Hormones in milk

Isolation and detection of microRNA from the egg of chickens

Background

The egg is a vital part of the chicken developmental process and an important protein source for humans. Despite the chicken egg being a subject of intense research little attention has been given to the role of microRNAs within the egg.

Findings

We report a method for the reproducible and reliable isolation of miRNA from the albumen and yolk of chicken eggs. We also report the detection via real-time PCR of a number of miRNAs from both of these biological fluids.

Conclusions

These findings provide an interesting look into the chicken egg and raise questions as to the role that miRNAs maybe playing in the chicken egg. This method of detecting miRNAs in chicken eggs will allow researchers to investigate the presence of an additional level of epigenetic programming in chick development previously unknown and also how this impacts the nutritional value of eggs for human consumption.

The epidemiology of acne vulgaris in late adolescence

Importance

Acne vulgaris is the most common skin condition affecting late adolescents across the globe. Although prior studies have evaluated epidemiologic patterns of acne vulgaris in various ethnicities and regions, adequate understanding of the worldwide burden of the disease associated with patients in their late adolescence (15–19-year olds) remains lacking.

Objective

To assess the global burden of the disease associated with acne vulgaris for late adolescents (15–19-year olds) and provide an overview of the epidemiology, pathophysiology, and treatment options for acne in this population.

Design

Database summary study.

Setting

Global Burden of Disease Study 2010 database.

Participants

Global Burden of Disease regions comprised countries with prevalence of acne vulgaris between the ages of 15 and 19 years.

Main outcomes and measures

Geographic region-level disability-adjusted life year rates (per 100,000 persons) associated with acne vulgaris in years 1990 through 2010. Median percentage change in disability-adjusted life year rates was estimated for each region across the specified study period.

Conclusion and relevance

Acne vulgaris-associated disease burden exhibits global distribution and has continued to grow in prevalence over time within this population. This continued growth suggests an unmet dermatologic need worldwide for this disorder and potential opportunities for improved access and delivery of dermatologic care. Our analysis of the literature reveals numerous opportunities for enhanced patient care. To that end, we highlight some of the effective and promising treatments currently available and address important factors, such as sex, nationality, genetics, pathophysiology, and diet, as they relate to acne vulgaris in late adolescence.

Role of sensory, social, and hormonal signals from the mother on the development of offspring

For mammals, sensory, social, and hormonal experience early in life is essential for the continuity of the infant's development. These experiences come from the mother through maternal care, and have enduring effects on the physiology and behavior of the adult organism. Disturbing the mother-offspring interaction by maternal deprivation (neglect) or exposure to adverse events as chronic stress, maltreatment, or sexual abuse has negative effects on the mental, psychological, physiological, and behavioral health. Indeed, these kinds of negative experiences can be the source of some neuropsychiatric diseases as depression, anxiety, impulsive aggression, and antisocial behavior. The purpose of this chapter is to review the most relevant evidence that supports the participation of cues from the mother and/or littermates during the postnatal preweaning period for the development of nervous system of the offspring. These findings come from the most frequently utilized experimental paradigms used in animal models, such as natural variations in maternal behavior, handling, partial maternal deprivation, and total maternal deprivation and artificial rearing. Through the use of these experimental procedures, it is possible to positively (handling paradigm), or negatively (maternal deprivation paradigms), affect the offspring's development. Finally, this chapter reviews the importance of the hormones that pups ingest through the maternal milk during early lactation on the development of several physiological systems, including the immune, endocrine systems, as well as on the adult behavior of the offspring.

Wistar-Kyoto and spontaneously hypertensive rat blood pressure after embryo transfer into different wombs and cross-suckling

Blood pressure (BP) varies based on genetic and environmental factors. To test genetic and environmental influences on body weight (BW) and BP, one-cell homozygous embryos were transferred into spontaneously hypertensive (SHR, pup:shr) or (Wistar-Kyoto normotensive [WKY], pup:wky) normotensive rats' oviducts (embryos: s,w; oviduct-uterine: S,W), cross-suckled at birth (nurses S,W) and weaned to normal diets at day-21. BP at day-120 was measured by radiotelemetry and analyzed by methods of linear least square rhythmometry and analysis of variance. Genetics dominantly affected shr BP, causing it to be significantly higher at birth (24.6 ± 1.8 in sS versus 21.8 ± 1.7 mmHg in wW, P < 0.005), and at day-120 (198 ± 0.5 in sSS versus 127 ± 0.2 mmHg in wWW, P < 0.001), with lower BW than those of wky (5.3 ± 0.2 versus 5.7 ± 0.2 g at birth, 332 ± 5 versus 404 ± 6 g at day-120, both P < 0.001). Surprisingly, uterine-suckling milieus lowered shr BP significantly at day-120 (198 ± 0.5 in sSS versus 178 ± 0.5, 147 ± 0.6, 179 ± 0.5 mmHg in sSW, sWS, sWW, respectively, all P < 0.01). BP was slightly elevated when wky-genetics were implanted into the S-uterine by 4 mmHg (wSW, P < 0.05), whereas implanting shr embryos into the W-uterine environment (sWS) lowered BP by 51 mmHg (P < 0.001). In summary, the hypertensive shr-strain showed significantly lower BP when provided with an WKY-uterine environment and/or by WKY-nursing mothers, indicating that environment can modify genetic influences; yet the shr MESORs (rhythm-adjusted 24-h mean: midline estimating statistic of rhythm) lowered by WKY environments remained above MESORs encountered in wky-donors.

