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Results for “Lactation, Prolonged”

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At least 19 recordsLinked to original sources
PubMed1976

Duration of diestrous period and secretion of progestins during prolonged lactation in the rat.

The duration of the diestrous period in vaginal smears and the levels of progestins in ovarian venous blood were investigated in rats whose lactation period was prolonged by replacing pups at appropriate intervals. In prolonged lactating rats, the first diestrous period after the pospartum ovulation (21.7 +/- 0.8 days) was similar to that occurring in normal lactating rats. Subsequently proestrous or estrous vaginal smears reappeared at intervals during prolonged lactation. A total of 19 rats were studied during this period of prolonged lactation and 44 diestrous periods were observed. Forty-eight % of these periods ranged in length from 11 to 16 days (mean of 12.7). Very short diestrous periods lasting less than 3 days were observed 25% of the time. Diestrous periods lasting more than 17 days were observed only infrequently (7%). Progesterone concentration in the ovarian vein during the 2nd diestrous period reached a peak 4 days after the 1st estrus and the level was maintained until 11 days after the 1st estrus. The level of 20alpha-hydroxypregn-4-en-3-one remained fairly constant throughout the 2nd diestrous period.

Animals↗
PubMed1976

Changes in body weight, milk production, food and water consumptions and vaginal smears in rats during prolonged lactation.

Concurrent observations were made in the rat on the changes in the milk production, body and organ weight, food and water consumptions and in the ovarian function in two separate series of experiments in which the period of lactation was prolonged to 60 and 45 days, respectively, by replacing suckling pups by younger ones. In most of the variable examined, marked changes occured between day 20 and 30 of lactation, that is, at the stage correspondong to the end of the normal lactation period. Milk production rate during prolonged lactation expressed by daily gain in weight of litters decreased to 60% of the level before day 20, and was associated with a great reduction of nucleic acid contents of the mammary gland. Definite decreases in weight of the anterior pituitary and the adrenal glands were observed. The food intake remained constant from day 15 of lactation onwards, therefore, the feed efficiency for milk production declined gradually during the period of normal lactatation remaining at a low level thereafter.. After the first recurrence of vaginal estrus which also occured between day 20 and 30, the replacement of litters was followed by the appearance of estrus, whereas replacement before day 15 did not affect the ovarian function. In addtition to these changes, a depressing effect of estrus on the milk production was observed.

Adrenal Glands↗
PubMed1976

Mammary nucleic acids and pituitary prolactin secretion during prolonged lactation in mice.

Lactation was prolonged until 61 days by repeated renewal of litters every week after day 12 in primiparous C3H/He strain mice. On days 12, 19, 40, and 61 of lactation, litters were removed for 5 h and after 1 h of resuckling the synthesis of DNA and RNA in the mammary gland was estimated by the incorporation of (3H)thymidine and (14C)uridine into mammary DNA and RNA in vitro respectively. Mammary nucleic acid content and pituitary and plasma levels of prolactin were also assayed. Nulliparous mice were similarly treated on day 19 of pregnancy. The percentage gain in litter weight per week was highest between days 5 and 12 of lactation, declined until days 26-33 and became steady thereafter. Mammary DNA synthesis was extremely high on day 19 of pregnancy, decreased on day 12 of lactation to less than one-fifteenth of that on day 19 of pregnancy and increased linearly therafter. Changes in mammary DNA content were not so marked, but DNA content was high on days 12 and 19 of lactation. RNA synthesis was highest on day 19 of pregnancy, abruptly decreased on days 12 and 19 of lactation and increased again with the advance of lactation. Mammary RNA content, RNA:DNA and 14C:3H ratios increased from day 19 of pregnancy to days 12-19 of lactation and decreased on days 40 and 61. While the pituitary levels of prolactin were almost constant during lactation, they were significantly higher than those on day 19 of pregnancy. There were only slight differences in plasma prolactin levels at any stage.

Animals↗
PubMed1990

Breast-milk calcium concentrations during prolonged lactation in British and rural Gambian mothers.

