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PubMed1995

Improvement of hyperlipidemia and proteinuria without noticeable growth retardation by feeding a methionine and threonine supplemented low-casein diet to nephritic rats.

We have previously demonstrated that low-casein diets supplemented with cystine and threonine reduced hyperlipidemia and proteinuria in nephritic rats without noticeable protein malnutrition. In the present study, we examined whether or not a low-casein diet supplemented with methionine, sulfur amino acid other than cystine, and threonine would ameliorate the symptoms without protein malnutrition in rats with nephrotoxic serum nephritis by feeding experimental diets for 10 days. A methionine-threonine-supplemented 8.5% casein diet (8.5 CMT), when compared with a basal 20% casein diet, improved hypoalbuminemia as well as hyperlipidemia and proteinuria without noticeable growth retardation and fatty liver induction in nephritic rats. Fecal bile acid excretion and microsomal cholesterol 7 alpha-hydroxylase activity were enhanced by 8.5CMT feeding. These results suggest that amino acid-balanced low protein diet would have a beneficial effect on the symptoms of nephritis. They also suggest that the hypocholesterolemic action of 8.5CMT may be, at least in part, due to increased fecal bile acid excretion accompanied by elevated microsomal cholesterol 7 alpha-hydroxylase activity.

Animals↗
PubMed2001

Orotic acid added to casein, but not to egg protein, soy protein, or wheat gluten diets increases 1,2-diacylglycerol levels and lowers superoxide dismutase activities in rat liver.

Effects of the dietary addition of orotic acid to a diet containing casein as a sole protein source on lipid levels in the liver and serum, activities of antioxidant enzymes in the liver, and some enzyme activities in serum, were compared with other diets containing egg protein, soy protein, or wheat gluten, respectively. 1. The contents in the liver of each lipid were increased by the addition of orotic acid as compared with those values without it. The orotic acid added to the casein diet caused accumulation of more liver total lipids, triacylglycerol, 1,2-diacylglycerol, and phospholipids than those fed three other diets. 2. The addition of orotic acid to the casein, but not to the other three diets, lowered the activities of liver superoxide dismutase and increased the activities of both serum ornithine carbamoyltransferase and alanine aminotransferase. Thus, the significant increase in serum ornithine carbamoyltransferase activities as the marker of liver lesions may result from the marked accumulation of liver lipids, decreased activities of hepatic superoxide dismutase, and the increased level of hepatic 1,2-diacylglycerol, followed by possibly the increased level of superoxide anion and increased activity of protein kinase C in rats fed the casein diet with orotic acid added.

Alanine Transaminase↗
PubMed2002

Casein digestion by Debaryomyces hansenii isolated from cheese.

To understand the possible proteolytic contribution of yeast during cheese ripening, Debaryomyces hansenii 212 was isolated from commercial blue-veined cheese and incubated in a medium containing casein. Growth and casein degradation were recognized at the cheese-ripening temperature. Proteolytic activity was found in the intracellular fraction, and the enzyme, which was attached to the cell wall, primarily acted on beta-casein. The cytosol contained more than 90% of the total proteolytic activity which was responsible for the degradation of both alpha(s)- and beta-casein. These results suggest that the contribution of yeast to cheese ripening would depend on the susceptibility to cell lysis in addition to its proteolytic activity.

Caseins↗
PubMed2003

Stimulatory effect of a dietary casein phosphopeptide preparation on the mucosal IgA response of mice to orally ingested lipopolysaccharide from Salmonella typhimurium.

The effect on immunoglobulin production of a commercially available casein phosphopeptide preparation (CPP-III) consisting mainly of bovine alpha s2-casein (1-32) and beta-casein (1-28) in mice that had orally ingested lipopolysaccharide (LPS) from Salmonella typhimurium was investigated. No significant difference in body weight gain was observed between the mice fed on the CPP-III-added diet and those fed on the control diet. The mice fed on the CPP-III-added diet exhibited similar serum and intestinal IgG, IgM, and IgE responses towards LPS to those fed on the control diet. In contrast, fecal and intestinal anti-LPS IgA and total IgA in mice fed on the CPP-III-added diet were significantly higher than in those fed on the control diet. Spleen cells from mice fed on the CPP-III-added diet produced larger amounts of IgA, IL-5, and IL-6 than cells from mice fed on the control diet. These results suggest that dietary casein phosphopeptide may protect a host from invasion of the intestinal mucosa by food-born pathogenic microorganisms.

