Transforming growth factor (TGF)-alpha in human milk

Revealing the Potency of Growth Factors in Bovine Colostrum

Colostrum is a nutritious milk synthesized by mammals during the postpartum period, and its rich bioactive components has led to a global increase in the consumption of bovine colostrum as a supplement. Bovine colostrum contains key components such as immunoglobulins, oligosaccharides, lactoferrin and lysozyme. It is a special supplement source due to its natural, high bioavailability and high concentrations of growth factors. Growth factors are critical to many physiological functions, and considering its presence in the colostrum, further research must be conducted on its safe application in many bodily disorders. Growth factors contribute to wound healing, muscle and bone development, and supporting growth in children. Additionally, the molecular mechanisms have been explored, highlighting the growth factors roles in cell proliferation, tissue regeneration, and the regulation of immune responses. These findings are crucial for understanding the potential health effects of bovine colostrum, ensuring its safe use, and forming a basis for future clinical applications. This review article examines the growth factors concentration in bovine colostrum, their benefits, clinical studies, and molecular mechanisms.

New Born Calf Serum Can Induce Spheroid Formation in Breast Cancer KAIMRC1 Cell Line

Three-dimensional (3D) cell culture systems have become very popular in the field of drug screening and discovery. There is an immense demand for highly efficient and easy methods to produce 3D spheroids in any cell format. We have developed a novel and easy method to produce spheroids from the newly isolated KAIMRC1 cell line in vitro. It can be used as a 3D model to study proliferation, differentiation, cell death, and drug response of cancer cells. Our procedure requires growth media supplemented with 10% new born calf serum (NBCS) and regular cell culture plates to generate KAIMRC1 spheroids without the need for any specialized 3D cell culture system. This procedure generates multiple spheroids within a 12–24-h culture. KAIMRC1 spheroids are compact, homogeneous in size and morphology with a mean size of 55.8 µm (±3.5). High content imaging (HCI) of KAIMRC1 spheroids treated with a panel of 240 compounds resulted in the identification of several highly specific compounds towards spheroids. Immunophenotyping of KAIMRC1 spheroids revealed phosphorylation of FAK, cJUN, and E-cadherin, which suggests the involvement of JNK/JUN pathway in the KAIMRC1 spheroids formation. Gene expression analysis showed upregulation of cell junction genes, GJB3, DSC1, CLDN5, CLDN8, and PLAU. Furthermore, co-culture of KAIMRC1 cells with primary cancer-associated-fibroblasts (CAFs) showcased the potential of these cells in drug discovery application.

Metabolic Conditions Including Obesity, Diabetes, and Polycystic Ovary Syndrome: Implications for Breastfeeding and Breastmilk Composition

Breastfeeding is internationally recognized as the recommended standard for infant nutrition, informed by evidence of its multiple benefits for both mother and baby. In the context of common metabolic conditions such as polycystic ovary syndrome, diabetes (type 1, type 2, and gestational), and obesity, breastfeeding may be particularly beneficial for both mother and infant. However, there is evidence of delayed lactogenesis and reduced breastfeeding rates and duration in women with these conditions, and the effects of altered maternal metabolic environments on breastmilk composition (and potentially infant outcomes) are incompletely understood. In this review, we explore the relationships between maternal metabolic conditions, lactogenesis, breastfeeding, and breastmilk composition. We examine relevant potential mechanisms, including the central role of insulin both in lactogenesis and as a milk-borne hormone. We also describe the bioactive and hormonal components of breastmilk and how these may link maternal and infant health.

Bovine Colostrum: Its Constituents and Uses

Colostrum is the milk produced during the first few days after birth and contains high levels of immunoglobulins, antimicrobial peptides, and growth factors. Colostrum is important for supporting the growth, development, and immunologic defence of neonates. Colostrum is naturally packaged in a combination that helps prevent its destruction and maintain bioactivity until it reaches more distal gut regions and enables synergistic responses between protective and reparative agents present within it. Bovine colostrum been used for hundreds of years as a traditional or complementary therapy for a wide variety of ailments and in veterinary practice. Partly due to concerns about the side effects of standard Western medicines, there is interest in the use of natural-based products of which colostrum is a prime example. Numerous preclinical and clinical studies have demonstrated therapeutic benefits of bovine colostrum for a wide range of indications, including maintenance of wellbeing, treatment of medical conditions and for animal husbandry. Articles within this Special Issue of Nutrients cover the effects and use bovine colostrum and in this introductory article, we describe the main constituents, quality control and an overview of the use of bovine colostrum in health and disease.

Hypoallergenic infant formula lacks transforming growth factor beta activity and has a lower anti-inflammatory activity than regular infant formula

Hypoallergenic formulas are recommended for infants who are not breastfed and cannot tolerate cow milk formulas due to allergy. These formulas are hydrolyzed to break down larger protein chains into shorter, easy-to-digest, and potentially less allergenic proteins. Hydrolysis, however, possibly occurs at the expense of the transforming growth factor beta (TGF-β) and anti-inflammatory activity that is inherent in regular formula. Our objective was to determine the TGF-β and the anti-inflammatory activity of commercially available hypoallergenic and regular formulas. Human gingival fibroblasts were incubated with reconstituted formulas followed by detection of TGF-β target genes and activation of Smad2/3 signaling. Gingival fibroblasts and the oral squamous cell carcinoma cell line HSC-2 were also exposed to formulas before adding interleukin (IL)1β and tumor necrosis factor (TNF)α to provoke expression of pro-inflammatory cytokines. For murine bone marrow-derived macrophages, pro-inflammatory cytokine expression was stimulated with saliva. Changes in p65 nuclear translocation and phosphorylation of smad3 and p38 were analyzed by immunostaining. Our study demonstrated that regular formula, but not hypoallergenic formula, enhanced the expression of TGF-β target genes IL11, PRG4, and NOX4 in gingival fibroblasts. Hypoallergenic formulas also failed to initiate nuclear translocation of Smad2/3 and phosphorylation of Smad3. Moreover, regular formulas were more potent than hypoallergenic formulas in reducing the expression of pro-inflammatory cytokines in gingival fibroblasts, HSC-2 epithelial cells, and murine bone marrow macrophages. Hypoallergenic and regular formulas had a similar capacity to reduce p65 nuclear translocation and phosphorylation of p38 in fibroblasts. These findings suggest that hypoallergenic formulas lack in vitro TGF-β activity and have a lower anti-inflammatory activity compared with regular formulas.

