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PubMed1978

Effect of reductive alkylation of the epsilon-amino group of lysyl redsidues of casein on its nutritive value in rats.

Casein epsilon-aminolysyl residues were converted to the methyl (and dimethyl), isopropyl or cyclopentyl derivatives in high yield with formaldehyde, acetone or cyclopentanone, respectively, in the presence of sodium borohydride. When incorporated into diets at 10% as the sole protein source, the chemically modified caseins failed to support growth of young rats. Methyl casein did, however, support limited growth after about 5 days. Plasma threonine levels increased and lysine levels decreased markedly in rats fed the alkyl caseins. The respective alkyllsine derivatives were present in plasma and urine. In another experiment, nearly normal or normal growth was obtained by feeding lysine-supplemented methyl or isopropyl casein, respectively. A preparation of partially methylated casein, containing approximately equal amounts of monomethyl- and dimethyllysines, supported normal rat growth. These results demonstrate that lysine deficiency was produced by feeding highly alkylated caseins. Digestibility of the chemically modified caseins in vivo was not affected, although in vitro studies with trypsin and alpha-chymotrypsin showed lowered digestibility. Since no apparent toxicity was observed limited methylation of food proteins may be useful for protection of lysyl residues against deteriorative reactions during processing and storage.

Acetone↗
PubMed1983

Correlation between the cholesterolemic responses produced by dietary cholesterol and casein in rabbits.

Rabbits were fed three semipurified diets, namely a cholesterol-free soy protein diet, a cholesterol-free casein diet or a diet containing soy protein plus cholesterol (2 g/kg). One group (Chol-Cas) of 24 rabbits was fed successively the diet containing soy protein plus cholesterol (25 days), the soy protein diet (36 days) and the casein diet (20 days). Another group (Cas-Chol) consisting of 25 animals received consecutively the diet containing casein, soy protein and soy protein supplemented with cholesterol. Hypercholesterolemia was induced by the diets containing cholesterol or casein, whereas regression was seen on the soy protein diet. Within the Chol-Cas or Cas-Chol group the cholesterolemic response to casein and that to cholesterol was significantly correlated, the correlation coefficient being as high as 0.66. This correlation was still observed when calculated for animals either hypo- or hyperresponsive to dietary casein or cholesterol. When all animals were pooled, the correlation coefficient for the cholesterolemic response to casein and to cholesterol was only 0.33. The mean response to dietary cholesterol and to casein was significantly higher in the last dietary period than in the first period.

Animals↗
PubMed1985

The effect of diet on retention by the rat of iron from a radiolabeled casein test meal.

Previous work has shown that weanling rats fed a soy protein isolate (SPI)-based diet retained less iron from a casein test meal than did rats fed a casein-based diet. In the present work this diet effect was further investigated. In experiment 1 rats were fed either SPI-or casein-based diet (about 25 ppm Fe) for 13 d, fasted overnight, given a 59Fe-labeled casein-based test meal, and refed either the same or the other diet for 7 d. 59Fe retention was determined by the percent of ingested label retained after 7 d. SPI reduced 59Fe retention when fed prior to the test meal (52.5 vs. 61.5%, P less than 0.001) and also when fed following the test meal (50.8 vs. 63.2%, P less than 0.001). In experiment 2a, exposure of SPI to steam at 108 degrees C for 30 min did not lessen the observed diet effect. In experiment 2b rats were fed either an SPI-or casein-based diet, and casein test meals were fed as above on days 14, 35 and 56. The SPI-based diet reduced 59Fe retention from the casein test meal fed on d 14 (58.2 vs. 68.0%, P less than 0.005), for the meal on d 35 there was no difference, and for the final test meal rats fed SPI retained more 59Fe (53.0 vs. 40.2%, P less than 0.01). In experiment 3 lactalbumin was shown to decrease 59Fe retention to the same extent as SPI (54.9 and 53.4%) as compared to casein (73.3%), whereas neither rapeseed protein concentrate (68.8%) nor oxalic acid (72.2%) had any significant adverse effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Plasma and brain ammonia and amino acids in rats measured after feeding 75% casein or 28% egg white.

