Heterogeneity of the kappa-casein glycomacropeptide and physiological activity of its fractions

A number of fractions with differing intensity of the inhibitory action on the gastric secretion were obtained by gel filtration in a column with biogels P-30 and P-2 of cappa-casein glycomacropeptide. A low-molecular fraction displays the greatest capacity for inhibiting gastric secretion. Desialism, heating and partial hydrolysis of glycomacropeptide with pepsin, trypsin and chemotrypsin used separately have no effect on its inhibitory activity. The resulting data suggest that the inhibitory action of glycomacropeptide is caused by a certain part rather than by entire molecule.     

Influence of bovine mastitis on lipolysis ond proteolysis in milk

Lipolysis and proteolysis in milk were determined before, during, and after experimentally induced mastitis. Streptococcus agalactiae was infused into one quarter of five cows to elicit an infection. Milk protease activity was higher during infection, but milk lipase activity was unchanged. Lipolytic damage to milk fat and proteolytic damage to milk casein occurred in the udder prior to milking during an infection. Lipolysis increased due to increased susceptibility of the milk fat to lipase action during infection. The mechanism of the increased susceptibility of the fat to lipolysis was not determined. After infections were eliminated, SCC, initial and stored FFA concentrations, and initial tryosine values returned to preinfection levels. However, after infections were eliminated, milk protease activity as determined by an increase in tryosine values remained elevated as milk SCC returned to preinfection levels. Protease activity returned to preinfection levels within 10 d after SCC returned to preinfection levels.     

Opioid peptides derived from in-vitro proteolysis of bovine whey proteins

The formation of opioid peptides by in-vitro proteolysis of whey proteins was investigated. Bovine β-lactoglobulin (β-LG) or -lactalbumin (-LA) were predigested with pepsin and subsequently treated with either trypsin (Try) or trypsin+chymotrypsin (Try+Chy). For separation and identification of the peptides. HPLC chromatography, protein sequencing and amino acid analysis were used. Identified peptides were synthesized by Peninsula Laboratories Europe Ltd. UK. Binding to rat brain homogenates was tested against ³H-naloxone. The effects of the peptides on smooth muscle were tested in coaxially stimulated guinea pig ileum in vitro. Digestion of β-LG with pepsin plus Try, or Try+Chy yielded Tyr-Leu-Leu-Phe (β-lactorphin). Proteolysis of -LA with pepsin alone produced Tyr-Gly-Leu-Phe (-lactorphin) although a higher degree of hydrolysis was achieved by addition of Try. Among hydrolysates of whey proteins at least -lactorphin exerted a weak but continuous opioid property both in terms of receptor binding and smooth muscle effects.     

Glycopeptide obtained from k-casein and its effect on protein assimilation

The products of restricted proteolysis of kappa-casein were separated by gel filtration. Intravenous injection of high- and low-molecular fractions substantially reduced the pentagastrin-stimulated acid secretion in the anesthetized rat stomach. Intermediate fractions had lesser physiological activity. One of the active fractions administered intraintestinally inhibited acid secretion and reduced the pentagastrin-stimulated secretion in rat weanling isolated stomach. All the active fractions inhibited the stimulated secretion in rats with a ligated vagus. It is concluded that the nervous system does not play a crucial role in the mechanism by which gastric acid secretion is inhibited by the products of restricted proteolysis of kappa-casein. Decreasing acid secretion in the stomach, glycopeptide provides for the conditions favouring the efficacy of protein utilization at an early age. It is suggested that the effect of glycopeptide obtained from kappa-casein on the process of assimilation is mediated via peptide hormones.     

花生四烯酸的生理活性及其应用

花生四烯酸是一种长链不饱和脂肪酸 ,具有营养、保健和医疗功能。本文介绍了花生四烯酸的代谢途径及功能特性的研究概况及其应用。     

Kinetics of changes in plasmin activity and proteolysis on heating milk

Heat-induced inactivation of bovine plasmin, denaturation of beta-lactoglobulin (beta-lg), the interactions between both species and casein micelles and the subsequent net effect on proteolysis of beta-casein was studied in a model system consisting of phosphocasein and beta-lg in synthetic milk ultrafiltrate. The inactivation of plasmin and denaturation of beta-lg were first order reactions, with the rate of inactivation of plasmin being greater than the rate of denaturation of beta-lg. The predominant mechanism involved in the denaturation of plasmin in the temperature range 65-80 degrees C was its interaction with beta-lg (kr at 60 degrees C, 0.0526; Ea, 176 KJ/mol). At the point of complete inactivation of plasmin approximately 45% of the beta-lg remained undenatured. Thermal inactivation of plasmin through other mechanisms was negligible. The association of beta-lg with the casein micelles at 60 degrees C had a rate constant of 3.71 x 10-5 min-1 and an Ea of 259 KJ/mol; thermal denaturation of beta-lg was of much less importance, with a rate constant at 60 degrees C of the order of 1 x 10-10 min-1 and an Ea of 250 KJ/mol. On denaturation of all beta-lg in the system, a maximum of approximately 55% was associated with the casein micelles. The effect of heating on the subsequent hydrolysis of beta-casein indicated that the level of plasmin activity was the most important factor affecting proteolysis, while the interaction of beta-lg with the casein micelles had limited effect. Overall, thermal stability of plasmin in milk is very much dependent upon its interaction with beta-lg.     