TGF-β activity in cow milk and fermented milk products: An in vitro bioassay with oral fibroblasts

OBJECTIVE

Milk is a rich source of transforming growth factor (TGF)-β which supports intestinal mucosal homeostasis of infants. Milk may also have beneficial effects on the integrity of the oral cavity, its being part of the gastrointestinal tract. However, it is unclear if milk and fermented milk products provoke a TGF-β response in oral cells.

MATERIAL AND METHODS

Human gingival fibroblasts were exposed to pasteurized cow milk, yoghurt, sour milk, buttermilk and whey, followed by a reverse transcriptase polymerase chain reaction of the TGF-β target genes interleukin11 (IL11), proteoglycan4 (PRG4), and NADPH oxidase 4 (NOX4). Immunoassays were performed for IL11 and TGF-β in cell culture supernatant and milk products, respectively. Signaling was investigated with the TGF-β receptor type I kinase inhibitor SB431542.

RESULTS

We report here that pasteurized cow milk and the aqueous fractions of yoghurt, sour milk, buttermilk and whey enhanced the expression of IL11, NOX4 and PRG4 in gingival fibroblasts. Moreover, IL11 protein levels in the respective supernatant were significantly increased. Cow milk, yoghurt, sour milk and buttermilk contain approximately 1-2 ng TGF-β1, whereas active TGF-β1 is hardly detectable in whey. SB431542 reduced the response of gingival fibroblasts to pasteurized cow milk and fermented milk products based on IL11 release into the supernatant.

CONCLUSIONS

These results demonstrate that gingival fibroblasts respond to pasteurized cow milk and to fermented milk products with an increased expression of TGF-β target genes.

Cytokines in milk and the role of TGF-beta

Cytokines are required for normal growth and development of the mammary gland and TGF-β prominently represents an established effector of apoptosis, e.g., during involution of the mammary gland. By the control of intracellular signaling pathways, including JAK/STAT, MAPK, PI-3K, and NF-κB, cytokines efficiently regulate cell proliferation and inflammation in the breast. Therefore, cytokines are discussed also in a context of malignant mammary growth. As a group of tissue hormones produced by somatic cells or by cells from the immune system, cytokines are defined by their immunomodulatory potential. Over the past 40 years, multiple cytokines were identified in colostrum and milk. Importantly, cytokines derived from mammary secretions after birth are required for maturation of the immune system in the developing gastrointestinal tract from the suckling. Moreover, recent studies have further assessed the particular interactions between probiotic bacterial strains and cytokines. In light of the increasing prevalence of inflammatory diseases of the gastrointestinal system, the effects of probiotic microorganisms during milk fermentation may have immunotherapeutic potential in the future.

Epidermal growth factor and transforming growth factor-α in human milk of different lactation stages and different regions and their relationship with maternal diet

Epidermal growth factor (EGF) and transforming growth factor-α (TGF-α) are important growth-promoting factors in human milk and play an important role in a newborn's gastrointestinal function.

Minimal Enteral Nutrition to Improve Adaptation After Intestinal Resection in Piglets and Infants

BACKGROUND

Minimal enteral nutrition (MEN) may induce a diet-dependent stimulation of gut adaptation following intestinal resection. Bovine colostrum is rich in growth factors, and we hypothesized that MEN with colostrum would stimulate intestinal adaptation, compared with formula, and would be well tolerated in patients with short bowel syndrome.

METHODS

In experiment 1, 3-day-old piglets with 50% distal small intestinal resection were fed parenteral nutrition (PN, n = 10) or PN plus MEN given as either colostrum (PN-COL, n = 5) or formula (PN-FORM, n = 9) for 7 days. Intestinal nutrient absorption and histomorphometry were performed. In experiment 2, tolerance and feasibility of colostrum supplementation were tested in a pilot study on 5 infants who had undergone intestinal resection, and they were compared with 5 resected infants who served as controls.

RESULTS

In experiment 1, relative wet-weight absorption and intestinal villus height were higher in PN-COL vs PN (53% vs 23% and 362 ± 13 vs 329 ± 7 µm, P < .05). Crypt depth and tissue protein synthesis were higher in PN-COL (233 ± 7 µm, 22%/d) and PN-FORM (262 ± 13 µm, 22%/d) vs PN (190 ± 4 µm, 9%/d, both P < .05). In experiment 2, enteral colostrum supplementation was well tolerated, and no infants developed clinical signs of cow's milk allergy.

CONCLUSION

Minimal enteral nutrition feeding with bovine colostrum and formula induced similar intestinal adaptation after resection in piglets. Colostrum was well tolerated by newly resected infants, but the clinical indication for colostrum supplementation to infants subjected to intestinal resection remains to be determined.

Mammary Epithelial Cells Treated Concurrently with TGF-α and TGF-β Exhibit Enhanced Proliferation and Death

Transforming growth factor-α (TGF-α) stimulates while TGF-β inhibits mammary epithelial cell growth, suggesting that when cells are treated concurrently with the growth factors their combined effects would result in no net growth. However, combined treatments stimulate proliferation and cellular transformation in several cell lines. The objective of this paper was to describe the effect of long-term (6 days) concurrent TGF-α and TGF-β treatment on normal mammary epithelial cell growth pattern, morphology, and gene expression. Growth curve analysis showed that TGF-α enhanced while TGF-β suppressed growth rate until Day 4, when cells entered lag phase. However, cells treated concurrently with both growth factors exhibited a dichotomous pattern of growth marked by growth and death phases (with no intermittent lag phase). These changes in growth patterns were due to a marked induction of cell death from Day 2 (16.5%) to Day 4 (89.5%), resulting in the transition from growth to death phases, even though the combined treated cultures had significantly more ( P < 0.05) cells in S phase on Day 4. TGF-β stimulated epithelial to mesenchyme transdifferentiation (EMT) in the presence of TGF-α, as characterized by increased expression of fibronectin and changes in TGF-β receptor binding. Expression patterns of genes that regulate the cell cycle showed significant interaction between treatment and days, with TGF-β overriding TGF-α–stimulated effects on gene expression. Overall, the combined treatments were marked by enhanced rates of cellular proliferation, death, and trans-differentiation, behaviors reminiscent of breast tumors, and thus this system may serve as a good model to study breast tumorigenesis.