Male rats were trained to consume their daily food intake in 3 h. When rats were fed 6% casein for 14 d and were then fed either the 6 or 75% casein diet for 1 d, the plasma and brain ammonia concentrations of rats fed 75% casein were higher (P less than 0.05) at 23 h after test meal initiation compared to those of rats fed 6% casein. When rats were fed 6% casein for 13 d and then fed the same 6% casein diet with or without an additional 15% ammonium acetate for an additional 7 d before feeding 75% casein for 1 d, the plasma ammonia concentration of each group was not different, but plasma and brain amino acid concentrations were lower in rats prefed 15% ammonium acetate before the 75% casein diet. When rats were fed 6.8% egg white for 9 d and then fed 27.9% egg white for an additional 7 d, food intake of rats fed the 27.9% egg white diet was lower (P less than 0.05, paired t-test) for 4 d compared with that during the 3-d pretest period. When rats were meal-fed the 6.8% egg white diet for 13 d and then fed either the same 6.8% egg white diet or the 27.9% egg white diet for 1 d, plasma ammonia and plasma and brain amino acid concentrations were higher at 5 h after test meal initiation (P less than 0.05) in rats fed 27.9% egg white compared to those of rats fed 6.8% egg white. At 23 h after test meal initiation, plasma ammonia, plasma amino acid and most brain amino acid concentrations were lower than they were at 5 h after test meal initiation in rats fed 27.9% egg white.

Amino Acids↗
PubMed1998

Mitochondrial lysine uptake limits hepatic lysine oxidation in rats fed diets containing 5, 20 or 60% casein.

Sixty male Sprague-Dawley rats were randomly allotted to receive diets containing 5, 20 or 60% casein. Rats had access to the diet only during the initial 8 h of the daily 12-h dark period. Hepatic mitochondrial lysine uptake, lysine alpha-ketoglutarate reductase (LKR) and saccharopine dehydrogenase (SacD) activities, and in vitro lysine oxidation (LOX) were measured 0, 6, 12, 18 and 24 h after the start of the dark period. Diurnal variation of mitochondrial lysine uptake was not detected (P > 0.10) although uptake varied 3-fold over 24 h. Mitochondrial lysine uptake was greater (P < 0.05) for rats fed diets containing 60% casein than for rats fed diets containing 5% casein. Diurnal variation of LKR was detected (P < 0. 05) in rats fed diets containing 20 and 60% casein. Diurnal variation of SacD was detected (P < 0.05) in rats fed diets containing 60% casein. Increased casein consumption resulted in increased LKR and SacD activities (4- to 5-fold; P < 0.05). Diurnal variation of LOX was detected in rats fed diets containing 20 and 60% casein (P < 0.05). Increasing the casein concentration in the diet from 5 to 60% resulted in a 7-fold increase in LOX (P < 0.05). To make rate comparisons, LKR and SacD activities and LOX were predicted from a range of substrate concentrations (0.1 to 5.0 mmol/L). Overall, LKR and SacD were 6-107 times that of LOX, suggesting that, in liver, mitochondrial lysine uptake limits LOX.

Administration, Oral↗
PubMed2001

Opioid and cholecystokinin antagonists alleviate gastric inhibition of food intake by premeal loads of casein in meal-fed rats.

This study was undertaken to determine whether casein, compared with its constituent amino acids, given at the onset of a meal, would influence intake due to cholecystokinin (CCK) or opioid activity. Male Sprague-Dawley rats (n = 80; 225 g) were given either premeal loads of casein or its constituent amino acids and treated with opioid or CCK antagonists in a 2 x 4 factorially designed experiment. During a 21-d period, rats were meal-fed by restricting access to food to 5 h/d. The rats were fed the AIN-93 diet with soy isolate substituted for casein as the dietary protein source. On d 7-21, rats were given oral premeal loads of 5 mL of a 50 g/L casein or constituent amino acid solution before meal-feeding. On d 14-21, 20 rats were injected intraperitoneally with one of the following treatments: saline, naltrexone (l mg/kg), naloxone methiodide (5 mg/kg) or lorglumide (1 mg/kg) before the premeal load and feeding. Antagonist treatments increased intake (P < 0.05) by 15.3% compared with saline treatment (7.82 vs. 9.02 g/d) in rats given premeal loads of casein. Intake of rats given premeal loads of amino acids was not influenced by antagonists. At 2 h after feeding on d 21, the rats were killed, bled and eviscerated. Effects of antagonists on stomach and intestinal mass, digesta contents and fecal output were also dependent on the type of premeal load, indicating that gastric retention of digesta due to casein was mediated by CCK and opioids. Body weight accretion, liver, and epididymal fat mass and blood concentrations of specific amino acids changed in the same manner as intake (P < 0.05). Serum insulin was greater (P < 0.05) in casein-treated rats and reduced (P < 0.01) by opioid antagonists. Satiety associated with premeal loads of casein is related to changes in gastrointestinal function of meal-fed animals and involves both opioid and CCK regulation.