Regulation of prolactin transformation in the rat pituitary

We have investigated the mechanisms involved in the inhibition by dopamine of the transformation of prolactin within the anterior pituitary of the lactating rat. The degree of inhibition depends on the intracellular age of prolactin, being greater in newly synthesized (<1 hour) and in older (>12 hours since biosynthesis) hormone and lesser in prolactin synthesized 4-8 hours earlier. Transformation occurs in prolactin granules and involves an increase in oligomeric forms of prolactin at the expense of the monomeric form. A reversible disulphide-linked mechanism may be involved in dopamine inhibition of prolactin transformation; it is dependent upon the intracellular and/or intragranular pH via a Na+/H+ exchange mechanism. Transient suppression of dopamine inhibition may lower the intracellular/intragranular pH and subsequently cause transformation of the hormone. Developmentally, dopamine secretion by tuberoinfundibular neurons is seriously impaired and the response of pituitary lactotrophs to dopamine is reduced in adult rats deprived of milk prolactin during Days 2-5 post partum. These results suggest milk prolactin ingested during a critical post partum period may exert an organizational effect upon dopamine secretion and its function on the pituitary lactotroph during adulthood.

Gastrointestinal tract as a target organ for orally administered insulin

The intestine is not considered to be a classic target tissue for insulin. Recent in vitro and in vivo experiments suggest that intestinal as well as systemic effects are observed following oral administration of insulin. Local effects include enhancement of intestinal growth, cell maturation, enzyme expression, gut adaptation after intestinal resection and reduction of intestinal permeability. Systemic effects, at least in animal models, include favorable effects on blood glucose and lipid profile and on the prevention of autoimmunity and attenuating the atherosclerotic process.

Expression of porcine epidermal growth factor in Pichia pastoris and its biology activity in early-weaned piglets

Early-weaned piglets often have abnormalities in intestinal morphology and function. Epidermal growth factor (EGF) is critical in the development and in the repair of the gastrointestinal tract in pigs. This study investigated the effects of dietary EGF supplementation on growth performance and small intestinal morphology of early-weaned piglets. The functional domain of porcine EGF (pEGF) was cloned after RT-PCR amplification. The recombinant protein was expression by the Pichia pastoris expression system and the construct pPIC9K-pEGF was transformed into host GS115. The secretary recombinant protein in the supernatants was analyzed by SDS-PAGE. The gel indicated that the extra band at 6 kDa in the transformant, which corresponds to the standard hEGF, were both reactive to anti-pEGF antibody by Western blotting. The expression level of pEGF in the culture supernatant was 870 microg/mL. An animal feeding test was conducted to identify the effects of pEGF supplementation on growth performance and the development of digestive tracts of 14-day weaned piglets. The dietary treatment was a corn-soybean meal basal diet either with or without 1.5 mg/kg recombinant pEGF from the transformant fermentative supernatant. Dietary treatments enhanced the daily gain during 0-7 days postweaning (p < 0.05), but did not affect the performance throughout the entire test period. Dietary supplemental pEGF significantly increased serum IgA levels on day 18 postweaning, and increased the mucosa IgA levels and crypt depth at jejunum on day 28 postweaning (p < 0.05). The experimental results showed that the recombinant pEGF could be secreted by P. pastoris. The trophic effects of pEGF on growth performance, immune response, and small intestine development were determined by feeding recombinant pEGF to early-weaned piglets.

Repetitive exposures to a surrogate nipple providing nutritive and non-nutritive fluids: effects on suckling behavior of the newborn rat

Responsiveness to a surrogate nipple providing water, 0.1% saccharin, 10% sucrose, pedialyte, or milk was tested in naïve-to-suckling newborn rats during six 10-min exposures, one every 1.5 h over a 7.5 h period. Across a succession of exposures, newborn rats repeatedly attached to and ingested milk from a surrogate nipple, yielding significant body weight gain and increased concentration of blood plasma glucose. Initially, pups ingested considerable amounts of saccharin and sucrose, but then dramatically decreased their consumption of these fluids across the experimental sessions. Intake of milk was significantly higher than that of all other substances. Blood glucose concentration in pups treated with water, saccharin, sucrose, and pedialyte did not differ significantly from that of non-treated pups. The present data suggest a potential contribution of a fluid's palatability and nutritive value in the persistence and efficacy of diet intake for neonatal rats in the context of suckling behavior.

Concentrations of triiodothyronine (T3), tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in milk from healthy and naturally infected quarters of cows

The effect of naturally acquired bacterial infection of the bovine udder on the activity of 5'-thyroxine monodeiodinase (5'-MD), and on the concentrations of the pro-inflammatory cytokines interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha in milk, from healthy (control) and inflamed quarters, was determined. The diagnostic procedure included history and clinical examination of the udder, macroscopic evaluation of secretions, the Californian Mastitis Test, determination of somatic cell counts and bacteriological examination of milk. It has been found that the milk triiodothyronine (T3) content and the 5'-MD activity from inflamed quarters were decreased when compared with controls. The decrease in the milk T3 from subclinical mastitic quarters was manifested when somatic cell counts were > 10(6) ml(-1). TNF-alpha was on average 2-fold higher in infected milk, and the concentration of IL-6 was unchanged. These results suggest that the decreased T3 content in mammary secretions during naturally occurring mastitis is associated with the severity of inflammation, increased TNF-alpha concentration and impaired enzymatic activity of 5'-MD.

