Filling the gut activates paradoxical sleep in suckling rats

Recent studies with rat pups suggest that suckling and sleeping are coordinated through milk-related events in the gut. Our experiments revealed that suckling rats respond to milk in the upper gastrointestinal tract by displaying more paradoxical sleep (PS) as the volume increases to 4% of the pup's body weight. Conversely, gastric loads larger than 4% reduced PS as a function of the volume. We also discovered that filling the stomach with warm non-nutritive paraffin is as effective as an equivalent volume of warm milk for enhancing PS. Although the temperature of the gut load did not appear to play a major role in the amount of PS displayed, increasing ambient temperature from 22 degrees C to 32 degrees C increased PS significantly. Moreover, a gut load of milk (4% body weight) was more effective than the same volume of water or no load for enhancing PS. Gut loads that stay in the stomach and warm ambient temperature appear to work in an additive manner to enhance PS. The electrophysiological data together with the stomach volume data and behavioral observations of nipple attachment revealed that milk-related stimuli along the gastrointestinal tract, especially gastric distension, alter sleep patterns in predictable ways that permit us to distinguish postingestive satiety from a deprivation state and nimiety in suckling rats.

Diurnal rhythm of melatonin in bovine milk: pharmacokinetics of exogenous melatonin in lactating cows and goats

We investigated whether the melatonin levels in bovine milk exhibit a similar daily rhythm as serum levels. In 4 Ayrshire cows at the beginning of the lactation period in May the nocturnal rise in milk melatonin was moderate (from 7 +/- 2 pg/ml at noon to 15 +/- 1 pg/ml at night; mean +/- SEM) and did not correlate well with the melatonin level in serum (from 7 +/- 2 pg/ml to 27 +/- 7 pg/ml, respectively). On the other hand, 6 cows in a later phase of lactation, studied in February, showed a clear long-lasting nocturnal melatonin increase both in serum (from 9 +/- 1 pg/ml at noon to 26 +/- 3 pg/ml at night) and in milk (from 12 +/- 5 pg/ml to 26 +/- 7 pg/ml, respectively). Melatonin kinetics during lactation was studied in more detail in 4 Ayrshire cows and 4 dairy goats by giving an intravenous bolus injection of melatonin. A 3-compartment model with melatonin elimination from the central compartment was used to describe the data. The values (mean +/- SD) for the cows and the goats were: elimination half-life 27 +/- 4 min and 27 +/- 1 min, mean residence time 24 +/- 4 min and 18 +/- 4 min, steady state distribution volume 1.0 +/- 0.3 l/kg and 0.6 +/- 0.1 1/kg (p < 0.05), and plasma clearance 0.044 +/- 0.004 l/kg/min and 0.035 +/- 0.011 l/kg/min, respectively. Following injection, the melatonin concentration in milk increased rapidly and exceeded the corresponding serum value 15-30 min later, remaining thereafter above the serum level. Our results suggest that milk melatonin levels reflect blood concentrations of melatonin with a short delay.

Experimental study of the first suckling episode: rat pups ingest fluids through a surrogate nipple

The present study reported a new technique in which pups ingested fluids from a surrogate nipple. Cesarean-delivered pups tested before suckling experience showed oral grasp responses and ingested milk from the surrogate nipple. Pups ingested equal amounts of distilled water and milk and rejected saline. After ingesting milk from the surrogate nipple, pups remained attached to an empty surrogate nipple, while pups exposed to distilled water or saline did not show sustained attachment. Brief experience with milk from an oral cannula or from a surrogate nipple elicited sustained attachment to an empty nipple. Pups ingesting milk from a surrogate nipple showed increased intake of water and saline from the nipple when tested subsequently. The surrogate nipple provides a new technique for experimental study of early suckling behavior. The results suggest that initial experiences with milk may reinforce components of early suckling behavior.

