ABSORPTION OF ORALLY ADMINISTERED INSULIN BY THE NEWLY BORN CALF

Colostrum insulin supplementation does not influence immunoglobulin G absorption in neonatal Holstein bulls

Since insulin has been demonstrated to suppress IgG absorption in other neonatal species, we had the objective to delineate how colostral insulin concentrations affect IgG absorption in neonatal bovines. We enrolled Holstein bull calves (n = 48; body weight = 46.3 ± 0.84 kg) at birth and randomized them by birth order to receive (1) colostrum that contained basal insulin concentrations (12.9 μg/L; n = 16), or colostrum that had been supplemented with an exogenous insulin to increase the insulin concentration to either (2) 5 times (70.0 μg/L; n = 16) or (3) 10 times (149.7 μg/L; n = 16) that of the basal colostrum. Gross colostrum composition (crude fat: 4.1 ± 0.06%; crude protein: 11.7 ± 0.05%; lactose: 1.9 ± 0.01%; IgG: 63.9 ± 1.19 g/L) was similar between treatments and calves were fed (7% body weight, 3.1 ± 0.06 L) their treatments at 2, 14, and 26 h postnatal. Serum was collected at 0, 30, 60, 90, 120, 180, 240, 360, 480, and 600 min postprandial respective to the first and second colostrum feeding and analyzed for IgG concentration. The incremental area under the curve (I-AUC) and apparent efficiency of absorption (AEA) were calculated for the 10-h periods following the first and second colostrum meal. Serum IgG concentrations over time, I-AUC, and AEA were statistically analyzed as a complete randomized design. Colostrum insulin concentration did not affect serum IgG concentrations or the I-AUC or AEA after calves were fed colostrum at 2 and 14 h postnatal. High colostral insulin content is not detrimental or promotive to IgG absorption in neonatal Holstein bulls.

Colostrum insulin supplementation to neonatal Holstein bulls affects small intestinal histomorphology, mRNA expression, and enzymatic activity with minor influences on peripheral metabolism

The objectives of this study were to evaluate how varying colostral insulin concentrations influenced small intestinal development and peripheral metabolism in neonatal Holstein bulls. Insulin was supplemented to approximately 5× (70.0 μg/L; n = 16) or 10× (149.7 μg/L; n = 16) the basal colostrum insulin (12.9 μg/L; BI, n = 16) concentration to maintain equivalent macronutrient intake (crude fat: 4.1 ± 0.06%; crude protein: 11.7 ± 0.05%; and lactose: 1.9 ± 0.01%) among treatments. Colostrum was fed at 2, 14, and 26 h postnatal and blood metabolites and insulin concentration were measured at 0, 30, 60, 90, 120, 180, 240, 360, 480, and 600 min postprandial respective to the first and second colostrum meal. At 30 h postnatal, a subset of calves (n = 8/treatment) were killed to excise the gastrointestinal and visceral tissues. Gastrointestinal and visceral gross morphology and dry matter and small intestinal histomorphology, gene expression, and carbohydrase activity were assessed. Insulin supplementation tended to linearly reduce the glucose clearance rate following the first meal, whereas after the second meal, supplementation linearly increased the rate of glucose absorption and nonesterified fatty acid clearance rate, decreased the time to maximum glucose concentrations, and decreased the time to reach minimum nonesterified fatty acid concentrations. Additionally, insulin clearance rate was linearly increased by insulin supplementation following the second colostrum feeding. However, there were no overall differences between treatments in the concentrations of glucose, nonesterified fatty acids, or insulin in plasma or serum. With respect to macroscopic intestinal development, dry rumen tissue mass linearly decreased when insulin was supplemented in colostrum, and supplementation linearly increased duodenal dry tissue density (g dry matter/cm) while tending to increase duodenal dry tissue weight. Increasing the colostrum insulin concentration improved small intestinal histomorphological development in the distal small intestine, as ileal villi height and mucosal-serosal surface area index were increased by supplementing insulin. Lactase enzymatic activity linearly increased in the proximal jejunum while ileal isomaltase activity linearly decreased with insulin supplementation. These data indicate that changes in colostrum insulin concentrations rapidly affect gastrointestinal growth prioritization and carbohydrase activity. The changes in gastrointestinal ontology result in minor changes in postprandial metabolite availability and clearance.

Evaluation of a point-of-care meter for measuring glucose concentrations in dairy calves: A diagnostic accuracy study

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We validated a human glucose meter for measuring blood glucose of neonatal calves using 1,303 samples of plasma and 476 samples of whole blood.

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For plasma, hypoglycemia was established at a threshold of <4.45 mmol/L (sensitivity, 94.2%; specificity, 91.2%).