Human breast milk: A review on its composition and bioactivity

Breast milk is the perfect nutrition for infants, a result of millions of years of evolution, finely attuning it to the requirements of the infant. Breast milk contains many complex proteins, lipids and carbohydrates, the concentrations of which alter dramatically over a single feed, as well as over lactation, to reflect the infant's needs. In addition to providing a source of nutrition for infants, breast milk contains a myriad of biologically active components. These molecules possess diverse roles, both guiding the development of the infants immune system and intestinal microbiota. Orchestrating the development of the microbiota are the human milk oligosaccharides, the synthesis of which are determined by the maternal genotype. In this review, we discuss the composition of breast milk and the factors that affect it during the course of breast feeding. Understanding the components of breast milk and their functions will allow for the improvement of clinical practices, infant feeding and our understanding of immune responses to infection and vaccination in infants.

Bovine colostrum to children with short bowel syndrome: a randomized, double-blind, crossover pilot study

BACKGROUND

Management of short bowel syndrome (SBS) aims to achieve intestinal autonomy to prevent fluid, electrolyte, and nutrient deficiencies and maintain adequate development. Remnant intestinal adaptation is required to obtain autonomy. In the newborn pig, colostrum has been shown to support intestinal development and hence adaptive processes.

AIM

The efficacy of bovine colostrum to improve intestinal function in children with SBS was evaluated by metabolic balance studies.

MATERIALS AND METHODS

Nine children with SBS were included in a randomized, double-blind, crossover study. Twenty percent of enteral fluid intake was replaced with bovine colostrum or a mixed milk diet for 4 weeks, separated by a 4-week washout period. Intestinal absorption of energy and wet weight was used to assess intestinal function and the efficacy of colostrum.

RESULTS

Colostrum did not improve energy or wet weight absorption compared with the mixed milk diet (P = 1.00 and P = .93, respectively). Growth as measured by weight and knemometry did not differ between diets (P = .93 and P = .28). In these patients, <150% enteral energy absorption of basal metabolic rate and 50% enteral fluid absorption of basal fluid requirement suggested intestinal failure and a need for parenteral nutrition (PN).

CONCLUSION

Inclusion of bovine colostrum to the diet did not improve intestinal function. Metabolic nutrient and wet weight balance studies successfully assessed intestinal function, and this method may distinguish between intestinal insufficiency (non-PN-dependent) and intestinal failure (PN-dependent) patients.

Clinical significance of amphiregulin and epidermal growth factor in colostrum

BACKGROUND

Colostrum contains a wide variety of crucial nutritional elements including growth factors for newborn infants to adapt to the extrauterine environment.

OBJECTIVE

To investigate the clinical significance of epidermal growth factor receptor ligands in milk during the first month of lactation.

METHODS

The concentrations of epidermal growth factor (EGF), amphiregulin (AR) and transforming growth factor-α (TGF-α) in milk sampled from a total of 31 normal mothers at days 1-3, 5, and 30 postpartum were examined using ELISA.

RESULTS

At days 1-3, the concentration of EGF was extremely high [131.6 ± 20.4 (mean ± SEM) ng/ml] compared to that of AR (4,197.2 ± 1,055.2 pg/ml) or TGF-α (261.7 ± 33.6 pg/ml), while the concentration of AR was significantly elevated compared to that of TGF-α. At days 5 and 30, the concentration of EGF was significantly elevated compared to that of AR or TGF-α. In 16 mothers among the same 31 subjects, samples were longitudinally obtained on days 1, 2, 5, and 30 postpartum. Concentrations of AR were higher on days 1 and 2 and rapidly declined to below 1 ng/ml on day 5, and were maintained at lower levels on day 30. Concentrations of EGF were high on day 1 (greater than 10 ng/ml) but gradually declined by days 2, 5, and 30. Concentrations of TGF-α remained at lower levels of below 1 ng/ml throughout the lactation period from days 1 to 30.

CONCLUSION

These results suggested that EGF and amphiregulin in colostrum might contribute to the early stage of development of neonatal gastrointestinal function.

Epidermal growth factor and necrotizing enterocolitis

PURPOSE OF REVIEW

This review will summarize the clinical and experimental studies evaluating the role of epidermal growth factor (EGF) in prophylaxis and treatment of necrotizing enterocolitis (NEC).

RECENT FINDINGS

Clinical studies have suggested the importance of EGF in protection of the intestine against NEC, as well as its safety for infants suffering from NEC. The recent experimental studies identified the molecular mechanisms EGF uses for intestinal protection, which involves regulation of intestinal epithelial homeostasis and barrier function. Further studies are necessary to identify the optimal dose, timing, and route of administration of EGF to NEC patients. No clinical studies are currently underway.

SUMMARY

NEC is a devastating problem for preterm neonates, but the exact disease pathogenesis remains unclear. Growing clinical evidence supports the use of EGF as a predictive marker of NEC and its use for prevention and treatment of NEC. In addition, experimental data indicate potential mechanisms of EGF prevention against NEC. These include reduction of inflammation, improvement of barrier function, and regulation of epithelial apoptosis and autophagy.

EGFR is involved in control of gastric cell proliferation through activation of MAPK and Src signalling pathways in early-weaned rats

OBJECTIVES

Early weaning (EW) increases proliferation of the gastric epithelium in parallel with higher expression of transforming growth factor alpha and its receptor epidermal growth factor receptor (EGFR). The primary objective of the present study was to examine involvement of EGFR signalling in regulating mucosal cell proliferation during the early weaning period.

MATERIALS AND METHODS

Fifteen-day-old rats were split into two groups: suckling (control) and EW, in which pups were separated from the dam. Animals were killed daily until the 18th day, 3 days after onset of treatment. To investigate the role of EGFR in proliferation control, EW pups were injected with AG1478, an EGFR inhibitor; signalling molecules, proliferative indices and cell cycle-related proteins were evaluated.