Labor pain effects on colostral milk beta-endorphin concentrations of lactating mothers

beta-Endorphin (beta-EP) levels of colostral milk are approximately two-fold higher than in plasma of lactating women, in who concentrations peak at term, after the first and second stages of labor. We investigated the effect of labor pain and vaginal parturition on colostral beta-EP concentrations (beta-endorphin (125)I RIA, Incstar Corp., Stillwater, Minn., USA) of at-term nursing mother, in comparison to those having undergone elective cesarean section. Our results show that colostral milk beta-EP concentrations of mothers who delivered vaginally are significantly higher on the 4th postpartum day (6.0 +/- 0.5 vs. 4.3 +/- 0.4 pmol/l, respectively; p < 0.01) than colostral levels of mothers who underwent cesarean section. These data indicate the important influence of the labor process on the colostral opioid galactopoiesis. It is suggested that labor and parturition pain may increase colostral milk beta-EP concentrations of lactating mothers in order to help the newborn overcome the stressful perinatal events of natural labor and delivery.

Motilin in human milk: identification and stability during digestion

The presence of motilin in human milk and the influence of human milk on the degradation of [125I][Nle13] porcine motilin by gastric and duodenal fluids were investigated. Milk and plasma samples were collected from 14 mothers, and motilin was measured by radioimmunoassay. Plasma levels were 416 +/- 37 pg/mL. In 8 defatted samples the motilin level was 105 +/- 14 pg/mL, in the six others levels were above 1000 pg/mL but dilution curves were non-linear. After solid-phase extraction milk levels were 108 +/- 21 pg/mL in 13 samples, in 1 sample the dilution curve was still non-linear. The stability of motilin after ingestion was studied in vitro by incubating [121I][Nle13] porcine motilin with gastric and intestinal juices obtained from newborns (10 times diluted). Incubations were performed at 37 degrees C at pH 1.8, 3.2 and 5.8 for the gastric fluid and at pH 7.4 for the duodenal fluid. After different times of intervals (5, 10, 20 and 30 minutes) intact motilin was precipitated with trichloroacetic acid and the radioactivity of the supernatant was determined. Motilin was rapidly degraded by gastric juice. The breakdown was greatest at pH 3.2 (74% after 30 minutes) and lowest at pH 5.8 (29%), the pH after milk feeding in neonates. Degradation by intestinal juice at pH 7.4 was also very rapid (77% after 30 minutes). Human milk and BSA inhibited partially the gastric digestion at pH 3.2 (17 and 29%, respectively). Digestion by intestinal juice was not affected by human milk and BSA. These results suggest that digestion of motilin in the stomach may be sufficiently retarded by human milk in the newborn to exert a biological role.

The effect of recombinant TGFalpha, human milk, and human milk macrophage media on gut epithelial proliferation is decreased in the presence of a neutralizing TGFalpha antibody

OBJECTIVE

An in vitro model was devised to compare the relative effects of recombinant transforming growth factor-alpha (TGFalpha), aqueous human milk, and human milk macrophage (HMM) medium on human fetal small intestinal cell (FHs-74) proliferation.

METHODS

Recombinant TGFalpha at increasing concentrations (range 0.01-1,000 ng/ml media), the aqueous fraction of human milk (AHM), or HMM medium was added to FHs-74 cells in the presence or absence of a neutralizing TGFalpha antibody (1 microgram/ml medium). At 24 h, cell proliferation was measured and expressed as percent control. The experimental variables were (1) activators of cell growth (TGFalpha, AHM, and HMM medium); (2) increasing concentrations of TGFalpha, and (3) neutralizing antibody to TGFalpha. The dependent variable for all experiments was cell proliferation.

RESULTS

Significant effects for growth stimulators and TGFalpha concentration as measured by cell proliferation were found. Specifically, there was a dose-dependent effect of TGFalpha on cell proliferation to the 5-ng/ml concentration, with a plateau reached in cell proliferation at higher concentrations. The stimulatory effect of TGFalpha was decreased in the presence of TGFalpha antibody (mean +/- SD 22 +/- 7. 1% decline, p < 0.001). In the presence of TGFalpha antibody, there was a 25 +/- 3.1% decline in HM-stimulated growth (p < 0.004), and a 27.6 +/- 3.2% decline in HMM medium-stimulated growth (p < 0.001).

CONCLUSIONS

Neutralization of recombinant TGFalpha and that present in human milk and HMM medium by TGFalpha antibody led to a consistent decrease in in vitro human fetal small intestine epithelial proliferation without affecting cell viability. These results support the hypothesis that TGFalpha, whether derived from human recombinant sources, human milk or HMM medium has a measurable, trophic effect on in vitro human gut epithelial cells.