Amino Acids↗
PubMed1999

Cytosol is required for the modulation by dietary casein of the hepatic microsomal activation of aflatoxin B1 to mutagenic metabolites detectable in Salmonella.

We have shown previously that dietary protein (casein) levels can affect the ability of rat liver S9 to metabolize aflatoxin B1 (AFB) as well as other promutagens detectable in Salmonella strain TA98 [Mutat. Res. (1997), 360, 115-126 and 127-143]. The mutagenic potency of AFB was greatest when metabolized by the Aroclor 1254-induced hepatic S9 prepared from F344 male rats that consumed an isocaloric, semisynthetic diet for 6 weeks that contained an adequate (12%) level of methionine-supplemented casein as the sole protein source, compared with S9s from rats fed diets that contained nominally deficient (8%) or high (22%) levels of casein. Here we have extended this observation by performing (i) mutagenicity studies with microsomes, cytosols and reconstituted S9s (recombinations of microsomes and cytosols across dietary groups), and (ii) in vitro incubations followed by analysis of metabolites by fluorescence high-pressure liquid chromatography. Microsomes, but not cytosols, activated AFB; however, activation to the level observed with S9 occurred only when microsomes from the rats fed 12% casein were combined with cytosols from any dietary group. Consistent with the mutagenicity results, the greatest metabolism of the AFB parent compound and the highest level of the glutathione conjugate of the presumptively identified AFB-exo-8,9-epoxide (the ultimate mutagenic form of AFB) were produced by S9s from the rats fed the 12% casein diet. The levels of these metabolites and the mutagenicity of AFB changed in parallel with changes in dietary casein levels. In summary, cytosolic elements, which are not affected by dietary casein levels, interact with microsomal enzymes, which are modulated by dietary casein levels, to influence the ability of hepatic S9 to activate AFB to a mutagen.

Aflatoxin B1↗
PubMed1982

Rat beta casein cDNA: sequence analysis and evolutionary comparisons.

The complete sequence of a 1072 nucleotide rat beta-casein cDNA insertion in the hybrid plasmid pC beta 23 has been determined. Primer extension was employed to determine the sequence of an additional 82 5'-terminal nucleotides in beta-casein mRNA. Rat beta-casein mRNA consists of a 696 nucleotide coding region, flanked by 52 nucleotide 5' and 406 nucleotide 3' noncoding regions, including a 40 nucleotide poly(A) tail. The derived 216 amino acid sequence of rat beta-casein was compared to the previously determined sequences of beta-caseins from several other species. Approximately 38% of the amino acids have been conserved among the rat, ovine, bovine and human sequences and these conserved amino acids occurred in clusters throughout the protein. One such cluster containing the majority of the potential casein phosphorylation sites was located near the amino terminus. Contrary to the considerable divergence observed for the processed beta-casein, 14 of 15 amino acids in the signal peptide sequence of the precasein were identical between the rat and ovine caseins.

Amino Acid Sequence↗
PubMed1988

Tissue-specific expression of the rat beta-casein gene in transgenic mice.

The rat beta-casein gene is a member of a small gene family, encoding the principal milk proteins. In order to understand the mechanisms by which its stage- and tissue-specific expression are regulated, initially, a 14 kb genomic clone containing the entire 7.5 kb rat beta-casein gene with 3.5 kb of 5' and 3.0 kb of 3' flanking DNA was microinjected into the germline of mice. Eight F0 transgenic mice were generated with copy numbers ranging from 1-10; five transmitted the transgene to their offspring in a Mendelian pattern. A specific RNase protection assay was developed to quantitate the level of expression of the rat beta-casein transgene as compared to the endogenous mouse beta-casein gene. Using this assay expression was demonstrated predominantly in the lactating mammary gland of transgenic mice at a level of 0.01-1% of the endogenous mouse beta-casein gene. The transgene employed the authentic transcription initiation site observed previously in the analogous rat beta-casein gene. In one line, a reduced level of expression of the transgene was also observed in the brain. The site of integration, therefore, plays an important role in influencing the level of expression of the transgene, but not its general pattern of tissue-specificity. The transgene appears to be developmentally-regulated in accordance with the endogenous mouse beta-casein gene. These lines of mice generated carrying the rat beta-casein transgene should provide useful models for studying the developmental and hormonal regulation of milk protein gene expression.