RESULTS

EW increased ERK1/2 and Src phosphorylation at 17 days, but p-Akt levels were unchanged. Moreover, at 17 days, AG1478 administration impaired ERK phosphorylation, whereas p-Src and p-Akt were not altered. AG1478 treatment reduced mitotic and DNA synthesis indices, which were determined on HE-stained and BrdU-labelled sections. Finally, AG1478 injection decreased p21 levels in the gastric mucosa at 17 days, while no changes were detected in p27, cyclin E, CDK2, cyclin D1 and CDK4 concentrations.

CONCLUSIONS

EGFR is part of the mechanism that regulates cell proliferation in rat gastric mucosa during early weaning. We suggest that such responses might depend on activation of MAPK and/or Src signalling pathways and regulation of p21 levels.

Milk epidermal growth factor and gut protection

Maternal milk is a complex fluid, with multifunctional roles within the developing gastrointestinal tract. Epidermal growth factor (EGF) and heparin-binding EGF-like growth factor (HB-EGF) are members of the family of EGF-related peptides. Biological actions of these growth factors are mediated via interaction with the EGF-receptor (EGF-R). In the early postnatal period, breast milk is the major source of EGF for the developing intestinal mucosa. HB-EGF is also detected in breast milk, but in concentrations 2 to 3 times lower than EGF. With normal physiological conditions, the intestinal epithelium undergoes a continuing process of cell proliferation, differentiation, and maturation. EGF plays an important role in these processes. In pathophysiologic situations, EGF contributes to epithelial protection from injury and post-injury mucosal repair. Necrotizing enterocolitis (NEC) is a devastating disease affecting infants born prematurely. The pathogenesis of NEC is not known, and there is no effective treatment for this disease. In an experimental NEC model, oral administration of a physiological dose of EGF significantly reduces the incidence and severity of NEC. HB-EGF provides similar protection against NEC, but only when pharmacological doses are used. Further studies are necessary before EGF can be introduced as an efficient therapeutic approach of intestinal injury.

Intestinal hormones and growth factors: effects on the small intestine

There are various hormones and growth factors which may modify the intestinal absorption of nutrients, and which might thereby be useful in a therapeutic setting, such as in persons with short bowel syndrome. In part I, we focus first on insulin-like growth factors, epidermal and transferring growth factors, thyroid hormones and glucocorticosteroids. Part II will detail the effects of glucagon-like peptide (GLP)-2 on intestinal absorption and adaptation, and the potential for an additive effect of GLP2 plus steroids.

The prenatal porcine intestine has low transforming growth factor-beta ligand and receptor density and shows reduced trophic response to enteral diets

Transforming growth factor-beta (TGF-β) plays a role in enterocyte proliferation control, cell differentiation, and immune regulation via binding to specific TGF-β receptors (TGF-β R) in the intestinal epithelium. Endogenous TGF-β production is low in the intestine during the perinatal period, but some exogenous TGF-β ligands are supplied by amniotic fluid intake in the fetus and by colostrum ingestion in the neonate. It is not clear, however, whether luminal TGF-β receptors are present and functional at this critical time. We studied intestinal TGF-β receptors by immunohistochemistry during the last 20% of gestation in pigs and in chronically catheterized fetuses following exposure to colostrum, milk, and amniotic fluid (control). In fetal pigs, the TGF-β Rs were predominantly localized to the crypt epithelium, but staining intensity increased markedly just before term and shifted to the villous epithelium in newborn pigs, concurrently with marked increases in villous heights and crypt depths (+100–200%, P < 0.05). In contrast to previous observations in term newborn pigs, fetal pigs did not show any milk-induced change in TGF-β receptor densities or localization, although a moderate increase in villous height was observed, relative to control (+25–50%, P < 0.05). We conclude that intestinal TGF-β receptor density and localization are immature and unresponsive to TGF-β containing milk diets in prenatal pigs. Immaturity of TGF-β-mediated immune regulation may play a role in the increased sensitivity of preterm neonates to diet-induced intestinal inflammatory disorders.

Pancreatic secretory trypsin inhibitor is a major motogenic and protective factor in human breast milk

Colostrum is the first milk produced after birth and is rich in immunoglobulins and bioactive molecules. We examined whether human colostrum and milk contained pancreatic secretory trypsin inhibitor (PSTI), a peptide of potential relevance for mucosal defense and, using in vitro and in vivo models, determined whether its presence influenced gut integrity and repair. Human milk was collected from individuals over various times from parturition and PSTI concentrations determined with the use of immunoassay. Human milk samples were analyzed for proliferation and promigratory activity (wounded monolayers) and antiapoptotic activity (caspase-3 activity) with the use of intestinal HT29 cells with or without neutralizing antibodies to PSTI and epidermal growth factor (EGF). Rats were restrained and given indomethacin to induce gastric injury. Effect of gavage with human breast milk with or without neutralizing antibodies on amount of injury were compared with animals receiving a commercial formula feed. PSTI is secreted into human milk, with colostrum containing a much higher concentration of PSTI than human milk obtained later. Human milk stimulated migration and proliferation about threefold and reduced indomethacin-induced apoptosis by about 70-80%. Sixty-five percent of the migratory effect of human milk could be removed by immunoneutralization of PSTI. PSTI worked synergistically with EGF in mediating these effects. Gastric damage in rats was reduced by about 75% in the presence of human milk and was more efficacious than the formula feed (P<0.001). Protective effects of the milk were reduced by about 60% by PSTI immunoneutralization. We concluded that PSTI is secreted into human milk at concentrations that have probable pathophysiological relevance.