LHRH and somatostatin effects on the cell proliferation of the gastric epithelium of suckling and weaning rats

The aim of this study was to investigate the effects of LHRH and somatostatin on the cell proliferation of the gastric epithelium of suckling and weaning rats after fasting treatment. Previous studies on the cell proliferation of the gastric epithelium have shown that fasting stimulates this process in suckling, but not in weaning and adult rats. As milk is the most important source of nutrients and hormones during the suckling phase, and luteinizing hormone-releasing hormone (LHRH) and somatostatin are found in milk, their possible inhibitory roles on the gastric epithelium were investigated. Metaphasic index was achieved by vincristine blockade in 18- and 22-day-old treated and non-treated rats. The results showed that at 18 days, both hormones inhibited the enhanced proliferation activity due to fasting treatment, while at 22 days, no effect was detected. Therefore, LHRH and somatostatin were considered to have inhibitory roles on the cell proliferation of the gastric epithelium in suckling rats only.

Special properties of human milk

In this review, several nutritional and nonnutritive differences between mothers' milk and formula and their relationship to neonatal gastrointestinal and immune processes are discussed. The dynamic relationship of human milk as evidenced by its changing composition, unique bioactive and immunologic properties, and specialized cellular components is further delineated. The clinical significance and relevance of these findings to the clinician are then presented. Lastly, educational strategies, their effectiveness in promoting breastfeeding, and an approach that might be taken by the clinician to encourage breastfeeding are outlined.

Milk electrolyte content of Dahl hypertensive and normotensive rats

Milk samples were collected from lightly anesthetized lactating female rats of the Dahl hypertension-sensitive (SS/Jr) and Dahl hypertension-resistent (SR/Jr) inbred strains on postnatal days 8, 14 and 18. These milk samples were stored at 4 degrees C until analyzed for content of calcium (Ca++), magnesium (Mg++), chloride (Cl-), potassium (K+), sodium (Na+), and total protein. Our findings revealed that milk samples from females of the two strains were remarkably similar in content of electrolytes and total protein at each of the three sampling times. The only significant difference from among a total of 18 strain comparisons across the three sample times was that milk levels of Ca++ were significantly higher in SS/Jrs compared to SR/Jrs on postnatal day 14. These findings clearly indicate that these milk constituents do not differ between mothers of the two Dahl strains. Thus, milk concentrations of electrolytes and protein do not appear to serve as an environmental stimulus during the preweanling period for the dramatic age-related increases in arterial pressure characteristic of the SS/Jr strain.

Thyroid-induced changes in the growth of the liver, kidney, and diaphragm of neonatal rats

Eu-, hypo- and hyper-thyroid rats were studied 12 days postpartum. Hypothyroidism was induced by administering propylthiouracil (PTU) via the mother's drinking water between late gestation and throughout lactation. This procedure effectively blocked the normal early postnatal surge of T3 and T4. In contrast, hyperthyroidism was induced in the young pups by daily injections of T4 from day 3 postpartum. The effects of these experimental manipulations of thyroid status on the rates of protein turnover and growth of the liver, kidney, and diaphragm were studied and compared with measurements made on appropriate euthyroid control tissues. Tissue rates of protein synthesis were decreased in response to hypothyroidism with consequent growth retardation of all three tissues and the whole animal. In contrast, the three body tissues responded very differently to the induction of hyperthyroidism. Hepatic rates of protein synthesis and growth were completely unaffected by thyroid excess. The response of the diaphragm was essentially the reverse of that seen with hypothyroidism, i.e., the enhanced rates of protein synthesis and protein degradation leading to muscle hypertrophy. The rates of protein turnover in the kidney were also increased, but unlike the diaphragm the net result was renal atrophy. Clearly, thyroid hormones influence the normal rapid growth of the neonate and its individual tissues. However, beyond a certain concentration the threshold of responsiveness to these hormones seems to vary between individual tissues.

Timing of preweanling maternal effects on development of hypertension in SHR rats

Cross-fostering of litters was used to determine the timing of preweanling maternal influences on the development of high blood pressure in spontaneously hypertensive (SHR) rats. The SHR litters were either reared by their natural mothers or reciprocally cross-fostered to normotensive Wistar-Kyoto (WKY) mothers for postnatal days 1-7, 1-14, 1-21, 8-21, or 15-21. All SHR litters were weaned at 21 days of age and males were housed in groups of two to three per cage until physiological measures were obtained at 100 days of age. At 100 days of age, all rats were surgically prepared with tail artery catheters and, on the day after surgery, direct measures of mean arterial pressure (MAP, mmHg) and heart rate (HR, bpm) were obtained while rats were resting and undisturbed in their individual home cages. Our findings indicate that cross-fostering SHR pups to WKY foster mothers was attended by significant effects on body weights at weaning and on adult MAPs. Compared to control SHRs, cross-fostered SHRs, with the exception of the 15-21-day group, were significantly heavier at weaning. By 100 days of age, body weights of SHRs were similar across treatment groups. Basal MAPs of SHRs cross-fostered for days 1-7, 1-14, 1-21, and 8-21, but not days 15-21, were reduced significantly compared to SHR controls reared by their natural mothers. In contrast, basal HRs were not affected in any of the cross-fostered SHR groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Anomalous adrenalectomy-induced Fos-like immunoreactivity in the hypothalamic paraventricular nucleus of stress-hyporesponsive rats

Cellular activity in the paraventricular nucleus of the hypothalamus (PVN) in response to adrenalectomy (ADX) and sham-ADX was measured in adult male rats, lactating females, and nursing pups using c-fos immunocytochemistry. Increased Fos-like immunoreactivity (FLI) was seen in the PVN of male rats at 4 h following ADX or sham-ADX but this increase was transient, and basal values were restored within 24 h. In suckling pups, ADX induced a marked FLI response in the PVN at 3 days and at 18 days postpartum. At 11 days postpartum, however, the FLI response was attenuated relative to adult animals, and 3- and 18-day-old pups. Similarly, in nursing mothers, ADX induced FLI at 3 days, but this response disappeared by 7 days and did not reappear by the end of the suckling period (day 21). These data indicate that c-fos expression is a sensitive indicator of hyporesponsiveness in the hypothalamic-pituitary-adrenal (HPA) system.