共轭亚油酸的生理功能及提高其在乳制品中含量的途径

概述共轭亚油酸(CLA)的生理功能,及提高其在乳制品中CLA的途径,如选育高产CLA的动物品种、研发新饲料、控制和改进加工条件等.     

牛初乳制品功能性成分的分析

利用牛初乳中的免疫球蛋白活性因子，开发具有独特生理功能的乳制品成为牛初乳利用的热点。本研究利用十二烷基硫酸钠-聚丙烯酰胺电泳法和酶联免疫吸附法对市售的牛初孔制品的质量进行了分析与评价。结果表明，目前牛初乳制品的蛋白含量与组成有很大的差异，并且活性免疫球蛋白含量较低。目前牛初乳制品存在的问题亟待解决，市场亟待规范。     

牛初乳加工工艺及开发研究进展

在分析影响牛初乳营养成分稳定性的各因素基础上,综述了目前的牛初乳及其制品加工工艺以及各种方法的特点,尤其是牛初乳杀茵工艺,以供生产实践参考.     

Effects of yeast expressed recombinant interleukin-2 and interferon-gamma on physiological changes in bovine mammary glands and on bactericidal activity of neutrophils

The physiological effects of intramammary infusions of recombinant bovine cytokines in six lactating dairy cows on the quality and yield of milk and the bactericidal activity of milk neutrophils were investigated. Recombinant bovine interleukin-2 (rboIL-2) and interferon-gamma (rboIFN-gamma) were produced in the yeast Pichia pastoris. Two animals were given rboIL-2 (2 x 10(5) units) in two quarters, two animals were given rboIFN-gamma (6.5 x 10(5) units) in two quarters, and the other two cows received a dose of rboIL-2 in one quarter and rboIFN-gamma in a second quarter. In addition, each animal was given phosphate-buffered saline (PBS) in the other two quarters as a control. Somatic cell counts and conductivity of the fore milk were monitored before and after infusion. Neutrophils were isolated from quarter milk samples 36 h after infusion of cytokine or PBS and their bactericidal activities against Staphylococcus aureus were measured in vitro with a colorimetric assay. Quarters infused with rboIL-2 or rboIFN-gamma showed significant but transitory increases in both milk somatic cell counts and conductivity when compared with preinfusion values and with control quarters. There were minimal effects on daily milk yield. Neutrophils isolated from milk from quarters infused with rboIL-2 showed enhanced bactericidal activity against Staph. aureus. The bacterial killing from rboIL-2 treated quarters was significantly greater, with a mean of 63.5% compared with a mean of 5.4% for neutrophils taken from uninfected quarters to which PBS had been administered. The bactericidal activities for quarters treated with rboIFN-gamma and infected quarters treated with PBS were 15.0 and 30.0% respectively. The results indicate that intramammary infusions of rboIL-2 and rboIFN-gamma to lactating cows are well tolerated, and that rboIL-2 can activate milk neutrophils and augment their bactericidal activity.     

天然食用色素的结构与生理活性分析

概述了天然食用色素的结构和主要性质、不同抗氧化机理及最新的生理学研究进展,为功能性天然食用色素的开发和应用提供了参考。     

Bioactive peptides with ACE-I and antioxidant activity produced from milk proteolysis

In this study, milk was hydrolyzed using protease (Asperigillus oryzae), trypsin, pepsin, or papain at concentrations of 0.001, 0.005, or 0.01 g/100 g milk for 30 or 60 min to produce angiotensin-converting enzyme inhibitory and antioxidant peptides. Results showed that the proteolysis, antioxidant, and ACE-I activity gradually increased with the increase in the enzyme concentration and hydrolysis time. The protease-treated milk had the highest proteolytic and ACE-I activity, while the papain-treated milk had the lowest. The papain-treated milk exhibited the greatest Fe²⁺ chelating activity. The use of trypsin at concentration of 0.001 g/100 g milk for 60 min produced ACE-I and antioxidant activity without changes in the technological properties of milk.     