Adjuvants, Immunologic↗
PubMed1981

Casein kinase in cytosol of rat and mouse mammary epithelial cells isolated from histone kinase by MgCl2 treatment and influence of pregnancy and lactation on the enzyme activity.

Rat mammary glands contain cyclic AMP-independent casein kinase and cyclic AMP-dependent histone kinase. The former was easily isolated from cyclic AMP-dependent histone kinase by MgCl2 treatment. Mammary casein kinase was not activated by cyclic nucleotides, and Mg++ and ATP were required for activation. The specific activity of casein kinase in cytosol of rat mammary epithelial cells increased 2 to 3-fold during pregnancy and lactation. Cytosol of mouse mammary epithelial cells also contained cyclic AMP-independent casein kinase, and the activity of this enzyme was about three times that of the Golgi fraction.

Animals↗
PubMed2006

Effects on production traits of haplotypes among casein genes in Norwegian goats and evidence for a site of preferential recombination.

In goat milk the most abundant proteins are the casein genes, CSN1S1, CSN2, CSN1S2, and CSN3. Mutations have been identified within these genes affecting the level of gene expression, and effects on milk production traits have been reported. The aim of this study was to detect polymorphisms (SNPs) in the casein genes of Norwegian goats, resolve haplotype structures within the loci, and assess the effect of these haplotypes on milk production traits. Four hundred thirty-six Norwegian bucks were genotyped for 39 polymorphic sites across the four loci. The numbers of unique haplotypes present in each locus were 10, 6, 4, and 8 for CSN1S1, CSN2, CSN1S2, and CSN3, respectively. The effects of the CSN1S1 haplotypes on protein percentage and fat kilograms were significant, as were the effects of CSN3 haplotypes on fat percentage and protein percentage. A deletion in exon 12 of CSN1S1, unique to the Norwegian goat population, explained the effects of CSN1S1 haplotypes on fat kilograms, but not protein percentage. Investigation of linkage disequilibrium between all possible pairs of SNPs revealed higher levels of linkage disequilbrium for SNP pairs within casein loci than for SNP pairs between casein loci, likely reflecting low levels of intragenic recombination. Further, there was evidence for a site of preferential recombination between CSN2 and CSN1S2. The value of the haplotypes for haplotype-assisted selection (HAS) is discussed.

Animals↗
PubMed1991

Toxicity and tissue accumulation of copper in chicks fed casein and soy-based diets.

Experiments were conducted to study Cu toxicity in chicks fed casein or soy-containing diets containing graded levels of excess CuSO4.5H2O. Differences between diets in measures of Cu toxicity were pronounced. Addition of 800 mg of Cu/kg to a casein-dextrose semipurified diet decreased weight gains by 63%, but the same addition of Cu to a corn-soybean meal complex diet decreased gains by only 8%. At all levels of Cu supplementation (100, 200, 400 or 800 mg/kg), Cu deposition in the liver was increased markedly in chicks fed casein diets compared with those fed the complex diet. Substituting soy-protein concentrate for casein in the semipurified diet resulted in a marked decrease in Cu toxicity as measured by weight gain reductions and tissue accumulation of Cu.

Animals↗
PubMed2003

Pancreatic exocrine secretion in steers infused postruminally with casein and cornstarch.