Secretion of insulin-like growth factor II into milk

125I-labeled insulin-like growth factor II (IGF-II) was infused directly into the pudic artery supplying one gland of lactating goats (n = 4). Maximum specific activity for [125I]IGF-II transferred into milk from the infused gland was reached 60 min after that in plasma and was 2.5 fold greater than in milk from the non-infused gland. Inclusion of either 67.5 nmoles unlabeled IGF-II or IGF-I had no influence on the amount or pattern of secretion of [125I]IGF-II into milk from either gland. While the temporal pattern of secretion of [125I]IGF-II into milk was consistent with a transcellular mechanism of transfer, the lack of competition by unlabeled IGF-II or IGF-I suggests a non-specific mechanism is operable, which contrasts to secretion of IGF-I.

Lack of effects of neutralization of parathyroid hormone-related protein on calcium homeostasis in neonatal mice

Large quantities of parathyroid hormone-related protein (PTHrP) are present in the milk of various species. It has been suggested that PTHrP may play a role in neonatal calcium homeostasis. In the present study we evaluated the effect of neutralization of amino-terminal PTHrP activity by passive immunization in 1-day-old mouse pups. Neutralization of amino-terminal PTHrP activity had no significant effect on serum calcium or whole-body calcium content in the neonatal mice. In additional studies, we demonstrated that subcutaneous administration of PTHrP-(1-34) increased serum calcium, whereas oral administration had no significant effect in 3-day-old pups. The studies therefore demonstrate that the amino terminus of PTHrP may not play a significant role in neonatal calcium homeostasis. Local effects of PTHrP cannot be excluded by the results of the present study.

Changes in cortisol and thyroid hormone concentrations during early development and metamorphosis in the Japanese flounder, Paralichthys olivaceus

Both cortisol and thyroid hormones were detected in newly fertilized eggs of the Japanese flounder, Paralichthys olivaceus. Mean cortisol levels ranged around 2.5 ng/g wet weight. Cortisol concentrations declined to about one-tenth of their initial levels by 2 days before hatching. The concentrations of triiodothyronine (T3; 7 ng/g) were greater than those of thyroxine (T4; 0.4 ng/g). The T3 levels decreased gradually in the eggs until the time of hatching and then decreased rapidly to undetectable levels within 2 days, whereas T4 remained at more or less constant levels during early development. The significance of the "selective" clearance of the three hormones from eggs remains unclear. Tissue concentrations of cortisol during premetamorphosis were about 4 ng/g and increased to a peak level of 11 ng/g at climax. After climax, cortisol declined by 50%. The changes in thyroid hormone levels were in parallel with the changes in cortisol. T4 remained below 1 ng/g during prematamorphosis but increased gradually during prometamorphosis, reaching peak levels (12 ng/g) during metamorphic climax, and then declined by approximately 50%. T3 remained at low levels through most of the metamorphosis. Histologically, the interrenal tissue was activated during the metamorphosis. The coincident increases in cortisol and thyroid hormones support previous results of a synergistic action of both hormones during metamorphosis in the flounder.

Effect of lactation on the decline of brush border lactase activity in neonatal pigs

It has been shown that during the early phase of lactation porcine milk contains high concentrations of hormones and growth factors. The aim of the present investigation was to examine the hypothesis that the temporal coordination of intestinal maturation in piglets can be extrinsically regulated through changes in the composition of milk during the suckling period. Gut morphology and the ontogeny of brush border lactase activity were investigated in piglets reared on two suckling regimens designed to expose the animals to compositionally distinct milk. The first group of animals were cross-fostered onto postcolostrum sows and thereafter suckled normally for up to eight weeks. These normally suckled (N) animals consequently received both early and late lactation products. The second group of piglets were cross-fostered each week, for up to eight weeks, onto newly farrowed sows which were postcolostrum. As a result of this repeated cross-fostering (CF) these animals received only early lactation products. Animals were sacrificed at one, three, five, seven, and eight weeks postpartum. Biochemically active lactase decreased significantly (p less than 0.001) in both groups over eight weeks, but the rate of loss of activity was greater in the CF animals than in the N pigs by approximately 50% at week 3 and 25% at week 8. Quantitative histochemical analysis of lactase activity corroborated the biochemical data. At three weeks maximal enzyme activity was observed approximately 400 microns from the villus/crypt junction. Histochemically detected lactase decreased throughout the suckling period, but the intensity of reaction product was consistently weaker over the entire villus surface in the CF animals. Immunocytochemically detectable lactase was identified at the same sites as the histochemical reaction products. In addition, immunofluorescence microscopy showed the presence of histochemically undetectable enzyme on the basolateral and brush border membranes of both villus and crypt cells. Villus/crypt ratios were significantly lower (p<0.001) in the CF animals than in the N pigs between weeks 3 and 5. The results of this study suggest that lactation products can accelerate the loss of brush border lactase activity. The observed decline in biochemically and histochemically detected lactase was considered to be a consequence of reduced enterocyte lifespan, decreased synthesis of enzyme protein, or altered post-translational modification of enzyme protein, or a combination of there.