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For whole blood, hypoglycemia was established at a threshold of 4.95 mmol/L (sensitivity, 95.6%; specificity of 80.3%).

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The meter can measure glycemic status in calves and may be useful for treatment decisions on farm.

The objective of this cross-sectional, diagnostic accuracy study was to validate a human blood glucose meter (Contour Next One Meter, Ascensia Diabetes Care) for accuracy and precision when measuring blood glucose, and for diagnostic accuracy for hypoglycemic status in dairy calves using whole blood and blood plasma. A total of 49 male dairy calves [body weight (BW): 46.3 ± 0.8 kg] had jugular catheters placed within 75 min after birth. Thereafter, blood was withdrawn from the catheter at specific time points (−10, 10, 20, 30, 45, 60, 90, 120, 180, 240, 360, 480, and 600 min) relative to the first and second colostrum feedings (2 h 15 min and 14 h 5 min postnatal; feeding rate: 7% of BW wt/wt). The reference standard method for plasma glucose concentration was determined colorimetrically and in duplicate using the glucose oxidase-peroxidase reaction. Data were assessed for agreement between the glucose meter and the reference standard using Lin's concordance correlation coefficients (CCC), coefficients of determination (precision), and Bland-Altman plots. In addition, a mixed linear regression model was built using the reference method as the outcome, with the glucose meter and repeated measures of time as the explanatory variables and calf as a random effect. The sensitivity (Se), specificity (Sp), and area under the curve (AUC) for the glucose meter using calf whole-blood and plasma were calculated at a threshold of <4.44 mmol/L to determine hypoglycemia. The precision (CCC = 0.95, R² = 0.93) and accuracy (AUC = 0.98) of the glucose meter were very high when used on 1,303 blood plasma samples. Youden's index revealed a threshold of <4.45 mmol/L for the glucose meter when used with plasma, leading to Se of 94.2% and Sp of 91.9%, with 92.5% of samples being correctly classified, suggesting high diagnostic accuracy. When using whole blood, precision (CCC = 0.85 and R² = 0.73) and accuracy (AUC = 0.92) were high when used on 476 samples. Youden's index revealed a threshold of <4.95 mmol/L for the glucose meter when used with whole calf blood, leading to Se of 95.6% and Sp of 80.3%, with 84.7% of samples being correctly classified, suggesting high diagnostic accuracy for use on farm. In summary, this glucose meter was validated for measuring calf blood glucose using both plasma and whole blood. This meter can measure glycemic status in calves and may be useful for clinical and on-farm use to make intervention decisions.

Effects of colostrum management on transfer of passive immunity and the potential role of colostral bioactive components on neonatal calf development and metabolism

Neonatal dairy and beef calves are required to ingest adequate volumes of high-quality colostrum during their first hours of life to acquire transfer of passive immunity (TPI). As such, immunoglobulin G (IgG) has largely been the focus of colostrum research over recent decades. Yet, little is known about the additional bioactive compounds in colostrum that potentially influence newborn calf development and metabolism. The purpose of this narrative review is to synthesize research regarding the effects of colostrum management practices on TPI, as well as to address the potential role of additional colostral bioactive molecules, including oligosaccharides, fatty acids, insulin, and insulin-like growth factor-I, in promoting calf development and metabolism. Due to the importance of IgG in ensuring calf immunity and health, we review past research describing the process of colostrogenesis and dam factors influencing the concentrations of IgG in an effort to maximize TPI. We also address the transfer of additional bioactive compounds in colostrum and prepartum management and dam factors that influence their concentrations. Finally, we highlight key areas of future research for the scientific community to pursue to ultimately improve the health and welfare of neonatal dairy calves.

Glucagon-like peptide 2 (GLP-2) in bovine colostrum and transition milk

Bovine colostrum contains growth factors, cytokines, hormones, and enzymes, which have important roles in stimulating gastrointestinal development of neonatal calves. In the present study, we measured the concentration of glucagon-like peptide 2 (GLP-2), one of the gut-derived peptides secreted from intestinal L-cells, in colostrum and transition milk of Japanese black cattle. All colostrum samples were collected within 24 h after calving (d 0) and transition milk was collected at 24, 48 and 72 h relative to the time at colostrum sampling (d 1, d 2 and d 3, respectively). Concentrations of GLP-2 in colostrum were 5.53 ± 1.07 ng/mL on average (range = 0.94–9.60 ng/mL) and decreased from d 0 to 3 (P < 0.01). Furthermore, concentrations of GLP-2 in colostrum and transition milk were quadratically decreased with the elapsed time from parturition until colostrum sampling (R² = 0.48, P < 0.01). Our results show for the first time that GLP-2 is present in bovine colostrum and transition milk and that concentrations decreased with elapsed time from parturition.