Lactose intolerance associated with fractures of weight-bearing bones in Finnish women aged 38-57 years

Lactose intolerance (LI) often results in decreased calcium intake. To test if long-term low intake of calcium affects bone strength, we examined fracture risks related to LI in women aged 38-57 years. The 11,619 Finnish women aged 47-56 years who responded to the baseline postal inquiry of the Kuopio Osteoporosis Risk Factor and Prevention Study in 1989 formed the study population. In all, 896 women reported LI and 1299 women reported a fracture in 1980-1989. Current intake of dairy calcium was lower in women with LI (570 mg/d) than in the other women (850 mg/d) (p < 0.0001). The fracture risk in general was slightly elevated in women with LI compared with the other women, with an odds ratio (OR) (95% CI) of 1.33 (1.09-1.62). However, the fractures at the three most common sites (wrist, ankle, and rib) were not related to LI. In contrast, fractures at the tibia and metatarsal were strongly related to LI with ORs of 3.31 (1.51-7.24) and 2.84 (1.47-5.50), respectively. The adjusted OR for nonankle lower body fractures combined was 2.15 (1.53-3.04), whereas that for all upper body fractures combined was 1.15 (0.88-1.54). The 10 women with LI and a tibial or metatarsal fracture showed a 19% lower femoral BMD than all the other women in the densitometry subsample of 3222 women (p < 0.001). Long-term premenopausal calcium deficiency differentially affects bones with weight-bearing nonankle bones being at the greatest risk of suffering reduced strength.

Comparison of various transport media on human periodontal ligament cell viability

The purpose of this study was to determine the ability of various solutions to maintain human periodontal ligament cell (PDL) viability in vitro. PDL cells were obtained from extracted third molars and premolars of healthy individuals. These cells were placed into 24-well culture plates containing milk, Save-A-Tooth, Save-A-Tooth supplemented with platelet-derived growth factor-BB (PDGF), or Gatorade at a concentration of approximately 80,000/well. Cells left dry served as negative controls, and cells placed in Eagles' Minimal Essential Medium served as positive controls. At 1, 2, 4, 8, and 12 h, cell viability was evaluated using an MTS assay and an ELISA plate reader to determine optical density. ANOVA and Student-Newman-Keuls tests indicated that milk and Save-A-Tooth with PDGF are suitable as transport medium for avulsed teeth and that the addition of PDGF to Save-A-Tooth may enhance its ability to maintain PDL cell viability. They also suggests that Gatorade would be unsuitable as a transport medium.

[A closer look at the milking machine]

Machine milking has changed enormously in the past decades. The simple milking machine developed at the end of the nineteenth century has become a complex appliance which removes milk from the udder in a fast and efficient way. There is no doubt about the importance of a well functioning milking machine as regards milk quality and udder health. This article reviews the literature on the basic mechanics of machine milking, with special emphasis on the action of the cluster during milking. The movement of the teat cup liner is particularly important in influencing the efficiency of milk extraction and udder health. Therefore special attention is paid to the operation of the liner, how it works, and how the opening and closing of the liner affects the milking process. The functioning of the pulsator, the vacuum fluctuations occurring during milking, and the effect of these fluctuations on the opening and closing of the liner are discussed. The maintenance of the milking machine is also described.

Role of milk-borne vs endogenous insulin-like growth factor I in neonatal growth

Neonatal pigs are characterized by a high efficiency of nutrient utilization and rapid growth rate. The utilization of dietary protein for lean tissue growth is particularly efficient in neonatal pigs and is associated with a high rate of skeletal muscle protein synthesis and deposition. In support of these high growth rates, neonatal pigs consume a milk diet that has a high biological value and is abundant in growth factors, including insulin and IGF-I. During the neonatal period, there are developmental changes in the circulating concentrations of, and tissue responsiveness to, hormones, particularly insulin, IGF-I, and growth hormone that play a central role in growth regulation. Our goal has been to characterize the dietary factors and specific aspects of endocrine function that are responsible for the anabolic stimulus that helps to sustain the high rates of protein deposition in neonatal pigs. Our results suggest that, despite the abundance of growth factors in milk and colostrum, the intake of nutrients is the primary anabolic stimulus for protein synthesis and this response declines with age. There is, however, a nonnutritive and as-yet-unidentified component in colostrum that provides a specific anabolic stimulus for skeletal muscle in newborns, but this is probably neither insulin nor IGF-I. Our studies also indicate that circulating concentration of IGF-I are not a primary stimulus of skeletal muscle protein synthesis and that the primary endocrine signal that mediates the response to nutrient intake may be insulin. Future research should address how the local expression of IGF and the function of insulin and IGF receptors affect the responsiveness of anabolic processes to nutrient intake and hence the efficiency of neonatal growth.