Animals↗
PubMed1980

Alpha-casein-binding proteins of guinea pig macrophage membranes and their possible roles in chemotaxis.

The existence of specific binding proteins for alpha-casein, a well-known potent chemoattractant, on guinea pig peritoneal macrophages was demonstrated. Binding of 3H-alpha-casein to macrophages was found to be specific and reversible. Its association constant and the number of binding sites were 5.0 X 10(-6) M and 7.5 X 10(5) per cell, respectively. The presence of formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe), another chemoattractant, at a chemotactically active concentration (10(-11) to 10(-6) M) reduced this binding significantly. Pretreatment of macrophages with proteases such as trypsin and chymotrypsin decreased the number of binding sites for alpha-casein and the chemotactic response to alpha-casein. alpha-Casein binding proteins were isolated from radiolabeled macrophage surface membranes by affinity chromatography on a column of alpha-casein Sepharose 4B. SDS-polyacrylamide gel electrophoresis of the isolated proteins revealed three radioactive bands; two (MW 130,000 and 65,000) were glycoproteins, and the other (MW 100,000) was a protein which contained little carbohydrate. These three proteins were also isolated from the same source by affinity chromatography using a column of fMet-Leu-Phe-AH-Sepharose. This result, together with the observation that fMet-Leu-Phe inhibited the binding of alpha-casein to macrophages, indicated that alpha-casein and the tripeptide have at least partly common binding sites on guinea pig macrophages. Some of the proteins obtained in this work may constitute chemotactic receptors on the macrophage membrane.

Animals↗
PubMed1993

Overproduction of bovine beta-casein in Escherichia coli and engineering of its main chymosin cleavage site.

A cDNA clone containing the entire coding region for bovine beta-casein A3 flanked by 53 base pairs of 5' non-coding and 358 base pairs of 3' non-coding sequences was isolated from a bovine mammary cDNA phagemid library. The coding segment for mature beta-casein was subcloned into the T7 expression system, in which the expression of recombinant beta-casein was controlled by the T7 gene 10 promoter and ribosome binding site. High level expression of Met-beta-casein to approximately 20% of the total soluble proteins was obtained in Escherichia coli within 2 h after induction of T7 RNA-polymerase synthesis. In an attempt to induce secretion the coding segment for mature beta-casein was coupled to the ompA translational initiation signal and signal peptide coding sequence but no secretion of the fusion protein and no processing of the signal peptide from the fusion protein was observed. Instead, the Met-beta-casein could be isolated in a soluble form from E.coli cells after an osmotic shock, indicative of a periplasmic location. This procedure did not lyse the cells. The protein was purified to homogeneity after a pH 4.8 isoelectric precipitation followed by reversed-phase high-performance liquid chromatography. The beta-casein cDNA was altered to change the main chymosin cleavage site in beta-casein at position 192-193 in two ways, namely from Leu-Tyr to Pro-Pro and to Leu-stop.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Human milk kappa-casein and inhibition of Helicobacter pylori adhesion to human gastric mucosa.

Readily digested caseins, which account for almost half of the protein content in human milk, are important as nutritional protein for breast-fed infants. It has also been advocated that part of the antimicrobial activity of human milk resides in the caseins, most likely the glycosyated K-casein. Top explore this possibility, we purified K-casein from human milk to homogeneity by a two-step size-exclusion chromatography procedure. Purified human K-casein, in contrast to K-casein purified from bovine milk, effectively inhibited the cell lineage-specific adhesion of fluoroisothiocyanate-labeled Helicobacter pylori to human gastric surface mucous cells. The inhibitory activity was abolished by metaperiodate oxidation and considerably reduced by preincubation with alpha-L-fucosidase but not with alpha-N-acetylneuraminidase or endo-beta-galactosidase. These results strongly support the view that fucose containing carbohydrate moieties of human K-casein are important for inhibition of H. pylori adhesion and, thus, infection. They also suggest that breastfeeding may protect from infection by H. pylori during early life and that species-specific glycosylation patterns, as illustrated by human bovine K-casein, partly determine both the narrow host spectrum of this human gastric pathogen and the capacity to resist infection.