Feeding colostrum or a 1:1 colostrum:whole milk mixture for 3 days after birth increases serum immunoglobulin G and apparent immunoglobulin G persistency in Holstein bulls

Conflicting reports exist on whether prolonged IgG consumption can further increase serum IgG in neonatal calves. Given that higher serum IgG in neonates has lifelong benefits, our objective was to determine whether serum IgG can be increased by providing multiple meals containing IgG to neonatal calves. Twenty-seven Holstein bulls were all fed 1 colostrum meal (7.5% body weight; 62 g of IgG/L) at 2 h after birth and randomly assigned to be fed (5% body weight) colostrum (COL; n = 9), whole milk (WM; n = 9), or a 1:1 colostrum:whole milk mixture (MX; n = 9) every 12 h from 12 to 72 h. Serum IgG was measured at 1, 2, 3, 6, 9, 11, and 12 h after birth. After the 12-h meal, IgG was determined at 0.5-h intervals until 16 h and then at 1-h intervals from 16 to 24 h. Serum IgG was then measured at 27 h, then every 6 h from 30 to 60 h. From 60 to 64 h, IgG was measured every 0.5 h, then at 65 and 66 h, and then every 2 h until 72 h. Serum IgG increased rapidly between 2 and 12 h for all calves. A treatment × time interaction occurred as serum IgG began to diverge between treatments after they were fed at 12 h; the interaction was greatest over the entire period for COL compared with both MX and WM and was greater for MX than for WM. Maximum IgG concentrations (C_max) were 30.4 ± 0.8, 27.2 ± 0.8, and 23.9 ± 0.8 g/L for COL, MX, and WM, respectively. Although MX C_max was equivalent to both COL and WM C_max, COL C_max was greater than WM C_max. Feeding COL and MX also prolonged the time to reach C_max. Respectively, these calves achieved C_max at 29.5 and 27.0 ± 3.4 h, whereas WM IgG peaked at 13.4 ± 3.4 h. No differences were observed for apparent efficiency of absorption between treatments from 0 to 12 h and 0 to 24 h. Immunoglobulin G area under the curve (AUC) was the same for COL and MX calves over the entire experimental period and from when treatments were fed. The IgG AUC for 0 to 72 h for WM calves was 27.4% lesser than that for COL calves but not different from MX calves. However, the IgG AUC for 12 to 72 h for WM calves differed relative to that for both COL (30.8% less) and MX (19.6% less) calves. Serum IgG concentrations were more persistent when COL (88.2 ± 2.4%) and MX (91.2 ± 2.4%) were fed rather than WM (75.3 ± 2.4%). Prolonged IgG consumption increased serum IgG concentrations, corresponding to the mass of IgG fed, and improved apparent IgG persistency in Holstein bulls. Neonatal calves should be fed at least 62 g of IgG at 12 h after birth to further increase serum IgG concentrations.

Epigenetic programming of porcine endometrial function and the lactocrine hypothesis

Epigenetic programs controlling development of the female reproductive tract (FRT) are influenced by the effects of naturally occurring bioactive agents on patterns of gene expression in FRT tissues during organizationally critical periods of foetal and perinatal life. Aberrations in such important cellular and molecular events, as may occur with exposure to natural or manmade steroid or peptide receptor-modulating agents, disrupt the developmental program and can change the developmental trajectory of FRT tissues, including the endometrium, with lasting consequences. In the pig, as in other mammals, maternal programming of FRT development begins pre-natally and is completed post-natally, when maternal effects on development can be communicated via signals transmitted in milk. Studies involving relaxin (RLX), a prototypic milk-borne morphoregulatory factor (MbF), serve as the basis for ongoing efforts to identify maternal programming events that affect uterine and cervical tissues in the neonatal pig. Data support the lactocrine hypothesis for delivery of MbFs to neonates as a specific consequence of nursing. Components of a maternally driven lactocrine mechanism for RLX-mediated signalling in neonatal FRT tissues, including evidence that milk-borne RLX is delivered into the neonatal circulation where it can act on RLX receptor (RXFP1)-positive neonatal tissues to affect their development, are in place in the pig. The fact that all newborn mammals drink milk extends the timeframe of maternal influence on neonatal development across many species. Thus, lactocrine transmission of milk-borne developmental signals is an element of the maternal epigenetic programming equation that deserves further study.