Common behavioral influences of the ErbB1 ligands transforming growth factor alpha and epiregulin administered to mouse neonates

Ligands for epidermal growth factor (EGF) receptor (ErbB1), such as EGF, transforming growth factor alpha (TGFalpha), and epiregulin, are enriched in body fluids and blood and regulate development of various peripheral organs. It remains however how such circulating polypeptide growth factors influence brain development and function. Here, we performed peripheral injections of TGFalpha and epiregulin to mouse neonates and evaluated immediate physical and neurochemical development and later behavioral consequences. Subcutaneous administration of TGFalpha and epiregulin increased phosphorylation of brain ErbB1, suggesting their effects on brain development. Repeated their injections similarly enhanced physical development of eyelid opening and tooth eruption during early postnatal stage and resulted in abnormal behavioral traits in the adult stage. Acoustic startle responses of mice treated with these growth factors as neonates were enhanced and prepulse inhibition was decreased without an apparent correlation between prepulse inhibition level and startle intensity. Locomotor activity and fear-learning performance with tone and context cues were not altered, however. These results suggest that circulating ErbB1 ligands in the periphery of neonates have some common influences on later behavioral traits. Abnormal ErbB1 ligand production at neonatal and potentially prenatal stages might therefore associate with neurodevelopmental disorders such as schizophrenia.

Host factors in amniotic fluid and breast milk that contribute to gut maturation

The gut represents a complex organ system with regional differences, which reflect selective digestive and absorptive functions that change constantly in response to bodily requirements and the outside milieu. As a barrier to the external environment, gut epithelium must be renewed rapidly and repeatedly. Growth and renewal of gut epithelial cells is dependent on controlled cell stimulation and proliferation by a number of signaling processes and agents, including gut peptides-both endogenous and exogenous sources. This cascade of events begins during fetal development; with the ingestion of amniotic fluid, this process is enhanced and continued during infancy and early childhood through the ingestion of human milk. Events influenced by amniotic fluid during fetal development and those influenced by human milk that unfold after birth and early childhood to render the gut mature are presented.

Epidermal growth factor reduces intestinal apoptosis in an experimental model of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease of premature infants. Although end-stage NEC is characterized histopathologically as extensive necrosis, apoptosis may account for the initial loss of epithelium before full development of disease. We have previously shown that epidermal growth factor (EGF) reduces the incidence of NEC in a rat model. Although EGF has been shown to protect intestinal enterocytes from apoptosis, the mechanism of EGF-mediated protection against NEC is not known. The aim of this study was to investigate if EGF treatment elicits changes in expression of apoptotic markers in the ileum during the development of NEC. With the use of a well-established neonatal rat model of NEC, rats were divided into the following three experimental groups: dam fed (DF), milk formula fed (NEC), or fed with formula supplemented with 500 ng/ml EGF (NEC+EGF). Changes in ileal morphology, gene and protein expression, and histological localization of apoptotic regulators were evaluated. Anti-apoptotic Bcl-2 mRNA levels were markedly reduced and pro-apoptotic Bax mRNA levels were markedly elevated in the NEC group compared with DF controls. Supplementation of EGF into formula significantly increased anti-apoptotic Bcl-2 mRNA, whereas pro-apoptotic Bax was significantly decreased. The Bax-to-Bcl-2 ratio for mRNA and protein was markedly decreased in NEC+EGF animals compared with the NEC group. The presence of caspase-3-positive epithelial cells was markedly reduced in EGF-treated rats. These data suggest that alteration of the balance between pro-and anti-apoptotic proteins in the site of injury is a possible mechanism by which EGF maintains intestinal integrity and protects intestinal epithelium against NEC injury.

The c-Jun NH2-terminal kinase is essential for epidermal growth factor expression during epidermal morphogenesis

The c-Jun NH(2)-terminal kinase (JNK) group of mitogen-activated protein kinases is activated in response to a wide array of cellular stresses and proinflammatory cytokines. Roles for JNK in the developing nervous system and T-cell-mediated immunity have been established by detailed studies of mice with compound mutations in the Jnk genes. However, little is known concerning the roles of JNK in other mammalian tissues. Mice lacking both of the ubiquitously expressed isoforms (JNK1 and -2) die during midgestation with neural tube closure defects and brain abnormalities. Here we show that JNK-deficient mice exhibit delayed epithelial development in the epidermis, intestines, and lungs. In addition, JNK-deficient mice exhibit an eyelid closure defect associated with markedly reduced epidermal growth factor (EGF) receptor function, and loss of expression of the ligand EGF. We further demonstrate that adult mice lacking either JNK1 or -2 display striking differences in epidermal proliferation and differentiation, indicative of distinct roles for these kinases in the skin. We conclude that JNK is necessary for epithelial morphogenesis and is an essential regulator of signal transduction by the EGF receptor in the epidermis.

Epidermal growth factor and necrotizing enterocolitis

As the number of extremely low-birth-weight infants increases,necrotizing enterocolitis remains a critical eminent problem. Supplementation of enteral feeds with biologically active substances normally present in breast milk, such as epidermal growth factor, seems to be a logical and safe way to reduce the incidence of intestinal inflammation and necrotizing enterocolitis. Continuing basic research and clinical studies are essential before epidermal growth factor can be introduced as an efficient therapeutic approach in the treatment of neonatal necrotizing enterocolitis.

Increased epidermal growth factor levels in human milk of mothers with extremely premature infants

Maternal milk is the major source of nutrients and growth-promoting substances in the first weeks of life for the majority of neonates. Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) are trophic peptides present in human milk with significant healing effects on injured gastrointestinal mucosa. Decreasing gestational age of neonates is associated with higher risk of developing gastrointestinal disorders, and human milk provides better protection against these diseases compared with formula. The aim of this study was to evaluate the concentrations of EGF and TGF-alpha in human milk collected from mothers with infants born: extremely preterm, preterm, and full term. Milk samples were collected at the end of first, second, and fourth week postpartum from each mother of infants born in one of the three gestational age groups: extremely preterm (23-27 wk, n = 16), preterm (32-36 wk, n = 16), and full term (38-42 wk, n = 15). Milk concentrations of EGF and TGF-alpha were quantified with a homologous RIA in the milk aqueous fraction. Concentrations of EGF in human milk from the extremely preterm group (23-27 wk) were significantly higher compared with values from the preterm and full-term groups throughout the first month of lactation. A similar pattern was observed with human milk TGF-alpha; however, milk TGF-alpha levels were lower than EGF. In conclusion, we have found higher concentrations of EGF and TGF-alpha in human milk of mothers with extremely preterm babies. These data may indicate the potential importance of milk-borne EGF and TGF-alpha for the development of extremely premature infants.

