Maternal Substances Research Articles

Evidence that maternal ventral skin substances promote suckling in infant rats

Washing a lactating rat's ventral skin with acetone, alcohol and water markedly reduces the effectiveness with which her 2-week-old infants can initiate suckling on the anesthetized mother. Control experiments with detailed thermal and behavioral measures give evidence tending to rule out lowered skin temperature, altered thermal gradients, changed tactile characteristics of abdominal fur or nipples and aversion to remaining traces of the organic solvents as responsible for the infants' failure to find and attach to nipples. The data suggest that some substance(s) on the skin of the mother's ventrum act as olfactory and/or gustatory cues for the infants' orientation and attachment to nipples.

Relationship between maternal progesterones and the delayed drug metabolism in the neonate.

The relationship between maternal progesterones and the delayed drug metabolism in the rat neonate was studied with special emphasis on maternal inhibitory substances and their role in the functional development of the endoplasmic reticulum of the neonate. Incubation of liver homogenates and microsomes obtained from fetuses removed by cesarean section 1-3 days before birth indicated the presence of enzymes involved in progesterone metabolism namely 16 alpha- and 6 beta-hydroxylases and delta 4 - 5 alpha-hydrogenase. Enzyme activities determined on liver microsomes of nonpregnant and pregnant rats indicated low 6 beta-hydroxylase activity in both groups and an increase in 5 alpha-hydrogenase in the pregnant when compared to the nonpregnant (p less than . 05 or greater) rats. Weaning 2-week-old rats resulted in an increase in progesterone 16 alpha- and 16 beta-hydroxylase and coumarin 3-hydroxylase activities; however treatment with 5 beta-pregnanediol or 5 beta-pregnanolone prevented these increases. Estradiol or testosterone did not affect these activities. It was concluded that since separation of the neonate from the mother brings about an increase in drug and progesterone hydroxylation it is possible that the low activity of drug metabolizing enzymes of the fetus and neonate is connected with reduced progesterone metabolites originated from the mother.

Metabolism of drugs in rat liver during the perinatal period

Hepatic activities for the N-demethylation of aminopyrine and UDP-glucuronyl conjugation have been determined in vitro during the perinatal period. UDPglucuronyltransferase activities measured with p-nitrophenol and bilirubin as acceptors in ultrasonicated homogenates are relatively high shortly after birth and subsequently decline to the adult level at day 10 post partum. The N-demethylating activity remains low during the first 20 days after birth. In the 20 to 30-day period the enzyme activity of either sex suddenly rises. The hepatic activities in female rats reach their adult level during this period. As far as the males are concerned, the increase of their N-demethylating activity proceeds more gradually from the 30th day to a maximum at about 60 days, resulting in a marked sex difference in N-demethylation. A change in the time of weaning did not influence drug metabolism in the developing rats. It is suggested that the lower level of oxidative N-demethylation in the new-born rat is related to the presence of hemopoietic cells and to the rate of growth of the liver, rather than to a postnatal interference by maternal substances during the nursing period.

Chapter 3 The Integrity of the Reproductive Cell Line in the Amphibia

Publisher Summary This chapter attempts to present the “current state of the art” in addressing the specifics of the determination of the germ line, the integrity of the germ line as a pure cell line and its differentiation, and the developmental significance of the passage of maternal substances into the egg during oocyte growth. It demonstrates that in the Amphibia, a clear distinction exists between a reproductive cell line and a somatic cell line. Only the germ cell line retains unbroken continuity from one generation to the next and at specific times successive somatic cell lines are originated that differentiate into the body of the individual animal. The germ cells are open to the reception of a stimulus of somatic origin. This governs the cellular differentiation of the germ cells in a sperm-forming or egg-forming direction. Even when germ cells are resident in heterotypic gonads, they continue to differentiate into functional gametes and to maintain the detailed characteristics of their species of origin.

Synthesis of Phospholipids in the FŒtus

WHETHER fœtal lipids are derived primarily from the preformed maternal substances by placental transmission, or from synthesis within the fœtus, cannot yet be answered satisfactorily. Up to now, most investigators have been concerned with the placental transmission of fatty (and other) substances, and very little has been done to explore the possibility of synthesis of these compounds by the fœtus. Nielson1 studied the permeability of the rat placenta to phospholipids with the aid of P32 and found that after the injection of the mother with inorganic phosphate, labelled with P32, radioactive phospholipids could be isolated from the fœtuses within 2 hr. after the injection. When, on the other hand, an emulsion of phospholipids labelled with P32 was injected intravenously to the mother, the appearance of radioactive phospholipids in the fœtuses was very much delayed, and even then only small amounts were found. Kielson, therefore, concluded that the placenta does not transmit phospholipids and that these substances are readily synthesized within the fœtus. In my experience, when an emulsion of phospholipids is injected intravenously, so long as any of the excess phospholipid remains in the circulation, it always stays in the form of an emulsion. The only conclusion, therefore, that can be drawn from Nielson's work is that the placenta does not transmit emulsions of phospholipids; whether this is also true for the plasma phospholipids in the physiological state of dispersion remains an open question. In order to follow the. experimental design of Nielson in the investigation of the sources of fœtal phospholipids, the mothers should be transfused with plasma containing labelled phospholipids. Up to now, the supplies of P32 in Great Britain have been small, and therefore this experiment, requiring relatively large amounts of the isotope, is not practicable.