Effects of peroral insulin and glucose on circulating insulin-like growth factor-1, its binding proteins and thyroid hormones in neonatal calves

There is disagreement in the literature about the ability of neonatal calves to absorb perorally administered insulin. This study evaluated the absorption of a bolus of insulin administered alone or with an energy souce and its effects on the circulating insulin-like growth factor system and thyroid hormones in newborn Holstein-Friesian calves. Within 1 h of dosing, mean serum insulin and triiodothyronine (T3) concentrations had increased considerably, whether the insulin was applied alone (n = 4) or together with glucose (n = 4), accompanied by marked hypoglycemia. No significant changes were observed in control calves (n = 4) given the vehicle solution. Increased serum glucose and T3 concentrations with no change in insulinemia occurred in a 4th group of calves given glucose alone. At 32 h of age and after 3 meals of colostrum there were no differences in glycemia, insulinemia, or proteinemia among the 4 groups of calves examined. Mean serum insulin-like growth factor-I (IGF-I) tended to decrease over this period in the control group. The decrease was more pronounced in the insulin-treated group but absent in both groups that received glucose. These differences were associated with equivalent differences in abundance of the 40-45K IGF-binding protein-3 (IGFBP-3); however, lower molecular mass IGFBPs were not affected. The results show that a pharmacological peroral dose of insulin can lead to rapid systemic alterations in the IGF/IGFBP system in neonatal calves that can be modified by simultaneous administration of a small energy supply in the form of glucose.

Gastrointestinal tract as a target organ for orally administered insulin

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

Dietary insulin affects leucine aminopeptidase, growth hormone, insulin-like growth factor I and insulin receptors in the intestinal mucosa of neonatal pigs

BACKGROUND

Recent studies suggest that milk-borne insulin may regulate the development of the gastrointestinal tract in neonatal mammals.

OBJECTIVES

To explore the mechanism by which milk-borne insulin affects gastrointestinal tract development, we examined the effect of dietary insulin on the expression levels of leucine aminopeptidase (LAP) and insulin-like growth factor I (IGF-I), as well as its effect on growth hormone (GH), IGF-I and insulin receptors in the small intestinal mucosa of neonatal pigs.

METHODS

Five piglets were anesthetized and sampled within 2-4 h after birth. They were not allowed to suckle and were used as newborn controls (group N). Ten other piglets from 5 litters were randomly divided into group M (n=5), which was fed cow's milk, and group MI (n=5), which was fed cow's milk and insulin (2.5 mg/l). Piglets in groups M and MI were artificially fed for 3 days and then sampled. Total RNA in their intestinal mucosa was extracted with Tripure reagents (Roche, USA). Reverse transcription PCR (RT-PCR) was used to semi-quantify mRNA levels of target genes and 18S rRNA was used in an RT-PCR system as an internal control. PCR products were loaded onto a 9% nondenaturing polyacrylamide gel. The gel was stained by silver staining agents. Digital photos were taken and the strength of the band areas was quantified using software.

RESULTS

The results showed that the DNA contents and LAP activity in the small intestines of the piglets in group MI were higher (p<0.05) than in the piglets in group N. Compared with group M, piglets in group MI exhibited significantly increased expression levels of both insulin and GH receptor in the ileum, and LAP in the jejunum (p<0.05); IGF-I receptor expression levels in both the jejunum and ileum were significantly decreased (p<0.01 and p<0.05, respectively), while IGF-I expression was unchanged (p>0.05).

CONCLUSION

Collectively, dietary insulin increased mRNA levels of insulin and GH receptor, which could help explain the effect of dietary insulin on receptor-mediated postnatal development of the small intestine. Dietary insulin suppressed IGF-I receptor expression, which may be the result of negative feedback caused when insulin binds to IGF-I receptors.

Intestinal and systemic effects of oral insulin supplementation in rats after weaning

Oral insulin has intestinal trophic effects in suckling animals. In mice, lower glucose and lipid levels may be seen when oral insulin is given after the weaning period. The purpose of the present study is to examine local and systemic effects of oral insulin supplementation in rats in the postweaning period. Immediately after weaning, Sprague-Dawley rats received either drinking water (controls) or oral insulin in their drinking water (1 U/ml) for either 1 week or 6 weeks. Intestinal mucosal parameters (bowel and mucosal weight, mucosal DNA and protein) and histological changes were examined in all study groups. Glucose levels were monitored weekly, and at the end of the study, blood levels of glucose, lipids, and insulin were measured in the fasting state. After 1 week of insulin supplementation, mucosal weight in duodenum and jejunum as well as jejunal DNA content were significantly higher in insulin-supplemented rats compared to controls. Duodenal circumference and villus height in jejunum were significantly higher in insulin-supplemented rats compared to controls on both day 7 and day 42. Total cholesterol levels were significantly lower in the study group compared with the controls. We conclude that oral insulin supplementation exerts intestinal trophic effects, as well as systemic effects in the postweaning period in rats.

