 in rats having pitui-taries intact resulted in no mammary DNA change when 1-5 units remained. Removal of pituitaries 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 with 2 or more placentas.

Physiologic role of relaxin on mammary gland growth in rats.

Abstract The role of relaxin in stimulating growth of the mammary gland was assessed in ovariectomized and intact male rats for a period of 20 days. In addition to relaxin alone, the ovarian mammogenic hormones estradiol and progesterone were used in combination with relaxin and with each other to evaluate responses of mammae. Indices for mammary growth included wet weight, dry fat-free tissue, DNA, RNA, total protein, and collagen. Quantitative estimates of DNA and collagen represented the best indicators of parenchymal and stromal growth, respectively. Because changes in body weights were significantly different among hormonally administered groups, these were included as well. In Ovariectomized young rats, relaxin alone and in combination with estradiol and progesterone increased all indices significantly (P < 0.01). The collagenous portion of total protein was high for the group receiving relaxin alone (62%) compared with the control group (46%). Relaxin administered along with estradiol and progesterone increased collagen accumulation to 73%, compared with 54% in the estradiol + progesterone group. Relaxin did not significantly increase growth indices when administered to male rats at 10 and 20 μg/day, while 30 μg stimulated a significant increase in total protein (P < 0.05), suggesting that 30 μg of relaxin/day may be considered the basal concentration needed to induce a physiologic response in males. Relaxin induced a growth effect on mammae by synergizing with progesterone and estradiol in order to stimulate parenchymal proliferation, as noted by a DNA increase, and to increase stromal distensibility of the mammary pad by invoking accumulation of collagen and total protein in substituting for mammary adipose tissue.

Effects of Relaxin in Combination with Prolactin and Ovarian Steroids on Mammary Growth in Hypophysectomized Rats

Summary Hypophysectomized-ovariec-tomized albino rats weighing 160 g were injected daily for 19 days with 90 GPU of relaxin and/or other mammotropic hormones, including prolactin (25 IU), estra-diol benzoate (1 μg), and progesterone (3 mg). Prolactin alone or in combination did not increase body weight. Mammary wet weight was increased significantly by prolactin, progesterone, and relaxin, but not by other combinations. Relaxin was without effect on mammary wet weight, but syner-gized with prolactin and progesterone to increase mammary dry fat-free tissue. It also synergized with prolactin or prolactin and progesterone to stimulate DNA and RNA of the mammary tissue, but did not increase the ratio of RNA to DNA. It is concluded that relaxin has limited mammo-tropic action by itself, but synergizes effectively with anterior pituitary and ovarian steroid mammotropins to stimulate mammary development.

Variations in major minerals of human milk during the first 5 months of lactation

Abstract Human milk samples were obtained at intervals over the first five months of lactation from 6 women. The samples were analyzed for major minerals (Ca, Mg, K, Na, and P) using the method of Inductively Coupled Argon Plasma Spectroscopy (ICAPS). Mean concentrations of the minerals on an individual basis for Ca varied from 348.8 to 191.6 ppm, for P from 159.6 to 113.5 ppm, for K from 601.4 to 491.3 ppm, for Na from 235.8 to 129.8 ppm, and for Mg from 38.4 to 25.5 ppm. These differed significantly among individuals. Daily changes over the 5 months lactation trended downward in four of the five minerals and an exponential model (Y=Ae −bX ) was chosen to describe the reduction in concentration. The exponent revealed the change in concentration on a daily basis. For Ca, the equation was Y, Ca (ppm)=303.3 e −.00115X ; for P, it was Y=161.5 e −.00246X ; for K, it was Y=556.2 e −.000551X ; for Na, it was Y=211.5 e −.00382X ; and for Mg, it was a positive regression as follows: Y=30.75 e +.0736X . Data from the literature were calculated according to the exponential model for comparative purposes. Considerable variation was found among studies. Variability in individuals and stages of lactation should be taken into account when balancing dietary needs of the offspring.