Contribution of macrophages to proteolysis and plasmin activity in ewe bulk milk

A total of 225 bulk sheep milk samples were collected from 5 intensively managed flocks during early, mid, and late lactation to assess the contribution of macrophages to the regulation of the plasmin-plasminogen system. Samples were analyzed for composition, somatic cell counts, milk renneting characteristics, and for plasmin (PL), plasminogen (PG), and plasminogen activators (PA) activities. Isolation of macrophages from milk was performed using a magnetic positive separation and mouse antiovine macrophage antibody; separated cells were lysed by several freeze-thaw cycles, and activity of urokinase PA (u-PA) was determined. Plasmin activity decreased during lactation (42.06 ± 0.66, early; 31.29 ± 0.66, mid; 28.19 ± 0.66 U/mL, late). The reduction in PL activity recorded in the mid and late lactation milk matched the increase in PG:PL ratio. The activity of PA increased throughout lactation; the highest value being recorded in the late lactation milk (260.20 ± 8.66 U/mL). Counts of isolated and concentrated macrophages were higher in early and mid lactation milk (3.89 ± 0.08 and 3.98 ± 0.08 log₁₀ cells/mL, respectively) than in late lactation milk (3.42 ± 0.08 log₁₀ cells/mL). Stage of lactation did not influence the activity of u-PA detected in isolated macrophages. The activity of u-PA associated with isolated milk macrophages only minimally contributed to total PA activity detected in milk. Proteolytic enzymes, associated with isolated macrophages, act on α-casein hydrolysis, as shown by urea-PAGE electrophoresis analysis. Somatic cell counts did not exceed 600,000 cells/mL, and this threshold can be considered a good index of health status of the flock and of the ability of milk to being processed. Our results lend support to the hypothesis that macrophages in ewe bulk milk from healthy flocks only slightly contribute to the activation of the PL-PG system.     

Hormones in bovine milk and milk products: A survey

A survey of the published data on the occurrence of hormones in milk and milk products is presented. Bovine milk and colostrum contain a large number of hormones from either steroidic or peptidic origin. The main categories to which these molecules belong are gonadal (estrogens, progesterone, androgens), adrenal (glucocorticoids), pituitary (prolactin, growth hormone) and hypothalamic hormones (GRH, LH-RH, TRH). Other molecules, such as proteins related to the parathyroid hormone, insulin, somatostatin, calcitonin, bombesin, erythropoeitin and melatonin, are also of interest. The exact role of hormones in the development of the newborn is still not known, but it is believed that they may contribute to the growth of the newborn and to the development and maturation of its gastrointestinal and immune systems.     

The nutritional and physiological impact of cereal products in human nutrition.

There is a need for reeducation of the population, especially in developed countries, as to the value of cereals in the diet. Cereals provide calories and important nutrients to the diet. Refined cereal products and unrefined cereals have certain advantages and disadvantages. With refinement, some nutrients and fiber are removed, but the body is better able to make use of certain nutrients. Essential nutrients are being replaced through fortification to compensate for losses in processing. The high fiber content of unrefined cereal products is believed to aid in the prevention of certain diseases. Special dietary bakery products have been introduced for the treatment of conditions generally exacerbated by standard food items. The increased consumption of cereal products appears warranted as a means of decreasing the saturated fat and cholesterol consumption. Cereals and cereal products have been mentioned in connection with allergies, celiac disease, schizophrenia, obesity, dental caries, cancer, atherosclerosis, goiter, and diverticulosis. This review discusses the possible role of cereals in the prevention or cause of these health problems.     

木瓜蛋白酶水解鱼蛋白酶解产物抗氧化活性研究

研究了鱼蛋白酶解产物的抗氧化能力,通过单因素和正交试验,得到酶反应的最佳工艺条件为底物浓度15%、加酶量5%、水解pH 7、水解时间3.0 h、温度为50℃。在此条件下鱼蛋白水解产物抗氧化活性较好,其DPPH 清除率为68.38%。     

口服牛初乳生理功效的最新研究进展

综述了口服牛初乳最新功能性试验，包括对人体消化道、上呼吸道、组织缓冲系统、人体皮肤的生理效应及其作为运动员营养补剂的应用效果。     

Immunosuppressive activity of bovine seminal plasma on bovine lymphocytes in vitro

Pooled seminal plasma obtained from six bulls was tested for its immunosuppressive activities in vitro on blastogenesis of bovine lymphocytes. Lymphocyte stimulation assay and mixed lymphocyte reaction were used as test procedures. Concanavalin A and phytohemagglutinin were utilized in the lymphocyte stimulation assays as nonspecific stimuli. Tritiated thymidine uptake by the lymphocytes was measured after incubation for 5 d with seminal plasma. Undiluted seminal plasma was cytotoxic to lymphocytes up to and at 1/100 dilution but not at 1/400. Undiluted seminal plasma was immunosuppressive at a 1/400 dilution. Lyophilization of seminal plasma without prior dialysis resulted in loss of immunosuppressive activity. After dialysis and lyophilization, the reconstituted seminal plasma suppressed thymidine uptake by Concanavalin A and phytohemagglutinin-stimulated bovine lymphocytes while being noncytotoxic. This paper documents that bovine seminal plasma is immunosuppressive and also cytotoxic to the bovine cells that generate an immune response.