Detailed investigation of breast-milk calcium concentrations during 2 years of lactation have been conducted in Cambridge, UK, and rural Gambia. Mature milk concentrations remained steady for 3 months but declined during months 4-12 by over 25% (p less than 0.001). The pattern was identical in both communities despite differences in breast-feeding practices. Calcium concentrations were not related to feed frequency or breast-milk sodium concentrations, suggesting that breast involution is not responsible for the decrease after 3 months. Breast-milk calcium concentrations were characteristic of the individual, varied twofold between mothers and were independent of maternal age, parity and milk output. Gambian breast-milk contained 19% less calcium than Cambridge milk, throughout lactation (p less than 0.001). The extent to which this reflected the lower calcium intakes of Gambian mothers is unknown. Further studies are required to determine factors regulating breast-milk calcium secretion.

Breast Feeding↗
PubMed1990

Zinc in breast milk during prolonged lactation: comparison between the UK and the Gambia.

A total of 580 breast milk samples were collected from 56 lactating women living in a rural village community in The Gambia, West Africa, and 92 samples were obtained from 57 lactating women living in Cambridge, England. Total zinc content of each sample was measured by atomic absorption spectrometry, and pooled samples of the Gambian breast milks, representing successive periods of lactation, were fractionated into fat, whey and insoluble casein fractions, to examine zinc distribution. The two sets of milks both exhibited a dramatic decline in total zinc concentrations with increasing duration of lactation, in common with previous studies. However, the UK milks unexpectedly had lower zinc contents at all stages than the Gambian milks. Milk zinc levels were not significantly related to either maternal age or parity in the Gambian women. The proportion of zinc found in the sedimentable fraction remained nearly constant with increasing duration of lactation, but the proportion found in the fat fraction increased and the proportion in the whey fraction declined. These observations are potentially relevant for estimations of milk zinc availability and the fulfillment of zinc requirements by infants, and hence for infant feeding practices.

Adolescent↗
PubMed1988

Prolonged lactational infertility in adolescent rhesus monkeys.

The present study examined the effects of first pregnancy and nursing behavior on postpartum infertility in seasonally breeding rhesus monkeys to assess whether prolonged lactational infertility observed in adolescent mothers is due to a particular pattern of nursing or to decrements in body growth rates. After a successful first pregnancy, a significant percentage of the lactating adolescent mothers (57.1%; n = 8) failed to exhibit an ovulation with normal luteal phase during the subsequent breeding season. In contrast, the remaining lactating adolescents (42.9%, n = 6) and all of the adult mothers (100%, n = 6) exhibited ovulations with a normal luteal phase. Age alone was not the critical variable, since all nonlactating adolescents exhibited ovulations with normal luteal phase parameters in the subsequent breeding season. The luteal phase abnormalities exhibited by the subset of lactating adolescent females were characterized by an inadequate luteal phase (ILP) and by significantly lower serum levels of progesterone, estradiol, and bioactive luteinizing hormone. The occurrence of these ILP ovulations was associated with more frequent nursing bouts prior to ovulation and during the subsequent luteal phase. In contrast, nursing patterns for adult females who had ovulations with normal luteal phases were more similar to those of the infertile lactating adolescents exhibiting significantly longer and more frequent nursing bouts, suggesting that fully adult females may be less sensitive to the inhibitory aspects of a suckling stimulus. Differences in luteal phase function among lactating adolescents were not related to differential rates of ponderal or skeletal growth. A still-developing neuroendocrine system may thus render a significant proportion of adolescent females more sensitive to suckling-induced suppression of gonadotropin secretion.

Animals↗
PubMed1990

Breast-milk amylase activity in English and Gambian mothers: effects of prolonged lactation, maternal parity, and individual variations.