Time course of milk accumulation-induced opening of mammary tight junctions, and blood clearance of milk components

Eight cows in early lactation were used to study the effect of milk accumulation on the state of mammary tight junctions and to examine alpha-lactalbumin as an indicator of tight junction permeability in vivo. During three successive periods, the cows were milked twice (4 days), once (6 days), and twice daily (4 days). Plasma lactose, alpha-lactalbumin, and milk sodium concentrations were used as indicators of tight junction permeability. Furthermore, four cows were used to study the clearance of lactose and alpha-lactalbumin from the blood. Milk yield during once-daily milking decreased by 15.4% (P < 0.001). All indicators of mammary tight junction patency increased (P < 0.05) transiently during once-daily milking and indicated that tight junctions opened after approximately 18 h. Plasma alpha-lactalbumin and lactose were highly correlated (r = 0.82, P < 0.001), indicating the suitability of plasma alpha-lactalbumin as an indicator of tight junction status in vivo. Clearance of alpha-lactalbumin and lactose from the blood was best described by a biexponential model. Elimination half-lives for lactose and alpha-lactalbumin were 44 and 40 min, respectively. This study showed that milk stasis during early established lactation induces tight junctions to switch to a leaky state after approximately 18 h and to revert to the closed state shortly after milking.

Milk accumulation triggers apoptosis of mammary epithelial cells

Continuous milk production is a consequence of a complex interplay of lactogenic hormones and it depends on the suckling stimulus during lactation. Involution is associated with a massive engorgement of the gland with milk followed by apoptosis of secretory epithelial cells and a restructing of the gland. Sealing of a single gland during lactation is sufficient to induce an initial engorgement and a subsequent collapse of alveolar structures and massive epithelial cell death while the other glands of the same animal remain morphologically and functionally in a lactating state. Many markers of involution such as sulfated glycoprotein-2, protein kinase A, transcription factor AP-1 and most notably stromelysin are induced in sealed glands. These findings suggest a cell death pathway which is independent of the systemic levels of lactogenic hormones but which is triggered by an accumulation of apoptosis-inducing factors in the milk, in the lobulo-alveolar structures or by a physical distortion of secretory epithelial cells generated by the engorgement.

The effects of early antibiotic treatment following diagnosis of mastitis detected by a change in the electrical conductivity of milk

Mastitis was induced experimentally by infusion of Streptococcus uberis or Staphylococcus aureus into the mammary glands of lactating dairy cows. Clinical mastitis was identified when clots appeared in foremilk (conventional diagnosis) or was predicted by changes in the electrical conductivity of foremilk (early diagnosis). The responses to intramammary antibiotic treatment that was initiated after early diagnosis of mastitis and after conventional diagnosis were compared. Early treatment significantly limited the severity of the disease and, in many cases, prevented the appearance of any visible signs of infection. Milk yield was less depressed, and the somatic cell count (SCC) was lower, when treatment was initiated earlier. The SCC of the quarter at the time mastitis was predicted was approximately 2 x 10(6) cells/ml for both pathogens, which was significantly less than when clots appeared at conventional diagnosis, approximately 4 x 10(6) and 12 x 10(6) cells/ml for Staph. aureus and Strep. uberis, respectively. The time required for SCC to recover to < 4 x 10(5) cells/ml was significantly less, approximately half, for both pathogens following early detection and early initiation of treatment. When treatment was administered in response to early detection, the bacteriological and clinical cure was almost complete, and the amount of antibiotic used was < or = 50% less. Obvious benefits for milk yield and quality and the health of the cow would result when changes in the electrical conductivity of milk are used to predict clinical mastitis and when treatment is initiated early.

Sequence variations in the bovine growth hormone gene characterized by single-strand conformation polymorphism (SSCP) analysis and their association with milk production traits in Holsteins

Sequence variations in the bovine growth hormone (GH) gene were investigated by single strand conformation polymorphism (SSCP) analysis of seven amplified fragments covering almost the entire gene (2.7 kb). SSCPs were detected in four of these fragments and a total of six polymorphisms were found in a sample of 128 Holstein bulls. Two polymorphisms, a T-->C transition in the third intron (designated GH4.1) and an A-->C transversion in the fifth exon (designated GH6.2), were shown to be associated with milk production traits. GH4.1c/GH4.1c bulls had higher milk yield than GH4.1c/GH4.1t (P < or = 0.005) and GH4.1t/GH4.1t (P < or = 0.0022) bulls. GH4.1c/GH4.1c bulls had higher kg fat (P < or = 0.0076) and protein (P < or = 0.0018) than GH4.1c/GH4.1t bulls. Similar effects on milk production traits with the GH6.2 polymorphism were observed with the GH6.2a allele being the favorable allele. The average effects of the gene substitution for GH4.1 and GH6.2 are similar, with +/-300 kg for milk yield, +/-8 kg for fat content and +/-7 kg for protein content per lactation. The positive association of GH4.1c and GH6.2a with milk production traits may be useful for improving milk performance in dairy cattle.