Our objective was to evaluate the effect of postruminal protein infusion on pancreatic exocrine secretions. One Holstein, two crossbred, and five Angus steers (305 +/- 5 kg) with pancreatic pouch-duodenal reentrant cannulas and abomasal infusion catheters were used in a replicated 4 x 4 Latin square. All steers were abomasally infused with 1,050 g/d of raw cornstarch with treatments of 0, 60, 120, or 180 g/d of sodium casein suspended in water to yield 6,000 g/d of infusate daily. Steers were limit-fed (1.5 x NEm; 12 equal portions daily) a 90% corn silage, 10% supplement diet formulated to contain 12.5% CP. Periods consisted of 3 d of adaptation to infusion, 7 d of full infusion, 1 d of collection, and 7 d of rest. Pancreatic juice was collected in 30-min fractions continuously for 6 h. Total juice secreted and the pH of individual fractions were recorded, a 10% subsample was retained to form a composite sample, and remaining fluid was returned to the duodenum. Juice composite samples were stored (-30 degrees C) until analyzed for total protein and activities of alpha-amylase, trypsin, and chymotrypsin. Casein infusion linearly increased alpha-amylase concentration (182 to 271 units/mL; P < 0.02; 17.5 to 24.6 units/mg of protein; P < 0.03) and secretion rate (26,847 to 41,894 units/h; P < 0.01). Total juice secretion (155 g/h), pH of pancreatic juice (8.13), secretion rate of protein (1,536 mg/h), and concentration of protein (10.2 mg/mL) in pancreatic secretions were not affected (P > 0.05) by casein infusion. Similarly, casein infusion did not change 0.05) trypsin and chymotrypsin concentrations (1,379 and 349 units/L or 0.134 and 0.033 units/mg of protein, respectively) or secretion rates (206 and 52 units/h, respectively). Abomasal infusion of protein with starch stimulated a greater pancreatic secretion of alpha-amylase activity into the intestine than infusion of starch alone.

Abomasum↗
PubMed2003

Influence of substrate and/or neurohormonal mimic on in vitro pancreatic enzyme release from calves postruminally infused with partially hydrolyzed starch and/or casein.

Our objectives were to determine the effects of neuroendocrine challenge and substrates on in vitro alpha-amylase and trypsin release in pancreatic tissue collected from Holstein calves (n = 24; 88 +/- 3 kg) abomasally infused for 10 d with tap water (control), partially hydrolyzed starch (SH; 4 g/[kg of BW x d]) and/ or casein (0.6 g/[kg of BW x d]). The caudal portion of the pancreas was removed, rinsed with ice-cold saline, cut into approximately 2 x 2-mm segments, and incubated in oxygenated Krebs Ringer bicarbonate buffer containing no substrate (control), glucose, amino acids, or VFA at 39 degrees C. After 60 min of incubation, neurohormonal mimics (none; control), carbachol (acetylcholine analog; 10 microM final), or caerulein (cholecystokinin mimic; 100 nM final) were added to the flasks and tissue was incubated for 60 min. Pancreatic tissue concentrations and in vitro release of alpha-amylase and trypsin decreased (P < 0.001) in calves abomasally infused with SH. Carbachol increased (P < 0.10) alpha-amylase and trypsin release in tissue collected from all calves. An effect of caerulein to increase alpha-amylase release (P < 0.10) was only observed with prior exposure to abomasal casein infusion in vivo or with simultaneous incubation with amino acids in vitro. Caerulein increased (P < 0.10) trypsin release in tissue collected from all calves except for those receiving SH + casein. Glucose decreased (P < 0.10) alpha-amylase release from pancreatic tissue collected from calves receiving abomasal control and casein treatments. Amino acids decreased (P < 0.10) alpha-amylase and trypsin release from pancreatic tissue collected from calves receiving the abomasal control treatment. Glucose, amino acids, and VFA decreased (P < 0.10) trypsin release from tissue collected from calves receiving abomasal SH. These data indicate that carbachol can stimulate pancreatic enzyme release in vitro. Caerulein, however, is only effective in stimulating in vitro pancreatic enzyme release in tissue from calves with an increased postruminal protein supply or in tissue incubated with amino acids. The results indicate that postruminal and local nutrients might be important in altering the responsiveness to a neuroendocrine challenge and could be an important regulatory event involved with dietary adaptation in ruminants.

Abomasum↗
PubMed1999

Molecular surface sequence analysis of several E. coli enzymes and implications for existence of casein kinase-2 bacterial predecessor.

Casein kinase-2 (CK2) is known as pleiotropic eukaryotic protein kinase that phosphorylates significant number of cellular proteins. Not all functions of the protein were registered up to the present time. However, it is known that this Ser/Thr-specific kinase is involved in the cell cycle progression and is essentially required for the eukaryotic cell viability. Fully automated molecular surface analysis procedure for identification of functionally significant surface residues and sequences on the base of protein spatial structure was elaborated. Using the elaborated procedure, several E. coli enzymes spatial structures and sequences were investigated. It was found that most of the casein kinase 2 potential sites found in sequences of enzymes are accessible for modification. Four of the 5 structures studied have CK2 consensus sites that may definitely influence the activity of the enzyme upon phosphorylation. Some of the potential "CK2-sites" has amino acid contents characteristic for physiological substrates of casein kinase 2 in eukaryotes. The main point of the elaborated method and the structural evidence for existence of a putative casein kinase E. coli predecessor or a protein with similar kinase activity are discussed. Physiological, biochemical, structural and evolutionary aspects of the existence of the putative predecessor are considered.