The effect of pasteurization on transforming growth factor alpha and transforming growth factor beta 2 concentrations in human milk

Transforming growth factor alpha (TGF-alpha) and beta 2 (TGF-beta2) are present in human milk and are involved in growth differentiation and repair of neonatal intestinal epithelia. Heat treatment at 56 degrees C has been shown effective for providing safe banked donor milk, with good retention of other biologically active factors. The purpose of our study was to determine the effect of heat sterilization on TGF-alpha and TGF-beta2 concentrations in human milk. Twenty milk samples were collected from 20 lactating mothers in polypropylene containers and frozen at -20 degrees C for transport or storage. Before heat treatment by holder pasteurization, the frozen milk was thawed and divided into 1-mL aliquots. All samples were heated in an accurately regulated water bath until a holding temperature was achieved, then held for 30 minutes using constant agitation. Holding temperature ranged from 56.5 degrees C to 56.9 degrees C. The milk was then stored at 4 degrees C overnight for analysis the following day. The concentration of TGF-alpha was measured by radioimmunoassay. Mean concentration +/- SD of TGF-alpha in raw milk samples was 119+/-50 pg/mL, range 57 to 234. The mean concentration +/- SD of TGF-alpha in heat treated samples was 113+/-50 pg/mL, range 51 to 227. TGF-alpha concentration was minimally affected by pasteurization, with an overall loss of 6.1%. Of 19 samples, 4 had increased and 15 had decreased concentrations after pasteurization (mean percent SEM: 94%+/-7% of raw milk, range 72%+/-107%). The concentration of acid-activated TGF-beta2 was measured by enzyme-linked immunosorbent assay. Mean concentration +/- SD of TGF-beta2 in raw milk samples was 5624+/-5038 pg/mL, range 195 to 15480. The mean concentration +/- SD of TGF-beta2 in heat-treated samples was 5073+/-4646 pg/mL, range 181 to 15140. TGF-beta2 survived with relatively little loss (0.6%): of 18 samples, 11 had increased and 7 had decreased concentrations after pasteurization (mean percent +/- SEM: 99.4+/-6.7% of raw milk, range 79%-120%). In conclusion, both TGF-alpha and TGF-beta2 were well-preserved in whole milk after holder pasteurization at 56.5 degrees C. The relative increase in growth factor concentration in some of the samples may be attributable to the release of that factor from the cellular and/or fat compartments into the aqueous fraction of human milk. These findings have implications regarding use of donor milk as an alternate source of growth factors and cytokines for the newborn gut when mother's milk is unavailable.

Human lactiferous mammary gland cells produce vascular endothelial growth factor (VEGF) and express the VEGF receptors, Flt-1 AND KDR/Flk-1

Human milk contains a variety of growth factors. Recently, it was reported that vascular endothelial growth factor (VEGF) was one of them. We investigated milk VEGF isoforms, their functions, and VEGF receptors on mammary gland epithelial cells (MEC). The VEGF concentration in human milk was 74.3+/-34.9ng/ml on the first day after delivery, and rapidly decreased in a couple of days to 6.2+/-2.3ng/ml on the fifth day, and matured milk maintained about 4ng/ml. In an MTT assay, human milk accelerated HUVEC proliferation and MV303, a neutralizing antibody of VEGF, blocked 17.3 % of the effect. Immunoprecipitation and Western blotting showed that VEGF121 and VEGF165 were contained in human colostrums, and RT-PCR of human MEC confirmed that VEGF121, VEGF165 and VEGF189 were present. By immunostaining of human breast tissues, RT-PCR of MEC from human colostrum and measurement of the VEGF concentrations of conditioned media of cultured human MEC, it was confirmed that VEGF was produced by MEC. MEC was also expressed VEGF receptors, flt-1 and Flk-1/KDR. These results speculate us that the existence of autocrine or paracrine system within breast tissue via VEGF receptors on MEC and have a role in lactation.

Identification of Cripto-1 in human milk

Cripto-1 (CR-1) is an epidermal growth factor (EGF)-related peptide that plays an important role in normal mammary gland development. CR-1 is expressed in the growing terminal end buds in the virgin mouse mammary gland and its expression increases during pregnancy and lactation. Furthermore, CR-I is involved in the early stages of mouse mammary tumorigenesis and in the pathogenesis of human breast cancer. Since CR-1 is expressed in the mouse mammary gland at high levels during pregnancy and lactation, we have evaluated whether this protein is present in human milk. In the present study we demonstrate that a 28 kDa immunoreactive CR-1 protein is present in 24 human milk samples as assessed by western blot analysis and that by enzyme-linked immunosorbent assay the concentration of CR-1 ranges between 62 and 118 ng/ml. In addition, CR-1 that had been purified from human milk is able to stimulate the phosphorylation of mitogen activated protein kinase in nontransformed NMuMG mouse mammary epithelial cells. These results suggest that CR-1 in human milk may be important in regulating mammary gland development during pregnancy and lactation.

Colostrum and milk-derived peptide growth factors for the treatment of gastrointestinal disorders

Colostrum is the specific first diet of mammalian neonates and is rich in immunoglobulins, antimicrobial peptides, and growth factors. In this article we review some of these constituents of human and bovine colostrum in comparison with those of mature milk. Recent studies suggest that colostral fractions, or individual peptides present in colostrum, might be useful for the treatment of a wide variety of gastrointestinal conditions, including inflammatory bowel disease, nonsteroidal antiinflammatory drug-induced gut injury, and chemotherapy-induced mucositis. We therefore discuss the therapeutic possibilities of using whole colostrum, or individual peptides present in colostrum, for the treatment of various gastrointestinal diseases and the relative merits of the 2 approaches.

Effect of human milk fortifier on the immunodetection and molecular mass profile of transforming growth factor-alpha

OBJECTIVE

To determine if the addition of human milk fortifier (HMF) affects the distribution, immunoreactivity, or molecular mass profile of transforming growth factor-alpha (TGF-alpha) within the compartments of human milk.