Influence of co-administration of oral insulin and docosahexaenoic acid in mice

Insulin and docosahexaenoic acid are both present in human milk. The aim of this study was to examine the effect of co-administration of oral insulin and DHA in mice. Immediately after weaning, Balb C mice were divided into four groups of seven mice each for a period of 4 weeks. Group 1 received a chow diet only. Group 2 received a chow diet and also was given human insulin (1 unit/mL of drinking water) without docosahexaenoic acid. Group 3 received a chow diet supplemented with docosahexaenoic acid (500 mg/kg/day in the chow) and no insulin. Group 4 received a chow diet and supplementation with both human insulin and docosahexaenoic acid. At 28 days, fasting blood levels of glucose, insulin, lipids, lipid peroxidation analysis, docosahexaenoic acid plasma levels, and docosahexaenoic acid content in red blood cells were determined. We found that glucose levels were lower in the group that was supplemented with insulin only (group 2, 61.4 mg/dL +/- 2.8,mean +/- SD) and in the group that was supplemented with DHA only (group 3, 61.1 mg/dL +/- 2.0) compared to controls (group 1, 71 mg/dL +/- 6.9, P < 0.0001). Supplementation of both insulin and docosahexaenoic acid (group 4) resulted in significantly lower glucose levels (56.4 mg/dL +/- 2.6) compared to those in groups 2 and 3 (P < 0.01). No significant differences were found in lipid profile or lipid peroxidation between the groups. We conclude that adding insulin or docosahexaenoic acid to the diet of weaned Balb C mice reduces glucose blood levels. Supplementation with both substances has a synergistic effect. The presence of insulin and docosahexaenoic acid in human milk may be the cause for reduced glucose levels in breast-fed infants, in addition to the known effects of DHA on insulin sensitivity.

Relation of beta-casomorphin to apnea in sudden infant death syndrome

Sudden infant death syndrome (SIDS) is the most common cause of death in infants and its pathogenesis is complex and multifactorial. The aim of this review is to summarize recent novel findings regarding the possible association of beta-casomorphin (beta-CM) to apnea in SIDS, which has not been widely appreciated by pediatricians and scientists. beta-CM is an exogenous bioactive peptide derived from casein, a major protein in milk and milk products, which has opioid activity. Mechanistically, circulation of this peptide into the infant's immature central nervous system might inhibit the respiratory center in the brainstem leading to apnea and death. This paper will review the possible relationship between beta-CM and SIDS in the context of passage of beta-CM through the gastrointestinal tract and the blood-brain barrier (BBB), permeability of the BBB to peptides in infants, and characterization of the casomorphin system in the brain.

Insulin in human milk: postpartum changes and effect of gestational age

OBJECTIVE

To determine if human milk insulin (HMI) concentrations are affected by gestational age and postnatal age.

DESIGN AND SETTING

An observational study carried out in a level III neonatal intensive care unit. Insulin concentrations were determined in human milk of 90 parturient mothers who delivered between 30 and 41 weeks gestation. Samples were collected on days 3 and 10 after delivery.

RESULTS

HMI concentrations for mothers of preterm infants were not significantly different from those of full term infants, on either day 3 or 10 post partum. When results for all 90 mothers were pooled, regardless of gestational age, HMI concentration fell significantly from day 3 to day 10 (50.1 (34.6) v 41.1 (28.5) microU/ml; p = 0.01; mean (SD)). However, this decrease was only significant for mothers delivering at term (37-41 weeks).

CONCLUSIONS

HMI concentrations were not influenced by gestational age at delivery. They decreased post partum, mainly in mothers of term infants. The postnatal changes in HMI concentrations and the effects of oral insulin on the immature intestinal mucosa warrant further investigation.

Insulin in human milk and the prevention of type 1 diabetes

Although controversial, exclusive breast milk feeding was shown to exert a protective effect in preventing type 1 diabetes. In contrast, an early introduction of cow's milk-based formula in young infants may enhance the risk of disease, especially in genetically susceptible children, presumably by an increase of intestinal permeability to macromolecules such as bovine serum albumin and beta-casein, which may arouse autoimmunity. We have shown that human milk contains insulin in substantial concentrations, while insulin is barely detectable (if at all) in infant formulas. Orally administered insulin was demonstrated to promote gut maturation and to reduce intestinal permeability to macromolecules. Furthermore, oral insulin may induce tolerance to insulin and protect against the development of type 1 diabetes. We herewith raise a hypothesis that human milk is protective against the development of type 1 diabetes by virtue of the effects of its substantial content of insulin.