Animals↗
PubMed1995

Casein haplotypes and their association with milk production traits in the Finnish Ayrshire cattle.

Polymorphism of casein genes was studied in half-sib families of artificial insemination bulls of the Finnish Ayrshire dairy breed. Ten grandsires and 300 of their sons were genotyped for the following polymorphisms: alpha s1-casein (B, C), beta-casein (A1, A2), the microsatellite within the kappa-casein gene (ms5, ms4) and kappa-casein (A, B, E). Nine different combinations of these alleles, casein haplotypes, were found. Associations between casein haplotypes and milk production traits (milk and protein yield, fat and protein percentage and milking speed) were studied with ordinary least-squares analysis to find a direct effect of the haplotypes or an association within individual grandsire families using the granddaughter design. Estimated breeding values of sons were obtained from cow evaluation by animal model. No direct effect of the casein haplotypes on the traits was found. Within grandsire families, in one out of four families the chromosomal segment characterized by haplotype 3 (B-A2-ms4-A) was associated with an increase in milk yield (P < 0.01) and a decrease in fat percentage (P < 0.01) when contrasted with haplotype 8 (B-A1-ms4-E). The results provide evidence that in the Finnish Ayrshire breed at least one quantitative trait locus affecting the genetic variation in yields traits is segregating linked to either haplotype 3 (B-A2-ms4-A) or 8 (B-A1-ms4-E).

Animals↗
PubMed1982

Nucleotide sequence of cloned cDNA coding for mouse epsilon casein.

We isolated cDNA clones, which correspond to the mRNA coding for the smallest of the seven mouse caseins. From the nucleotide sequence of the cDNA we deduced the amino acid sequence of the protein, which we named epsilon casein. Mouse epsilon casein and cow alpha s2 casein show amino acid sequence homologies in the N-terminal region of the mature protein. The signal peptide of mouse epsilon casein shows in length and sequence remarkable homology to the signal peptides of the calcium-precipitable caseins of other species. In accordance with this group of caseins mouse epsilon casein contains in the sequence -Ser-Ser-Glu-Glu- a site for potential multiple phosphorylation.

Animals↗
PubMed2002

Immunochemical demonstration of alpha(s1)- and beta-casein in mouse mammary glands at early stages of pregnancy.

We generated monoclonal antibodies (MAbs) against mouse alpha(s1)- and beta-casein and used them to survey casein immunochemically in mammary glands of mice at peri-coitous and pregnant stages. Two MAb-producing hybridoma cells, designated MCalpha1 cell and MCbeta1 cell, were established. Each antibody, when used in Western blotting, recognized specifically mouse alpha(s1)- and beta-casein among a wide spectrum of proteins of both a lactating mammary homogenate and mouse skim milk. Immunohistochemistry revealed alpha(s1)- and beta-casein in sections of lactating mammary glands. Staining was found in substances in the lumen and cytoplasm of duct and alveolar cells, particularly in rough endoplasmic reticulum and the Golgi apparatus. Mammary glands at Days 2, 4, 6, 8, and 14 of pregnancy showed positive staining specific to both alpha(s1)- and beta-casein in the lumen and cytoplasm of duct cells, whereas the glands at estrus and Day 0 of pregnancy were positive mainly for alpha(s1)-casein. Semiquantitative Western blotting analysis of both casein components in epithelial cell fractions from glands during pregnancy confirmed that intra-epithelial alpha(s1)- and beta-casein changed during three phases, elevated from trace levels to detectable levels during initial stages of pregnancy (Days 0, 2, and 4), declined to lower levels during mid-pregnancy (Days 6 and 8), and then rose to high levels during late pregnancy (Day 14).

Animals↗
PubMed2003

Casein binds to the cell membrane and induces intracellular calcium signals in the enteroendocrine cell: a brief communication.