Effects of selenium and vitamin E administration during a late stage of pregnancy on colostrum and milk production in dairy cows, and on passive immunity and growth of their offspring

OBJECTIVE

To determine effects of selenium (Se) and vitamin E (VE) administration in late pregnancy on Se status, plasma immunoglobulin concentrations, and colostrum and milk production of dairy cows, and on Se status, passive immunity, and growth of their offspring.

ANIMALS

25 Holstein cows and their offspring.

PROCEDURE

3 and 1.5 weeks before calving, sodium selenite (5 mg/100 kg of body weight) and d,l-alpha-tocopheryl acetate (25 IU/100 kg) were administered to 13 cows. The other 12 cows were not treated. Se status was assessed by measurement of glutathione peroxidase activity of erythrocytes (GSH-Px-E).

RESULTS

The 13 treated cows had higher (P < 0.01) GSH-Px-E values at calving and during the first 12 weeks of lactation. Changes in plasma immunoglobulin concentrations before or after calving did not differ between the 2 groups of cows. During the first 36 hours after calving (4 milkings), treated cows produced 22% more colostrum than did their nontreated counterparts (P < 0.005). Percentages of colostral immunoglobulins did not differ between the 2 groups. During the first 12 weeks of lactation, treated cows produced 10% more milk than did nontreated cows (P < 0.005). GSH-Px-E values at birth and 28 days of life were significantly higher in calves from treated cows. Plasma immunoglobulin concentrations and body weight during the first 56 days after birth did not differ between calves born to treated or nontreated cows.

CONCLUSIONS AND CLINICAL RELEVANCE

Cows given Se and VE in late pregnancy produce large quantities of colostrum and milk. Colostrum produced from cows given Se and VE is suitable to feed newborn calves and to be stored for later use. Improvement of Se status in calves born to cows given Se and VE in late pregnancy is not beneficial to passive immunity and growth.

Production of active bovine tracheal antimicrobial peptide in milk of transgenic mice

Tracheal antimicrobial peptide (TAP) is a member of the beta-defensin family of antibiotic peptides found in the tracheal mucosa of the cow. TAP gene expression in the bovine airway is inducible by lipopolysaccharide and inflammatory mediators, suggesting that it functions to protect the upper airway from infection. Limited availability of bovine TAP (bTAP) has precluded investigation of its potential utility in agriculture and medicine. To overcome this problem, transgenic mice expressing bTAP using an expression vector driven by control sequences from the murine whey acidic protein (WAP) gene have been generated. The WAP/bTAP transcript was detected in RNA isolated from mammary tissue of transgenic females. bTAP was purified to homogeneity from milk via acid precipitation, reverse-phase HPLC, and ion-exchange chromatography. This milk-derived bTAP had antimicrobial activity against Escherichia coli. Amino-terminal peptide sequencing confirmed the identity of this material as a bTAP isoform. bTAP available from a mammary gland bioreactor will allow evaluation of bTAP for use as an antibiotic in agriculture and medicine.

Cadmium uptake by Caco-2 cells. Effect of some milk components

The effect of some milk components on the cellular uptake of cadmium has been studied using a human intestinal cell line (Caco-2). Cadmium uptake by Caco-2 cells increased with the concentration of this metal in the culture medium, in a saturable way. These cells were exposed to different concentrations of cadmium and the synthesis of metallothionein was studied by a cadmium-saturation method. The levels of metallothionein increased with the cadmium concentration in the medium up to 20 microM of metal. Supplementation of the culture medium with 10% bovine milk caused a 25% decrease in the uptake of cadmium with respect to that internalized by the cells maintained in the culture medium alone. However, the uptake of cadmium from the medium supplemented with 10% human milk was similar to that with serum-free medium. beta-Lactoglobulin interacted with cadmium when studied by equilibrium dialysis, showing a stoichiometric binding constant of 5 x 10(4) l/mol. Interaction of lactoferrin with cadmium, however, was negligible. When Caco-2 cells were incubated in culture medium containing lactoferrin, cadmium uptake decreased with respect to that observed incubating the cells in a medium containing beta-lactoglobulin or in the free-protein medium. The inhibitory effect of lactoferrin on the uptake of cadmium might be due to a reduction of the cell surface charge, through its binding to the membrane.