METHODS

Fifteen milk samples were obtained. Each sample was divided into two aliquots; a powdered HMF was added to the first aliquot. TGF-alpha concentration was measured via radioimmunoassay in whole milk and its aqueous and fat fractions +/- HMF. TGF-alpha molecular mass profiles of the samples (v/v) were measured via Western blotting.

RESULTS

TGF-alpha concentration (mean +/- SD) in fortified whole milk (15.7 +/- 7.1 pg/100 microl) vs. nonfortified whole milk (14.8 +/- 8.0 pg/100 microl) and in the aqueous fraction of fortified (14.0 +/- 2.7 pg/100 microl) vs. nonfortified (14.0 +/- 3.5 pg/100 microl) did not differ statistically. There was, however, a marked decrease in the concentration of TGF-alpha in the fat fraction of fortified (30.6 +/- 2.8 pg/100 microl) vs. nonfortified (98.0 +/- 6.9 pg/100 microl) milk samples. Western blot for TGF-alpha in whole milk and its separated fractions revealed characteristic bands at 6.5, 12-16, 22, 26-30 and 46 kD. HMF alone and HMF with sodium taurocholate had a prominent band at 18 kD and fainter bands at 6.5, 26-30, and 46 kD. While whole and aqueous milk samples with HMF also consistently showed the 18-kD band, in 8/15 fat fraction samples with HMF the 18-kD band was nondetectable and was only faintly detectable in the remaining 7/15 samples.

CONCLUSIONS

It appears that HMF differentially alters the biochemical profile of human milk with regard to TGF-alpha concentration and molecular mass profile. What effect this alteration in human milk biochemistry has on neonatal gut function remains unknown.

Human milk as a carrier of biochemical messages

Not only does breast milk provides an ideal nutrient composition for the newborn, but it also contains a variety of substances that may actively influence growth and development of the infant and stimulate neonatal protection against gastrointestinal diseases. Hormones, growth factors, cytokines and even whole cells are present in breast milk and act to establish biochemical and immunological communication between mother and child. In addition, milk nutrients such as nucleotides, glutamine and lactoferrin have been shown to influence gastrointestinal development and host defense. The unique properties of milk as a mediator of biochemical messages will be presented and the clinical significance of breastfeeding in the prevention of neonatal gastrointestinal diseases will be discussed.

Expression of functional immunomodulatory and anti-inflammatory factors in human milk

In addition to well-recognized antimicrobial substances, a growing body of evidence has accrued during the last decade regarding the presence and function of immunomodulatory and anti-inflammatory factors present in human milk and their role in protecting the mature newborn as well as the premature infant against infections. In addition, it is now appreciated that a number of these factors present in human milk may actively modulate the synthesis and maturation of the recipient immune system. This complex and interactive system of bioactive substances in human milk appears ideally to be designed to function by noninflammatory mechanisms, to operate often in a complementary or synergistic manner, to resist the digestive process in the recipient gastrointestinal tract, and to supplement developmentally delayed immune factors of the infant. The in vivo fate and effects of these immune factors in human milk, however, are still poorly understood. Clinical studies in conjunction with a broader use of experimental animal models and basic research are needed in the future to address these questions.

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.

Soluble transforming growth factor-alpha is present in the pulmonary edema fluid of patients with acute lung injury

Recent in vivo and in vitro experimental evidence indicates that transforming growth factor-alpha (TGF-alpha) is an important growth factor in the process of recovery and remodeling that occurs after acute lung injury. However, there are very little clinical data on TGF-alpha in patients with acute lung injury. Therefore, the purpose of this study was to determine if TGF-alpha is present in biologically significant concentrations in the pulmonary edema fluid from patients with acute lung injury, and to determine if the presence of TGF-alpha is specific for acute lung injury by including control patients with hydrostatic edema. Using an enzyme-linked immunosorbent assay, plasma and pulmonary edema fluid TGF-alpha levels were measured in 43 patients (34 with increased permeability edema, nine with hydrostatic edema). TGF-alpha was detected in 24 of 34 patients (71%) with increased permeability pulmonary edema (range, 0.035 to 2.57 ng/mL) compared with only two of nine patients with hydrostatic edema (p < 0.05). TGF-alpha was not detected in any plasma samples. These concentrations of TGF-alpha in pulmonary edema fluid have potent in vivo and in vitro effects on alveolar epithelial sodium transport and alveolar epithelial cell motility. In conclusion, biologically relevant concentrations of soluble TGF-alpha are present in the pulmonary edema fluid on day 1 of patients with acute lung injury, a remarkable finding with important implications for the repair and resolution of acute lung injury, particularly since TGF-alpha was detected so early in the course of acute lung injury.

Identification and partial purification of a basic fibroblast growth factor-like growth factor derived from bovine colostrum

Bovine colostrum that had been collected up to 6 h postpartum was fractionated by ammonium sulfate precipitation, and various fractions were examined for basic fibroblast growth factor activity. Activity that stimulated cell growth was detected in the cream fraction, which was purified by isoelectric focusing and heparin affinity chromatography. Three peaks were eluted from the heparin affinity column at approximately 0.5, 1, and 1.75 M NaCl. Although activity that stimulated cell growth was detected in the second and third peaks, a reaction with antibasic fibroblast growth factor antibody was observed only in the third peak. Fractions in the second and third peaks were examined by SDS-PAGE and Western blot analysis. Activity that stimulated cell growth was detected in the second and third peaks; however, after Western blot analysis using antibasic fibroblast growth factor, only the third peak yielded positive bands at 15 and 28 kDa. These fractions were further subjected to a neutralization test using antibasic fibroblast growth factor antibody. The activity that stimulated cell growth in the second peak was virtually unchanged; however, the activity in the third peak was diminished, showing a relative activity of less than 10% at 1.25 micrograms/ml. Therefore, neutralization of the activity that stimulates cell growth by antibasic fibroblast growth factor antibody suggests that the third peak, which was eluted at approximately 1.5 to 2 M NaCl in heparin affinity chromatography, might be a basic fibroblast growth factor-like growth factor.