Dietary protein but not amino acids stimulates cholecystokinin (CCK) secretion in rat mucosal cells. However, the dietary protein sensory mechanisms and the intracellular signal pathway in the enteroendocrine cells have not yet been clarified. The relationship between dietary protein binding to cell membrane and intracellular calcium responses were examined in the CCK-producing enteroendocrine cell line STC-1. The binding of solubilized STC-1 cell membrane to proteins was analyzed using a surface plasmon resonance sensor. Intracellular calcium concentrations of STC-1 cell suspensions loaded with Fura-2 AM were measured using a spectrafluorophotometer system with continuous stirring. Intracellular calcium concentrations in STC-1 cells were increased by exposure to alpha-casein or casein sodium, but not to bovine serum albumin. Solubilized STC-1 membranes bound to alpha-casein and casein sodium but did not bind to bovine serum albumin. alpha-Casein demonstrated higher membrane binding and intracellular calcium stimulating activities than casein sodium. Thus, protein binding to the STC-1 cell membrane and intracellular calcium responses were correlated. Intracellular calcium responses to alpha-casein were suppressed by an L-type calcium channel blocker. These results suggest that casein, a dietary protein, binds to a putative receptor on the CCK-producing enteroendocrine cell membrane and elicits the subsequent intracellular calcium response via an L-type calcium channel.

Animals↗
PubMed1989

Hormone-dependent beta-casein mRNA stabilization requires ongoing protein synthesis.

The role of ongoing protein synthesis in mediating the posttranscriptional effects of hormones on casein gene expression in the COMMA D mouse mammary epithelial cell line was investigated using the protein synthesis inhibitors, cycloheximide and anisomycin. When COMMA D cells were pretreated with insulin and PRL for 24 h, the addition of glucocorticoids induced a greater than 20-fold increase in beta-casein mRNA accumulation with an apparent lag of greater than 8 h. Addition of cycloheximide and anisomycin not only prevented this increase, but unexpectedly, resulted in the rapid disappearance of preexisting beta-casein mRNA with a half-life of approximately 2 h. Under the same conditions, the levels of beta-actin and histone H4 mRNAs were increased markedly. In contrast, when cells were pretreated with all three lactogenic hormones for 48 h before the addition of either protein synthesis inhibitors or actinomycin D, the effects of these inhibitors on the levels of beta-casein mRNA were greatly diminished. This differential sensitivity of beta-casein mRNA to protein synthesis inhibitors was observed only in cells pretreated for greater than 24 h with all three hormones. Experiments performed in the absence of inhibitors indicated that beta-casein mRNA has a long half-life even after hormone withdrawal. These results suggest that hormone-dependent stabilization of cytoplasmic beta-casein mRNA requires ongoing protein synthesis. Cells cultured in the presence of all three lactogenic hormones slowly accumulate a labile protein(s), which exerts a selective effect on casein mRNA stability.

Actins↗
PubMed1997

A casein kinase I isoform is required for proper cell cycle progression in the fertilized mouse oocyte.

Casein kinase I is a family of serine/threonine protein kinases common to all eukaryotes. In yeast, casein kinase I homologues have been linked to the regulation of growth, DNA repair and cell division. In addition, their subcellular localization to membraneous structures and the nucleus is essential for function. In higher eukaryotes, there exist seven genetically distinct isoforms: (alpha), ss, (gamma)1, (gamma)2, (gamma)3, (delta) and (epsilon). Casein kinase I(alpha) exhibits a cell cycle-dependent subcellular localization including an association with cytosolic vesicular structures and the nucleus during interphase, and the spindle during mitosis. casein kinase I has also been shown to modulate critical regulators of growth and DNA synthesis/repair in mammalian cells such as SV40 large T antigen and p53. These results suggest that casein kinase I may be involved in processes similar to those ascribed to the yeast casein kinase I homologues. To define a role for casein kinase I(alpha) in cell cycle regulation, the mouse oocyte was utilized because of its well-defined cell cycle and ease of micromanipulation. Immunofluorescence studies from meiosis I of maturation to the first zygotic cleavage demonstrated that the kinase was associated with structures similar to those previously reported. Microinjection of casein kinase I(alpha) antibodies at metaphase II-arrest and G2 phase, had no effect on the completion of second meiosis or first division. However, microinjection of these antibodies during the early pronucleate phase prior to S-phase onset blocked uptake of the kinase into pronuclei and interfered with proper and timely cell cycle progression to first cleavage. These results suggest that the kinase regulates the progression from interphase to mitosis during the first cell cycle.

Animals↗