Effects of vitamin E on mammary and blood leukocyte function, with emphasis on chemotaxis, in periparturient dairy cows

OBJECTIVE

To determine the effect of vitamin E supplementation on the immune system of dairy cows.

DESIGN

The following immune parameters were followed: production of chemotactic factors and superoxide by mammary macrophages and chemotactic responsiveness of blood neutrophils.

ANIMALS

16 healthy Holstein dairy cows.

PROCEDURE

Dairy cows were assigned to 1 of 2 experimental groups: control (no vitamin E supplementation) and vitamin E supplemented. Supplementation of vitamin E started 4 weeks before and continued up to 8 weeks after parturition, and included oral supplementation of vitamin E at the rate of 3,000 IU/cow/d. In addition, the same group of cows received 1 injection of vitamin E (5,000 IU) 1 week prior to the expected date of parturition. Blood samples were collected weekly throughout the experimental period.

RESULTS

Vitamin E supplementation enhanced by 30 to 83% (P < 0.05) chemotactic responsiveness of blood neutrophils beginning 2 weeks before to 4 weeks after parturition, compared with controls. There were no differences in production of superoxide or chemotactic factors by mammary macrophages between control and vitamin E-supplemented cows.

CONCLUSIONS

Vitamin E supplementation prevents the periparturient inhibition of neutrophil chemotaxis. It is unlikely that vitamin E affects directly the function of mammary macrophages.

Role of milk fractions, serum, and divalent cations in protection of mammary epithelial cells of cows against damage by Staphylococcus aureus toxins

OBJECTIVE

To determine the effect of milk and blood serum constituents on cytotoxicity of Staphylococcus aureus on mammary epithelial cells.

DESIGN

In vitro incubation of cells with cytotoxic agents and milk and serum constituents.

SAMPLE POPULATION

Mammary cells, milk, and blood obtained from 3 cows.

PROCEDURE

Staphylococcal alpha-toxin and culture supernatants from S aureus M60 and an alpha-toxin-negative mutant of M60 were incubated with bovine mammary epithelial cells in the presence of milk fractions, serum, and divalent cations. Propidium iodide fluorescence was used as a measure of cell damage.

RESULTS

Skim milk and milk whey inhibited S aureus cytotoxic agents. Skim milk protected against alpha-toxin damage to a greater extent than milk whey. Serum from an adult animal was more protective than was fetal serum. Milk fat and serum albumin had no protective effect. Divalent calcium and Mg2+ were more effective inhibitors of mammary epithelial cell damage caused by alpha-toxin than of damage attributable to M60 culture supernatant. Divalent calcium and Mg2+ at concentrations similar to those of free Ca2+ and Mg2+ in normal bovine milk decreased cytotoxic damage attributable to alpha-toxin. However, concentrations similar to those of total Ca2+ and Mg2+ in normal milk were required to decrease cell damage caused by M60 culture supernatant. The alpha-toxin-negative mutant was less cytotoxic than the M60 parent strain.

CONCLUSIONS

Casein, as well as Ca2+ and Mg2+ in bovine milk, inhibit the cytotoxic effect of S aureus on mammary epithelial cells.