Breast milk contains an amylase that may contribute to carbohydrate digestion in infants. The aim of our study was to determine whether mothers differ in their breast-milk amylase activity and whether the activity is maintained during prolonged lactation. This was investigated by measuring breast-milk amylase activity by hydrolysis of maltotetraose in 63 English mothers of parity 1-5 and 107 Gambian mothers of parity 1-12 who were at various stages of lactation (0.5-27 mo). Amylase was present in all samples and showed a great range of activity from 0.08 to 3.53 IU/mL. Amylase activities did not vary during a feed nor over 24 h, and each mother had a characteristic level of activity in her milk. Amylase activity was higher in the 1st trimester of lactation, and decreased by 35% (p less than 0.001) to a plateau at 6-27 mo. Gambian mothers of very high parity (parity 11-12) had 54% of the activity of primiparous mothers (p less than 0.001), after adjustment for stage of lactation. Using community data on milk volume, the estimated breast-milk amylase intake by breast-fed children was on the order of 800-1000 IU/24 h in the 1st trimester and 400 IU/24 h in the 2nd year of lactation. Individual measurements emphasized the great differences in this intake among children of the same age. Our study showed that breast milk is an important source of amylase both in developed and developing countries, but there are large variations in intake among children.

Adult↗
PubMed1979

Prolactin secretion during prolonged lactational amenorrhoea.

Basal serum prolactin levels were elevated up to 66 weeks postpartum in lactating amenorrhoeic women. The serum prolactin level in fully breast-feeding women was significantly higher than in women who were partially breast-feeding. The mean basal serum prolactin level in menstruating, lactating women was significantly higher than the mean level in women who had weaned and had normal menstrual cycles. The rise in prolactin due to suckling was seen up to 66 weeks postpartum. The marked variability and lack of reproducibility of individual suckling responses may obscure the importance of prolactin secretion in the postpartum period. Nevertheless, this study confirms that prolactin secretion is increased in women with prolonged lactational amenorrhoea.

Amenorrhea↗
PubMed1984

The response of plasma prolactin to suckling during normal and prolonged lactation in the rat.

In dams which had been kept isolated from pups for 8-10 h, the magnitude of the suckling-induced prolactin rise in the plasma was studied in relation to intensity of suckling stimulus and lactational age of the mother. At midlactation the response of prolactin evoked by suckling was enhanced as litter size increased. Suckling of 2 pups induced a greater prolactin rise in dams adjusted to 2 pups than in dams adjusted to 8 pups. Suckling of 8 pups caused a greater prolactin rise in dams which had been adjusted to an 8-pup litter, than in rats with a 2-pup litter. At late and prolonged lactation the rise of prolactin in the plasma induced by the suckling stimulus of 8 pups was significantly lower than at midlactation. Injection of perphenazine after a period of suckling induced a moderate increase of plasma prolactin in dams at midlactation, and a similar increase in dams at late lactation and at day 42 of lactation. It is concluded that in the first half of lactation the number of pups, i.e. the intensity of the suckling stimulus, is an important factor in determining the magnitude of the prolactin response to suckling. The lower response of plasma prolactin to suckling in late lactation is neither caused by a decrease in suckling stimulus from the pups nor by an increase in prolactin clearance; it is probably due to a gradual reduction in prolactin synthesizing and releasing capacity of the pituitary, brought on by a desensitization of the neural or neuroendocrine system to suckling stimuli as lactation proceeds.

Animals↗
PubMed1984

Vitamin C nutrition during prolonged lactation: optimal in infants while marginal in some mothers.

Prolonged breast-feeding is practiced by mothers in the hope of improving their infants' health and preventing diseases. In this study of the nutritional adequacy of breast-feeding, 200 mothers with healthy, full term newborns were encouraged to breast-feed exclusively. At age 6 months 116 infants and at age 9 months 36 infants remained exclusively breast-fed. The control infants were weaned early and they received vitamin C through a supplemented milk formula and solid food. The exclusively breast-fed infants were able to maintain their plasma vitamin C concentration at the same or a higher concentration than the vitamin C-supplemented controls. Their plasma concentration was about 2-fold compared with the maternal concentration. It was relatively independent of maternal nutrition and of vitamin C concentration in milk. The mother's intake of vitamin C influenced their plasma and milk concentrations. About 6% of the mothers had subnormal plasma concentrations without symptoms. The lowest concentrations occurred 2 months postpartum and during the spring. Thus, exclusively breast-fed infants are well protected against vitamin C deficiency, but marginal intake in lactating mothers is more common than assumed for a well-nourished population.

Ascorbic Acid↗