Transforming growth factor-alpha overexpression in proliferative verrucous leukoplakia and oral squamous cell carcinoma: an immunohistochemical study

Proliferative verrucous leukoplakia is a unique type of oral leukoplakia that has a high risk of malignant transformation. The aim of this study was to examine the expression of transforming growth factor-alpha in proliferative verrucous leukoplakia, oral squamous cell carcinoma, and normal mucosa. Transforming growth factor-alpha, a potent mitogen, is known to play an important role in various neoplasms including oral squamous cell carcinoma. Immunohistochemical localization of transforming growth factor-alpha in archival paraffin-embedded sections was performed with commercially available monoclonal antibodies. Ten cases each of normal mucosa, proliferative verrucous leukoplakia, and oral squamous cell carcinoma were stained. Quantification of the staining intensity, expressed as the cytoplasmic optical density, was done with the Roche Image Analysis System. The data were statistically analyzed with the one-way analysis of variance and Tukey tests. Notably, the mean cytoplasmic optical density of proliferative verrucous leukoplakia was significantly higher than the mean cytoplasmic optical density of normal mucosa (p < 0.01). The mean cytoplasmic optical density of proliferative verrucous leukoplakia was slightly higher than that of oral squamous cell carcinoma, however, this difference was not significant (p > 0.05). The mean cytoplasmic optical density values demonstrate that increased transforming growth factor-alpha immunoreactivity occurs in proliferative verrucous leukoplakia and oral squamous cell carcinoma relative to normal mucosa.

Cytokines in human milk: properties and potential effects upon the mammary gland and the neonate

Epidemiologic and immunologic studies of breastfed and nonbreastfed infants and investigations of certain biologic activities in human milk led to the identification of immunomodulating agents in human milk. Among them were the cytokines interleukin-1 beta (IL-1 beta); IL-6, IL-8, IL-10, granulocyte-colony stimulating factor, macrophage-colony stimulating factor (M-CSF), tumor necrosis factor-alpha, interferon-gamma, epithelial growth factor (EGF), transforming growth factor-alpha (TGF-alpha), and TGF-beta 2. Interferon-gamma may originate from T cells in milk; EGF, TGF-alpha, TGF-beta, M-CSF, IL-6, and IL-8 may be produced by mammary gland epithelium. Based upon their known functions, we hypothesize that cytokines influence the development and immunologic function of the mammary gland and the neonate. Those in vivo functions remain to be defined by future investigations.

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.

Immunolocalization of transforming growth factor alpha in normal human tissues

Transforming growth factor alpha (TGF-alpha) is a polypeptide with well-characterized growth promoting properties. The effects are exerted through the epidermal growth factor receptor (EGF receptor), which is present on many different kinds of cells. The growth factor was initially shown to induce anchorage-independent growth of normal cells and was, therefore, considered as an "oncogenic" growth factor. Later, its immunohistochemical presence in normal human cells as well as its biological effects in normal human tissues have been demonstrated. The aim of the present investigation was to elucidate the distribution of the growth factor in a broad spectrum of normal human tissues. Indirect immunoenzymatic staining methods were used. The polypeptide was detected with a polyclonal as well as a monoclonal antibody. The polyclonal and monoclonal antibodies demonstrated almost identical immunoreactivity. TGF-alpha was found to be widely distributed in cells of normal human tissues derived from all three germ layers, most often in differentiated cells. In epithelial cells, three different kinds of staining patterns were observed, either diffuse cytoplasmic, cytoplasmic in the basal parts of the cells, or distinctly localized adjacent to the nucleus, usually on the luminal aspect, corresponding to the localization of the Golgi complex. The latter staining pattern was seen predominantly in secretory epithelial cells. The present study thus confirms previous studies and elaborates new localizations of TGF-alpha in normal human tissues by investigating a broad spectrum of tissues in detail.

Epithelial immaturity and multiorgan failure in mice lacking epidermal growth factor receptor

Since the discovery that epidermal growth factor (EGF) can accelerate opening of the eyelids, the EGF receptor (EGF-R) has been extensively studied and is now considered to be a prototype tyrosine kinase receptor. Binding of EGF or of transforming growth factor-alpha (TGF-alpha) or other related factors activates the receptor and induces cell proliferation and differentiation. Although it is not found on haematopoietic cells, the EGF-R is widely expressed in mammals and has been implicated in various stages of embryonic development. Here we investigate the developmental and physiological roles of this receptor and its ligands by inactivating the gene encoding EGF-R. We find that EGF-R-/- mice survive for up to 8 days after birth and suffer from impaired epithelial development in several organs, including skin, lung and gastrointestinal tract.

Hormonally active peptides in human milk

Human milk contains many hormone and hormone-like peptides. The gastrointestinal tract of newborn infants exhibits lower proteolytic activity than in adults and higher "permeability" for macromolecules. Studies in experimental animals demonstrate that several peptides (epidermal growth factors, insulin-like growth factor I and bombesin) after orogastric administration exhibit effects on the small intestine and other organs (liver or pancreas). Few studies performed in human neonates suggest a "survival" of epidermal growth factor in their gastric content. Further studies are needed to evaluate the role of milk-borne hormonally active peptides. This need is stressed by the fact that several of those known to be present in human milk were found to be low or not detectable in infant formulae (epidermal growth factor, insulin-like growth factor I, insulin, parathyroid hormone-related peptide.

In vivo and in vitro growth-stimulatory effects of pigeon milk

Pigeon milk (PM) was tested for its effect on growth in vivo and in vitro. Eleven-day-old mice sucklings given a supplementary feeding of 125 mg PM per day for 3 days showed a significant increase in the weight of stomach and distal intestine, and the length of small intestine; there was, however, a significant decrease in heart size. In PM-fed animals the protein content of stomach, and RNA content of stomach, caecum and distal intestine increased whereas protein content of testes and distal intestine and DNA content of stomach decreased. Crude homogenates of PM stimulated 3H-thymidine incorporation both in quiescent mouse embryo fibroblasts and Chinese hamster ovary cells. Addition of PM homogenates to cell cultures increased cell number but not protein content. The extent of in vitro growth-stimulation by 1% (v/v) PM homogenate was comparable to that by 2% (v/v) foetal bovine serum but was greater than that by 0.1 ng mouse epidermal growth factor. It appears that in mammalian test systems the in vitro growth-stimulatory effects of pigeon milk outweigh those observed in mice.