Modulation of proliferation, second messenger levels, and morphotype expression of the rat intestinal epithelial cell line IEC-6 by fermented milk

Trophic effects of milk fermented with Lactobacillus helveticus, Lactobacillus paracasei ssp. paracasei, Bifidobacterium sp., or the combination of Lactobacillus bulgaricus and Streptococcus thermophilus (yogurt) were studied on the IEC-6 intestinal epithelial cell line. Incorporation of [methyl-3H]thymidine, mitochondrial dehydrogenase activities, cyclic AMP production, and differentiation of levels of the IEC-6 strain were evaluated between the 15th and 30th passage in culture. All fermented and unfermented milks enhanced trophic responses of IEC-6 cells in a dose-dependent manner. Compared with the corresponding milks, supernatant fractions were more effective in stimulating mitochondrial dehydrogenase response. Fermented milk supernatants were also more effective than the corresponding unfermented fractions. Increases in DNA synthesis and cyclic AMP confirmed the activation observed with mitochondrial dehydrogenase. Yogurt induced the more trophic response with an increased number of the more differentiated cell morphotype. Fermentation with L. casei also demonstrated an important trophic adaptation of IEC-6 cells. Milk processing by lactic acid bacteria enhanced trophic and proliferation responses of intestinal epithelial cell line IEC-6. These results suggested that IEC-6 cells could represent an accurate and easy in vitro model for testing the trophic quality of various nutrients and for an optimization of physiological digestive functions.

Detection of clinical mastitis by changes in electrical conductivity of foremilk before visible changes in milk

Mastitis was induced by the direct infusion of Staphylococcus aureus or Streptococcus uberis into the mammary gland of lactating cows. Changes in electrical conductivity of foremilk indicated the establishment of bacteria, increased SCC, increased clotting of milk, and, hence, disease, in advance of visible changes in the milk that could be diagnosed by a herdsperson. Clinical mastitis was detectable by changes in electrical conductivity of foremilk, 90% of cases were detectable when clots first appeared in foremilk, and 55% of cases were detectable up to 2 milkings prior to the appearance of clots. All subclinical infections from Staph. aureus were detected, but subclinical infections from Strep. uberis were not detected. The results suggested that clinical mastitis caused by these two major pathogens could be detected earlier by measuring changes in electrical conductivity of milk than by waiting for a herdsperson to detect visible changes in milk. Earlier detection would permit earlier treatment. However, the handheld sensor used in this experiment is impractical for commercial application, and reliable automated sensors and decision-making algorithms are required.

Does the male reproductive performance depend on the early lactation milk in rats?

This study investigated the role of the early lactation milk (ELM) on the male reproductive performance and the participation of GnRH on this effect in Wistar rats. Newborn males were divided into three experimental groups: 1) ELM-deprived pups, 2) ELM-deprived pups treated with exogenous GnRH 1, 7, 25, and 31 h after birth, and 3) non-ELM-deprived and without exogenous GnRH. In relation to the other two groups, the ELM-deprived male rats exhibited as adults: reduced fertility, decreased weight of both vas deferens and seminal vesicle, and reduced levels of fructose in the seminal vesicle and prostate gland. We suggest that the intake of ELM during the neonatal period is important to the later sexual development of rats, and that GnRH is somehow involved in such an effect.

The effect of mammary gland expression of human lysozyme on the properties of milk from transgenic mice

Transgenic mice were used as model systems to evaluate the impact of human lysozyme expression in the mammary gland. We previously generated two lines of transgenic mice that express human lysozyme mRNA in the mammary gland under the tissue-specific and developmentally correct control of the bovine gene promoter for alpha s1-casein. Concentrations of human lysozyme protein in milk of transgenic mice varied from .25 to .71 micrograms/microliters of milk. Human lysozyme secreted into mouse milk retained its antimicrobial activity, as determined by a denaturing polyacrylamide gel activity assay. The physical and functional properties of the milk were also altered, because mouse milk containing human lysozyme had a 35% decrease in rennet clotting time, a smaller median micelle size (157 nm vs. 172 nm), and a 2.5- to 3-fold greater gel strength than control milk. From these results, we conclude that the use of transgenic animals producing lysozyme in the milk is feasible and potentially useful to the dairy industry.

Nutrient-independent and nutrient-dependent factors stimulate protein synthesis in colostrum-fed newborn pigs

We hypothesized that nonnutrient components, including growth factors, present in colostrum contribute to the stimulation of protein synthesis in colostrum-fed neonatal pigs. We studied neonatal pigs fed mature milk, colostrum, or a formula containing a macronutrient composition comparable to that of colostrum for 24 h. We measured the circulating concentrations of insulin, insulin-like growth factor I, glucose, and amino acids at intervals throughout the 24-h period, after which we measured in vivo protein synthesis using a flooding dose of [3H]phenylalanine. The rates of protein synthesis in several tissues measured after 24 h of feeding were greater than those we reported previously after 6 h of feeding. The acute (within 6 h) stimulation of protein synthesis in visceral and skeletal muscle tissues of neonatal pigs fed milk, colostrum, or formula was primarily influenced by nutrient intake and associated with rapid secretion of insulin. Indirect evidence suggests that intestinal absorption of ingested colostral insulin was minimal. However, the sustained increase in tissue protein synthesis between 6 and 24 h coincided with an increase in circulating insulin-like growth factor I. We found a novel, specific stimulation of skeletal muscle and jejunal protein synthesis in colostrum-fed pigs that can be attributed to some nonnutrient component of colostrum.