Gastrointestinal stability and absorption of insulin in suckling pigs

Stability and absorption of orally administered fluorescein-isothiocyanate labeled insulin (FITC-insulin) in the gastrointestinal (GI) tract were investigated in newborn and 3-day-old pigs. The uptake of FITC-insulin by the intestinal epithelial cells was visualized using confocal laser scanning microscopy. Following oral administration, 3 h later 56 and 88% of orally administered fluorescence was found in the GI tract in newborn and 3-day-old piglets, respectively. Chromatographic analysis revealed that 15-37% of fluorescence recovered from the gastric and proximal intestinal contents was eluted in the void volume of a Sephadex G-25 column. It was also observed that oral administration of FITC-insulin at a dose of 100 nmol/kg body weight led to a significant decrease in blood glucose in newborn pigs (P<0. 05) but not in 3-day-old pigs. Microscopic examination showed that FITC-insulin was taken up via the vesicular transport mechanism throughout the whole small intestine but the ileum appeared to be a preferred site for FITC-insulin transport in newborn pigs. In 3-day-old pigs, the uptake of FITC-insulin occurred only in the distal part of the small intestine. These findings suggest that milk-borne insulin may partially survive in the GI lumen and subsequently act on the gastrointestinal tract in suckling piglets, while GI absorption of milk-borne insulin is limited to newborn pigs.

Crucial role of milk-borne insulin in the development of pancreatic amylase at the onset of weaning in rats

The development of pancreatic amylase activity was examined in rats fed in regular cages or in special cages, designed so the pups could not reach solid food to prevent weaning. In both groups, the amylase activity in zymogen granules increased in rat pups aged 14 days, peaked at 18 days, and thereafter remained at a 1.6-fold higher level than at 14 days of age. An increase in the plasma concentration of immunoreactive insulin preceded the increase of amylase activity, whereas the plasma concentration of C-peptide, indicating the secretion rate of endogenous insulin, remained unchanged. The administration of insulin at 20 ng/ml (the physiological concentration) in the milk formula caused an increase in the plasma insulin concentration of 17-day-old pups. In addition, increased pancreatic amylase activity was observed in 17-day-old rats raised on milk formula to which insulin was added. We propose that the increase of amylase activity at the beginning of weaning is dependent on the milk-borne insulin and not on the dietary change in rats.

Effect of PSK and its subfractions on peripheral blood lymphocytes mediated cytotoxicity against urinary bladder tumor cells

Our previous studies have indicated that the protein-bound polysaccharide Kreha (PSK) enhances the cytotoxic activity of peripheral blood lymphocytes (PBL) against the T24 human urinary bladder tumor cell line in patients with bladder tumor. Since PSK consists of a mixture of various kinds of protein-bound polysaccharides, the present study was designed to examine which subfractions of PSK mediated the enhancement of cytotoxicity. When PSK was separated according to size, treatment of PBL with the 50 kilodalton (kd) or less fraction killed T24 cells more efficiently than unfractionated PSK-treated PBL. The higher molecular weight fractions did not enhance killing above the control level. PSK was fractionated on a diethylaminoethyl (DEAE)-cellulose column to obtain a protein rich fraction that absorbed onto the column and a polysaccharide rich fraction that did not. PBL treated with the polysaccharide rich fraction were able to kill T24 cells more effectively than unfractionated PSK-treated PBL. The protein rich fraction had no effect on the killing. Further fractionation of the polysaccharide rich fraction was performed by differential precipitation with ammonium sulfate. PBL treated with the precipitated fraction at 70-80% saturation (PSK Fraction D) enhanced cytotoxicity equal to that of the polysaccharide rich fraction. Treatment of PBL with the other fractions did not augment the cytotoxicity. These enhancement by PSK fractions were observed in healthy donors and also in patients with bladder tumor. An increase of the proliferative response of PBL to PSK Fraction D as well as unfractionated PSK was observed. Treatment of PBL with PSK Fraction D had no effect on the proportion of PBL binding to T24 cells, thus suggesting a post-binding effect. The structure of PSK Fraction D as inferred from the results of methylation analysis was mainly an alpha-glucan. These results demonstrate that PSK mediated enhancement of cytotoxicity and proliferation of PBL may be largely due to an alpha-glucan of less than 50 kd.