Transforming growth factor (TGF)-alpha in human milk

Transforming growth factor (TGF)-alpha and epidermal growth factor (EGF) were measured in human milk by means of homologous radioimmunoassay. As previously reported, EGF concentration in the colostrum was approximately 200 ng/ml and decreased to 50 ng/ml by day 7 postpartum. The value of immunoreactive (IR)-TGF-alpha was 2.2-7.2 ng/ml, much lower than that of EGF. In contrast to EGF, the concentration of IR-TGF-alpha was fairly stable during the 7 postpartum days. There was no relationship between the concentrations of IR-TGF-alpha and IR-EGF, suggesting that the regulatory mechanism in the release of the two growth factors is different. On gel-chromatography using a Sephadex G-50 column, IR-EGF appeared in the fraction corresponding to that of authentic human EGF, while 70%-80% of the IR-TGF-alpha was eluted as a species with a molecular weight greater than that of authentic human TGF-alpha. Although the physiological role of TGF-alpha in milk is not known, it is possible that it is involved in the development of the mammary gland and/or the growth of newborn infants.

Neuroendocrine peptides in milk

Milk, which is a mammal-specific biologic fluid, contains several neuroendocrine peptides at concentrations higher than those found in plasma. These neuroendocrine peptides can be synthesized or processed in the mammary gland or excreted into milk through various pathways. In addition, certain milk proteins, notably casein, can be enzymatically processed to release "exorphins," peptides with opioid activities. In suckling mammals, hormones and neuropeptides are absorbed through the gastrointestinal tract and appear intact in the plasma. This absorption is age dependent and could have physiologic significance in neonatal development.

Presence of immunoreactive endothelin in human milk

Endothelin-like immunoreactivity was detected in human milk at a concentration of 6.8 +/- 1.6 pmol/l (mean +/- SEM; n = 16) using a highly sensitive radioimmunoassay. Gel filtration and fast protein liquid chromatography (FPLC) verified the identity of the endothelin. FPLC revealed 4 peaks, one eluting just after the void volume, and the other three in the positions of endothelin-1, -2, and -3, respectively.

Beta-endorphin-like and alpha-MSH-like immunoreactivities in human milk

We measured with radioimmunoassay the beta-endorphin-like and alpha-MSH-like immunoreactivities in milk and plasma of 8 lactating women. Mean beta-endorphin concentrations ( +/- SD) were 16.6 +/- 6.7 fmol/ml in milk and 9.9 +/- 4.1 fmol/ml in plasma. alpha-MSH concentrations (mean +/- SD) were 39.4 +/- 15.5 pg/ml in milk and 18.2 +/- 8.4 pg/ml in plasma. The concentrations of both peptides in milk were significantly (p less than 0.05) higher than in plasma. No significant correlation between milk and plasma concentrations of these peptides was found.

Relaxin in paired samples of serum and milk from women after term and preterm delivery

In a study to determine if relaxin could be measured in milk and if so to correlate concentrations in milk and serum, paired samples of milk and serum were collected from 12 women 3 days after term delivery (term group), from 16 women 3 days after preterm delivery (preterm group), and from some of these patients 6 weeks after delivery (eight term and six preterm). Relaxin was measured by specific human relaxin radioimmunoassay. Relaxin from milk and sera behaved similarly in the relaxin radioimmunoassay and reverse-phase high-performance liquid chromatography. Concentrations of relaxin in sera and milk collected 3 days after delivery did not differ significantly within the term or preterm groups. Neither were there differences in relaxin levels in sera and milk between the term and preterm groups. At 6 weeks postpartum, relaxin was not measured in any sera but was measured in milk from six of eight patients in the term group and five of six patients in the preterm group. Relaxin concentrations in milk were higher in the preterm group. The presence of relaxin in milk at 6 weeks postpartum suggests a nonluteal site of synthesis.

Enzyme immunoassay of gastrin releasing peptide (GRP)-like immunoreactivity in milk

A sensitive and specific enzyme immunoassay (EIA) for gastrin releasing peptide (GRP)-like immunoreactivity was developed using enzyme-labeled antigen. The synthetic carboxy-terminal fragment of human GRP(12-27) was conjugated with beta-D-galactosidase for EIA. The minimum amount of GRP-like immunoreactivity detectable by this method was 0.24 femtomol/well (6 picomol/liter). The level of GRP-like immunoreactive substance in bovine foremilk was about 150 nanomol/liter, the level of which was more than hundredfold higher than that in normal milk or calf serum.

Isolation and identification of neuroendocrine peptides from milk

Hormone, hormone-like substances, and neuroendocrine peptides are natural constituents of milk, and they may have an important physiological and pharmacological role in neonate development. The concentration of these peptides in milk greatly exceeds those in serum and implies an active concentration mechanism in the mammary gland. The large quantities in which milk can be supplied and the development of highly efficient procedures for the purification of peptides suggest that milk may prove to be an excellent source for identifying as yet "unknown" hormones and neuroendocrine peptides.