Involution of mouse mammary glands in whole organ culture: a model for studying programmed cell death

The DNA fragmentation and gene expression patterns of involuting mouse mammary glands were compared to mammary glands in whole organ culture induced to involute by the withdrawal of lactogenic hormones. Non-random DNA degradation was observed both in vivo and in vitro, indicating that the withdrawal of lactogenic hormones triggers a program of epithelial cell death. Similar patterns of gene expression for the milk protein beta-casein and the apoptosis associated factors TGF-beta 1, TGF-beta 2 and TGF-beta 3 were observed in vivo and in vitro. These results indicate that the withdrawal of lactogenic hormones is responsible for decreased milk synthesis, epithelial cell death and tissue restructuring and that whole organ culture of mouse mammary glands is a useful model for studying the molecular events involved in these processes during involution.

Effects of milk and food on the absorption of enoxacin

The effects of milk and a standard breakfast on the oral absorption of enoxacin were evaluated in eight healthy volunteers in a randomized, balanced, four-way crossover study. After an overnight fast, 400 mg enoxacin was given with water, milk, a breakfast or with a breakfast and milk. The extent of enoxacin absorption was not affected by any of the three treatments, and no statistically significant changes were found with respect to peak plasma enoxacin concentration or time to peak. We conclude that enoxacin can be taken together with food and dairy products.

Use of HT-29, a cultured human colon cancer cell line, to study the effect of fermented milks on colon cancer cell growth and differentiation

Epidemiological and in vivo and in vitro experimental studies have suggested that fermented milks may interfere with the emergence and/or the development of colon cancer. The results, however, remain inconclusive. This prompted us to develop a new approach based on the use of HT-29, a cultured human colon cancer cell line, to study at the cellular level the effect of fermented milks on colon cancer cell growth and differentiation characteristics. Undifferentiated HT-29 cells have been grown in the continuous presence of milks fermented by one of the following bacterial populations: Lactobacillus helveticus, Bifidobacterium, L.acidophilus or a mix of Streptococcus thermophilus and L. bulgaricus. Penicillin G was added to the cell culture medium, resulting in a complete blockade of bacterial growth without significant effect on bacterial viability. One out of the four bacteria species studied, namely L.acidophilus, was without effect on both cell growth and differentiation. The three other bacterial strains induced a significant, although variable, reduction in the growth rate of HT-29 cells, which resulted in a 10-50% decrease in the cell number at steady-state (i.e. at cell confluency). The most efficient strains in lowering the HT-29 growth rate were L. helveticus and Bifidobacterium. Concomitantly, the specific activities of dipeptidyl peptidase IV (DPP IV), a sensitive and specific marker of HT-29 cell differentiation, and that of three other brush border enzymes (sucrase, aminopeptidase N and alkaline phosphatase) were significantly increased, thus suggesting that these cells may have entered a differentiation process. Altogether, these results indicate that the use of cultured colon cancer cells may be a useful tool to further study the effect of fermented milks on colon cancer and that bacterial strains may exert a different and specific effect on cancer cell growth and differentiation when used in fermented milk products.

Inhibitory effect of dairy products on the mutagenicities of chemicals and dietary mutagens

The antimutagenic effects of uninoculated milk and milks cultured with Bifidobacterium or Lactobacillus strains towards the mutagenicity induced by two direct mutagens, 4-nitroquinoline N-oxide and 2-nitrofluorene, and three dietary indirect mutagens, aflatoxin B1, benzo(a)pyrene and quercetin, were investigated using the in vitro Salmonella typhimurium test. Each cultured milk sample and control milk had a significant antimutagenic effect, to an extent varying with the mutagen used. Uninoculated milk had a greater inhibitory effect than cultured milks towards dietary indirect mutagens.