Changes in concentrations of insulin-like growth factor 1, insulin and growth hormone in bovine mammary gland secretion ante and post partum

Concentrations of insulin-like growth factor 1 (IGF-1), insulin and growth hormone were measured in the secretion of the bovine mammary gland from day 70 ante partum until 6 d post partum. Highest levels were found during the last 2 weeks ante partum followed by a rapid decrease during the first milkings post partum. The association of IGF-1 with its binding proteins in milk was analysed and striking differences were found in the distribution of bound and free IGF-1. IGF-1 appeared mainly in the bound form (91%) at days 40-2 ante partum. Free IGF-1 preponderated in the first milkings post partum (73%) and changed again to about 85% in the bound form after day 4 post partum. A slightly acidic pH (6.3) of the secretion was correlated with high amounts of free IGF-1. Gel filtration experiments revealed a possible pH-dependent mechanism for the binding of IGF-1 to its binding proteins in milk.

Biologically active peptides in the gastrointestinal lumen

The release of a variety of biologically active peptides into the gastrointestinal lumen via gastric, duodenal and intestinal secretions, as well as in the saliva, pancreatic juice and bile, has been explored. The key features of luminal secretion of peptides such as secretion at high concentrations, neurohormonal regulation, luminal orientation of stimulated secretion, stability of peptides in the gastrointestinal lumen, altered secretion under pathophysiological conditions, and biological activity of luminally administered peptides are discussed. This review develops a detailed picture of the current understanding of luminal secretion of peptides and their possible biological functions under normal and pathophysiological conditions.

Lactational variation and relationship to postnatal growth of insulin-like growth factor-I in mammary secretions from genetically diverse sows

Mammary secretions obtained from four groups of sows at parturition and on days 7, 14 and 21 of lactation were defatted and assayed for total protein and insulin-like growth factor-I (IGF-I). Sows (n = 57) represented two breeds (Landrace and Duroc) and two genetic lines (selected for differences in sow productivity index, SPI) within each breed. Colostrum of Duroc sows was 4-6 fold and 30-60 fold greater in protein (P less than .001) and IGF-I (P less than .001) concentrations, respectively, than the corresponding day 7 milk from these sows. In contrast, the colostrum of Landrace sows was 2-3 fold and 30-50 fold greater in protein (P less than .001) and IGF-I (P less than .001) concentrations, respectively, than the corresponding day 7 milk. The IGF-I content in milk from Duroc sows did not differ among days 7, 14 and 21 of lactation, whereas the IGF-I content of day 7 milk from Landrace sows exceeded those for the corresponding 14 day and 21 day secretion (P less than .05). IGF-I concentration in days 14 and 21 milk was higher in Duroc (P less than .001 respectively) than Landrace sows. No significant differences in total protein or IGF-I content of mammary secretions were observed between the selected and control lines within each breed.(ABSTRACT TRUNCATED AT 250 WORDS)

Receptor mechanisms of the neonatal intestine and their relationship to immunoglobulin absorption and disease

Immunoglobulin absorption by the calf has been the subject of considerable research. Despite these efforts little is known about the cytological events that occur at the level of the intestinal epithelial cell. These events have been studied extensively and characterized in the laboratory rodent; however, there have been few attempts to make corollaries between the two species. All neonatal animals display certain similarities in their intestinal morphology that may be correlated, with immunoglobulin absorption. Selectivity in absorption appears to be variable among neonatal animal species; however, all demonstrate some selectivity. Selectivity in absorption implies that receptors are a necessary component in the transport of immunoglobulins. Selectivity further requires binding of immunoglobulins to an endocytic vesicle membrane to ensure transport through the cell, circumvention of intracellular digestion, and release at the basolateral cell membrane. A decrease of immunoglobulin absorption may be accomplished in a variety of ways such as competition between intestinal microbes and immunoglobulins for a common receptor on the intestinal epithelial cell. An additional consideration is aberrant synthesis or recycling of the cell membrane receptor, as induced by metabolic decelerators such as cortisol. Failure to recycle immunoglobulin receptors also would decrease efficiency of absorption.

The relationship between the insulin content and inhibitory effects of bovine colostrum on protein breakdown in cultured cells

Protein Degradation in ten mammalian cell lines is markedly inhibited by small amounts of bovine colostrum. This response is consistent with the growth-promoting activity of colostrum that has been reported previously. Fractionation of colostrum on DEAE cellulose showed that most of the inhibitory activity against protein breakdown on H35 cells coeluted with insulin. Insulin concentrations in different batches of bovine colostrum ranged from 0.67 nM to 5.7 nM, approximately 100-fold higher than in blood. The sensitivity of protein breakdown in H35 or MH1C1 hepatoma lines to these colostrum samples was proportional to their insulin concentrations and could largely be accounted for by the amount of insulin present. Removal of insulin from colostrum by means of a protein A-anti-insulin antibody affinity column was accompanied by a loss of the ability of colostrum to inhibit protein breakdown in H35 or MH1C1 cells. However, in IMR90 fibroblasts, a cell line with a similar sensitivity to colostrum as the two hepatomas but very insensitive to insulin, protein breakdown was still inhibited by the insulin-free colostrum. These results suggest that, whereas the effect of bovine colostrum in H35 or MH1C1 cells is actually a response to insulin, different growth factors in colostrum account for the inhibition of protein breakdown in other cell lines.