Inflammation-related changes in cyclic AMP and cyclic GMP in bovine mastitis

Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) concentrations in milk and plasma samples from healthy and mastitic cows were determined by radioimmunoassay and compared with prostaglandins (PGE2, PGF2 alpha and thromboxane B2 [TXB2]), phospholipids and other relevant parameters in milk and blood. The concentrations of cAMP were about five times higher in plasma (p less than 0.01) than in milk, whereas the cGMP concentration in milk was three times higher (p less than 0.01) than that in plasma in both healthy and diseased animals. In mastitic milk, the cAMP and cGMP concentrations were 19% and 65% and in blood plasma 13% and 84% higher respectively than in healthy animals. In milk, cyclic nucleotide concentrations correlated with the markedly elevated cell count and also with the prostaglandin concentration and pH. In blood, cAMP correlated positively with phospholipids and cGMP with reduced glutathione (GSH). These changes are considered to be important in the disease process and, in particular, the increase in cGMP deserves further study.

Influence of bombesin on gastrointestinal and pancreatic cell growth in adult and suckling animals

Chronic administration of bombesin in the adult rat affects cell growth and enzyme activities in the pancreas. It also induces hyperplasia of the fundic mucosa, increases antral gastrin content, and stimulates gastrin cell proliferation in the antral mucosa. These effects could be explained by the release of hormones such as gastrin and CCK, whose trophic roles on the digestive tract are well proven. Some arguments raise the possibility that bombesin may also act directly on these organs (i.e., the presence of specific receptors for bombesin, pancreatic changes induced by bombesin and not blocked by a potent, specific CCK receptor antagonist). It may well be that both mechanisms exist simultaneously. In addition, bombesin has a growth-promoting effect on the gastric mucosa and pancreas of suckling rats when administered either subcutaneously or orogastrically. Keeping in mind that the maternal milk contains a bombesin-like immunoreactant peptide, we consider that the latter finding raises questions about the possible physiological role of such a peptide in the regulation of the postnatal development of the gastrointestinal tract.

Growth hormone releasing factor and somatostatin concentrations in the milk of lactating women

The concentrations of growth hormone releasing factor (GRF) and somatostatin, two hypothalamic neuropeptides involved in the regulation of growth hormone secretion, were measured in human milk samples. The study was performed in healthy women within 48 h of delivery or during established lactation (between 1 and 64 weeks post delivery). No statistically significant correlation was found between the levels in milk of either of the neuropeptides and the gestational age at birth. However, lower values of GRF (23 +/- 4.7 pg/ml vs. 40.5 +/- 4.9 pg/ml) were found in milk obtained during established lactation than in milk obtained close to delivery. A positive correlation was observed between somatostatin and GRF concentrations in milk. The possible involvement of milk neuropeptides in the control of growth hormone secretion in the neonate, as well as in the regulation of other physiological processes, are evaluated.

Human beta-casomorphin-8 immunoreactive material in the plasma of women during pregnancy and after delivery

A method for the extraction of human beta-casomorphin-8 immunoreactive material from human plasma and a radioimmunoassay for its determination in the plasma extracts were developed. Blood was collected from 34 men, from 35 non-pregnant women, from 35 pregnant women and from 138 women after delivery and plasma extracts were assayed for the presence of human beta-casomorphin-8 immunoreactive materials. No human beta-casomorphin-8 immunoreactive material was detected in the plasma of men or non-pregnant women, whereas such material was found in the plasma of 26 out of 35 pregnant women and in the plasma of 100 out of 138 women after parturition. Material collected from women after delivery was characterized by gel filtration and high-performance liquid chromatography (HPLC) and was found to be of different composition in various individuals; its components, one of which coeluted with human beta-casein from the HPLC column, have apparently higher molecular weights than human beta-casomorphin-8. Some of these compounds seem to be very stable against enzymatic degradation at 37 degrees C in human plasma, whereas human beta-casomorphin-8 proved to be degraded very fast under identical conditions. A physiological significance of mammary products of the beta-casomorphin type during pregnancy or after parturition is suggested.

Rat milk stimulates pituitary growth hormone secretion of neonatal pituitaries in vitro

Aqueous extracts of rat milk stimulated growth hormone (GH) secretion from superfused pituitaries of two-day old rats. The GH stimulatory effect of milk increased with the time elapsed postpartum; growth hormone releasing hormone and thyrotropin releasing hormone seem to be the major milk borne GH releasing factors. These results indicate that milk intake may play a role in maintaining the high plasma GH levels observed in the neonatal period.

Effects of enterally fed epidermal growth factor on the small and large intestine of the suckling rat

Epidermal growth factor (EGF) has been shown to be present in the milk of several species, including the rat, and to have gastrointestinal effects when given parenterally or orally in pharmacologic doses. We investigated the effect of enteral EGF in physiologic doses on the small intestine and colon of suckling rats. Serum thyroxine (T4) levels were also measured. Rats were gavage-fed by hand with an artificial formula with or without added EGF every 3 h from 11 to 14 days of age. Intake was adjusted to deliver 30 kcal/100 g b.wt./day of formula and 16 micrograms/kg/day of EGF approximating the daily caloric intake, and about twice the estimated daily EGF intake for suckling rats. Weight gain did not differ between groups (fed EGF: 3.8 + 0.2 g; not fed EGF: 3.7 + 0.1 g). The protein content of the whole colon of rats fed an EGF-containing formula was significantly lower and the DNA content significantly higher, than in rats fed formula without added EGF. The protein/DNA ratio was therefore markedly higher in the animals fed formula without added EGF; these effects were most evident in the distal colon. In contrast, there was no effect of EGF on small intestinal protein and DNA content; lactase, sucrase, and maltase activities were likewise unaffected, as was serum T4. These data suggest a physiologic role for breast milk EGF in the development of the suckling rat colon.