Adenylate Kinase↗
PubMed1992

Cloning and sequencing of human kappa-casein cDNA.

A cDNA encoding kappa-casein of human milk was cloned and sequenced. The kappa-casein cDNA was isolated from a lambda gt11 library generated from mRNA prepared from a mammary gland biopsy obtained from a lactating woman. The library was screened with polyclonal rabbit antibodies raised against purified native kappa-casein. The obtained nucleotide sequence contained an ORF sufficient to encode the entire amino acid sequence of a kappa-casein precursor protein consisting of 182 amino acids. This includes a tentative signal peptide of 20 amino acids and a processed protein of 162 amino acids.

Amino Acid Sequence↗
PubMed2000

Casein secretion and cytological differentiation in mammary tissue from bulls of high or low genetic merit.

We evaluated tissue content and secretion of milk proteins by mammary parenchymal explants prepared from tissue of mature Holstein bulls as a possible index for genetic merit. Explants from eight selection-line and eight control-line bulls were cultured for 48 or 96 h in medium with 5% fetal bovine serum with or without the addition of lactogenic hormones. Four selection-line and four control-line bulls were also treated for 7 d with estrogen and progesterone or placebo before tissue was removed on d 15 of the experiment. Overall, tissue content and secretion of casein were increased approximately twofold in selection-line bulls. Differences between genetic lines were evident only with the addition of lactogenic hormones. However, treatment of bulls with steroids was not necessary for casein secretion or detection of differences between genetic lines. Averaged for both lines, 96-h media concentrations of casein were 89-fold greater for explants cultured with added lactogenic hormones. Epithelial cells were classified as nonsecretory, droplet-containing, or degenerated. The appearance of droplet-containing cells was markedly increased in cultures supplemented with lactogenic hormones, and the cells were most often located within epithelial folds or pockets. Only occasionally did we observe areas of alveolar-like tissue. The data demonstrate that it is possible to induce the secretion of casein in mammary explants prepared from sexually mature bulls, that lactogenic hormones markedly stimulate secretion, and that differences in genetic merit may be expressed.

Amino Acids↗
PubMed2000

Proteolysis of alphas-casein as a marker of Grana Padano cheese ripening.

Since casein proteolysis has a critical role in defining the typical characteristics of Grana Padano cheese, we evaluated the hydrolysis of alphas-casein during the ripening process. Thanks to the high specificity of the anti-alphas((alphas1 + alphas2)-casein monoclonal antibody and amino acid sequence determination, it was possible to identify three main alphas-casein-derived polypeptides in cheese: alphaa, alphab, and alphac. Their production by the three enzymes most involved in cheese proteolysis (pepsin, chymosin, and plasmin) was evaluated by performing in vitro digestions. Data showed that alphaa was released in cheese mainly by the chymosin attack, while alphab and alphac were due to the action of plasmin. A significant correlation between the abundance of some polypeptides and ripening process was shown.

Amino Acid Sequence↗
PubMed2002

Growth kinetics and fractal dimensions of casein particles during acidification.

Small angle static light scattering was used to study the effect of milk dilution in permeate on the mechanism of acid-induced aggregation of casein particles. Growth kinetics of casein aggregates during acidification was characterized by the succession of four populations of particles. The first one corresponded to casein particles ranging from 0.1 to 1 microm, with a mean value of 0.3 microm. The second population, from 1 to 10 microm, was quickly replaced by a third population, from 10 to 100 microm, which gave rise to the last population measurable, from 100 to 1000 microm. The angular dependence of static light scattering from about 0.01 to 50 degrees was used to determine the fractal dimension (D) of pH-induced casein aggregates. With the formation of about 10-microm aggregates, fractal structures appeared. The D values, determined from double logarithmic plots of intensity versus scatteringvector resulted in values between 1.85 and 2.03.

Animals↗
PubMed2003

Effect of temperature and aggregation rate on the fractal dimension of renneted casein aggregates.