The immune response in hepatic cirrhosis: animal and human studies

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The influence of specific chemical factors in the solvent on the absorption of macromolecular substances from the small intestine of the new-born calf

1. The absorption, without change, of [(131)I] and [(125)I]solutes of high molecular weight after duodenal infusion has been measured in anaesthetized calves less than 20 hr old by analysis of lymph collected from the thoracic or intestinal duct.2. Factors present in boiled bovine colostrum whey known to be necessary for the rapid absorption of [(131)I]bovine serum gamma-globulin have now been shown to accelerate the passage of [(131)I]polyvinyl pyrrolidone (PVP) of mean mol. wt. 160,000 (K.60) into the lymph in a comparable manner.3. [(131)I]PVP K.30 (mean mol. wt. 40,000) and [(131)I]human serum albumin could be absorbed to some degree in the absence of solvent factors necessary for the absorption of solutes of higher mol. wt. and a large proportion of the solute thus absorbed passed directly into the portal capillaries.4. Lactate and pyruvate and salts of certain lower volatile fatty acids resemble factors in colostrum whey in their facilitation of the absorption of both gamma-globulin and PVP K.60: these active compounds were not however found in colostrum in significant quantities.5. Potassium isobutyrate was the most effective of the compounds tested and at concentrations of 56.7 m-mole/l. generally accelerated absorption to a greater degree than did colostrum whey itself.6. Absorption of both gamma-globulin and PVP K.60 from colostrum whey was characterized by a profuse flow of lymph containing relatively low concentrations of labelled solute. In contrast, when these solutes were fed in solutions containing simple compounds such as potassium isobutyrate they appeared in very high concentrations in the lymph, the flow of which remained relatively scant.7. When [(125)I]PVP was administered in water, little was absorbed. If, however, such an infusion was followed 3 hr later by a duodenal infusion of colostrum, [(125)I]PVP passed into the lymph almost immediately. This response was too rapid for the colostrum to have reached the absorbing cells in the terminal ileum.8. Intravenous infusions of L+lactate have been found to facilitate the absorption of [(125)I]PVP K.60 introduced into the duodenum in water. This indicates that some of the solvent factors which accelerate absorption may reach the terminal ileum via the blood vascular system after they themselves have been absorbed from the upper small intestine.

BIOPHYSICAL AND IMMUNOLOGICAL STUDIES ON BOVINE IMMUNE GLOBULINS WITH EVIDENCE FOR SELECTIVE TRANSPORT WITHIN THE MAMMARY GLAND FROM MATERNAL PLASMA TO COLOSTRUM

Three immune globulins in maternal serum and colostrum and newly born calf serum, have been characterized and compared. An examination was made to determine first, which of the maternal serum immune globulins accumulate in the circulation of the calf and secondly, the selectivity of the mammary gland for these proteins compared with the intestinal mucosa of the newly born calf.

By difference in their electrophoretic mobilities three antigenically related immune globulins were isolated from bovine serum.

The immune lactoglobulins in bovine colostrum were qualitatively similar to those in serum. However, marked differences were observed between the relative concentrations in serum and colostrum of the three immune globulins.

An electrophoretically fast immune globulin (C1), present in colostrum at high concentration, was shown to be antigenically similar to an immune globulin (S1) present in the maternal serum at low concentration.

These findings indicate that the mammary gland showed a highly selective preference for, and hence ability to concentrate in, colostrum, the electrophoretically fastest serum immune globulin.

The slowest serum immune globulin and the component with intermediate electrophoretic mobility (S3 and S2 respectively) were both present at high concentration in bovine maternal serum, but were transmitted at different rates into the colostrum, so that the slowest serum immune globulin (S3) was present in the colostrum as a comparatively minor component (C3).

In contrast to the mammary gland, the intestine of the newly born calf (permeable to undegraded protein during the first 24 hours of life) showed no selectivity. Immune globulins showing the three electrophoretic mobilities were absorbed equally readily.

Thus, while the bovine mammary gland showed a highly selective preference for certain electrophoretically different serum proteins, no comparable selectivity was shown by the intestinal mucosa of the newly born calf.

The results emphasize the heterogeneity of bovine immune globulins and show that the calf receives into its circulation from ingested colostrum selected maternal serum immune globulins. This selection of proteins from maternal plasma, for admission to the calf's circulation, occurs within the mammary gland during the formation of colostrum but not during absorption across the calf's intestinal mucosa.