Stimulating effect of bombesin on the growth of gastrointestinal tract and pancreas in suckling rats

The current study examines the effects of bombesin on gastrointestinal and pancreatic growth in suckling rats. During a period of 6 days, 7-day-old rats were injected twice daily with bombesin tetradecapeptide (20 micrograms/kg) in hydrolyzed gelatin or with gelatin alone. At the end of bombesin treatment, the weights of stomach, intestine, and pancreas; the heights of fundic and antral mucosae; and the density of parietal cells were significantly increased over control values. The gastrin cell population also tended to be augmented. The surface of glandular stomach, the duodenal mucosal height, and the somatostatin cell population were not modified as compared to controls. Electron morphometric analysis indicates that the increase in pancreatic weight under bombesin treatment was partly due to hypertrophy of acinar cells. This was confirmed by biochemical data that also showed that hypertrophy was associated with hyperplasia. Storage of secretory granules in acinar cells of the neonate rat pancreas under bombesin treatment seemed probable. Chymotrypsinogen and trypsinogen pancreatic contents were greatly augmented; lipase and colipase contents were not affected, whereas the amylase content tended to decrease. All these findings suggest that bombesin might be a general trophic factor for the neonatal digestive system in the rat. The mechanism of its action, however, remains to be determined.

Growth hormone releasing factor-like immunoreactivity in human milk

The presence of immunoreactive growth hormone-releasing factor (GRF) in human milk has been demonstrated. By using sequential high performance liquid chromatography, it has been shown that most of the immunoreactivity co-elutes with the synthetic, hypothalamic-like, GRF (1-40). The concentrations of GRF detected (between 152 and 432 pg GRF/ml milk) exceed several fold its values in plasma.

High levels of vasoactive intestinal peptide in human milk

The presence of immunoreactive vasoactive intestinal peptide (VIP) in human milk has been demonstrated by high performance liquid chromatography and a specific radioimmunoassay. Immunoreactive VIP-like peptide co-eluted with the synthetic marker on a reversed phase C18 column. The levels of the neuropeptide ranged between 67 and 161 pg VIP/ml milk.

Demonstration of a beta-casomorphin immunoreactive material in the plasma of newborn calves after milk intake

Blood was collected from newborn calves before and after their first milk intake after birth; extracts of plasma were assayed by radioimmunoassay for the presence of beta-casomorphin-7 immunoreactive materials. No beta-casomorphin immunoreactivity was found in samples collected before milk ingestion; however, in samples collected after milk ingestion a beta-casomorphin-7 immunoreactive material was detected. Chromatographic characterization showed that this material was not identical with beta-casomorphin-7 but might rather represent a precursor thereof. The material proved resistant to enzymatic attack during a 30-min incubation period at 37 degrees C in the plasma of newborn calves, whereas beta-casomorphin-7 was degraded under these conditions. A physiological significance of beta-casomorphin-7 eventually cleaved from such a precursor material at any site in the newborn mammal is suggested.

Human breast milk stimulates rat liver cholesterol 7 alpha-hydroxylase activity in vitro

Human breast milk at concentrations of (40 microliter/ml) markedly stimulates the activity of cholesterol 7 alpha-hydroxylase (rate limiting enzyme involved in cholesterol catabolism) in rat liver microsomal preparations. This activity persisted after a) cold acetone extraction (to remove cholesterol) b) dialysis and c) boiling and trypsin treatment of milk. Homogenized cow's milk and infant formula (Similac) also possessed the stimulating activity. These results suggest that milk might provide some factor(s) for the development of cholesterol catabolic process which is immature at birth.

Immunoreactive and biologically active somatostatin in human and sheep milk

The presence of immunoreactive and biologically active somatostatin in sheep and human milk has been demonstrated. Milk somatostatin exhibits similar chromatographic behavior to that of synthetic somatostatin-14 on both reversed-phase C18 and cation-exchange high-performance liquid chromatography columns. Milk, in contrast to plasma, contains only somatostatin-14-like material. Milk somatostatin was capable of inhibiting the basal and the prostaglandin-induced release of growth hormone from anterior pituitary cell cultures in a pattern similar to synthetic somatostatin-14. The concentrations of the peptide, as determined by radioimmunoassay, were found to be 113 pg/ml in human milk and 150 +/- 4.8 pg/ml (mean +/- range) in sheep milk. These values are severalfold higher than the corresponding concentration of the peptide in the plasma of these species. These findings are analogous to our previous observations concerning two other hypothalamic hormones, luliberin and thyroliberin [Baram, T., Koch, Y., Hazum, E. and Fridkin, M. (1977) Science (Wash. DC) 198, 300-302]. The high concentration of somatostatin and other neuropeptides in milk implies either an active concentrating mechanism in the mammary gland or an additional extrahypothalamic source for the synthesis and release of these peptides.