This study deals with the influence of chymosin/casein ratios and temperature on the fractal dimension of renneted casein aggregates in diluted milk. The angular dependence of static light scattering, from 50 to 110 degrees, was used to determine fractal dimension from double logarithmic plots of intensity versus scattering vector. No significant effect was observed when varying chymosin/casein ratios from 3.3 to 79.2 microg of chymosin/g of casein at 30 degrees C with a resultant fractal dimension value of 2.20. Temperature, on the other hand, influenced the aggregation mechanisms with fractal dimension values equaled to 2.32, 2.22, and 2.15 at 25, 30, and 35 degrees C, respectively, for a chymosin/casein ratio at 13.2 microg of chymosin/g of casein. The importance of hydrophobic interactions in fractal aggregation of renneted casein particles is discussed.

Animals↗
PubMed2006

Microfiltration of butter serum upon casein micelle destabilization.

The gross composition of butter serum, the aqueous phase of butter, is comparable to that of buttermilk, except that it has a higher content of material derived from the milk fat globule membrane (MFGM). As such, butter serum is a good source for further purification of MFGM material. The purified fraction could be of interest for its emulsifying and nutritional properties. The effect of sodium citrate and ethanol on the dissociation of butter serum casein micelles, and their effect on casein retention upon tangential microfiltration were investigated. Optimal conditions of casein micelle dissociation were assessed by using an experimental design (response surface full central composite orthogonal design) with temperature and ethanol or sodium citrate concentration as design variables and the Hunter L* value as response variable. For both dissociating agents, a highly significant reduced quadratic model was fit to the data. Microfiltration tests were performed on pure butter serum, and on butter serum in the presence of sodium citrate, under optimal dissociation conditions (50 degrees C, 80 mM). A cellulose acetate membrane with a pore size of 0.15 microm was used. From the filtration curves and fouling coefficients it was clear that the addition of sodium citrate improved the permeation flux, and minimized fouling. All fractions were analyzed for dry matter, protein, lactose, lipid, and polar lipid contents. The protein fraction was further characterized by sodium dodecyl sulfate-PAGE. It was shown that sodium citrate greatly enhanced casein transmission through the membrane, but at the expense of substantial losses of polar lipids.

Butter↗
PubMed2006

Activity and nature of plasminogen activators associated with the casein micelle.

In fresh milk, plasminogen, the zymogen form of plasmin (PL), is the predominant form. Therefore, plasminogen activators (PA) can contribute significantly to PL activity in milk. Both tissue-type PA (tPA) and urokinase-type PA (uPA) exist in milk; however, contradictory findings have been reported for which type of PA is most closely associated with the casein micelles. Little is known about the factors that might lead to variations in the individual activities of the PA. The objective of this work was therefore to investigate possible factors that might affect the association of tPA and uPA with the casein micelle and their activities thereafter. Plasminogen activators were isolated from milk samples with different somatic cell counts following 2 different isolation protocols. Determination of uPA, tPA, and PL activities was carried out quantitatively following chromogenic assays using 2 different substrates, and qualitatively using specialized sodium dodecyl sulfate-PAGE. Different isolation methods and conditions led to differences in uPA, tPA, and PL activities. Urokinase-type PA activity was significantly higher in PA fractions isolated from milk with high somatic cell counts than from milk with low somatic cell counts. Activity results indicated that in pasteurized milk uPA could dissociate from the somatic cells and bind to casein. Moreover, a high level of PL in isolated PA fractions contributed to significantly enhanced PA activities. Overall, results confirmed the association of both uPA and tPA with the casein micelle; however, their amounts, activities, and molecular weights varied based on the nature of the milk and methods of separation, with uPA being the PA with greater potential to affect plasminogen activation in milk.

Animals↗
PubMed1975

Structure and stability of casein micelles.

The structure and stability of casein micelles are determined in large measure by the amino acid sequences of the constituent alphas1-, beta-, and kappa- caseins. In this paper we review, and attempt to connect with sequence data where possible: (1) molecular weight, structure, and dissociation of casein micelles; (2) physical characteristics of monomeric caseins, especially the distrubition of charged and hydrophobic residues and the possible occurrence of helical regions; and (3) forces involved in association of monomers.

Amino Acid Sequence↗