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P J Buttery

Publications and source records attributed to P J Buttery.

At least 37 records · Page 2Linked to original sources
PubMed1999

Relationship between skeletal muscle-specific calpain and tenderness of conditioned porcine longissimus muscle.

Tenderization of skeletal muscle in meat animals has been closely linked to the postmortem activity of the calpain proteolytic enzyme system, which includes the specific inhibitor calpastatin. Increased understanding of the skeletal muscle-specific calpain isoform p94 has prompted suggestions as to whether it too could have a role in the tenderization process. In this study, two groups of pigs were identified in which shear force measurements after 8 d of conditioning indicated a large variation in the tenderness of longissimus muscle. The quantity of p94 in the muscle was monitored by immunoblotting, using a porcine-specific polyclonal antibody raised against a recombinant peptide fragment generated as a fusion protein. The antiserum recognized a 94-kDa protein associated with myofibrils in skeletal but not cardiac muscle, as expected for this calpain isoform, although it could not be tested with the native protein because of the extreme instability of p94. In the first experiment, the mean shear force for the tough group was 6.71 +/- .28 kg (n = 12, SEM) and that of the tender group was 3.87 +/- .12 kg (n = 12), but there was no difference in the normalized absorbance of the immunopositive 94 kDa band on Western blots from samples collected at approximately 40 min postmortem. In the second experiment, the stability of p94 in chilled carcasses was investigated over 24 h, using a further two groups of 10 tough and 10 tender pigs of mean shear force values 5.36 +/- .14 kg and 2.81 +/- .15 kg, respectively. In tough and tender animals, there was a decline (P < .05) in the 94-kDa immunostaining material of mean half-lives of 13.8 and 12.9 h, respectively, although there was considerable variability. Despite this variability in half lives and shear force values, no correlation was seen between these factors. Thus, in porcine longissimus muscle, the variability in tenderness after 8 d of conditioning cannot be attributed to an underlying variability in p94.

Animals↗
PubMed1999

Ubiquitin gene expression and ubiquitin conjugation in chicken muscle do not reflect differences in growth rate between broiler and layer birds.

Previous work has shown that chicken strains selected for growth (broilers) degrade muscle proteins less rapidly than those selected for egg laying. They also have decreased calpain and increased calpastatin content in breast muscle. This study aimed to test the hypothesis that these differences correlate with changes in the ATP- and ubiquitin-dependent proteolytic system. Chickens of a broiler strain (Ross 1) and a layer strain (ISABrown) were reared to the age of 4 wk under identical conditions with ad libitum access to feed and water. Mean fractional growth rates were 10.4%/d for broilers and 7.4%/d for layers. Feed intake measured in the last week of the trial was slightly greater in layer birds (.11 and .12 g x g body weight(-1) x d(-1) for broilers and layers respectively; P < .006). Polyubiquitin (UbI) messenger RNA was abundant in the muscles of these well-fed birds, but it showed little difference between strains. Muscle did not significantly express the UbII polyubiquitin gene. The ATP-dependent system conjugating ubiquitin to endogenous proteins had greatest activity in the gastrocnemius muscle of broiler birds but was not significantly different between breeds. Proteins cross-reactive with antisera to recombinant human proteasome regulatory subunits MSS1 (multicopy suppressor of SUG 1; S7) and TBP1 (tat binding protein 1; S6') were present in muscle homogenates from both strains of bird. The chick equivalent of TBP1 was more abundant in breast muscle of broiler birds than in leg muscle, or in either muscle of layers. Antiserum to recombinant yeast subunit mts2 (mitosis temperature sensitive gene 2; S4) did not react with any protein of the expected size but detected a 30-kDa peptide that was not associated with the 26S proteasome; this was found only in muscle from the layer strain. Hence, during normal growth of chickens, rates of protein degradation are not controlled by the expression of ubiquitin mRNA or the conjugation of ubiquitin. However, the composition of the 26S proteasome may be a regulatory factor.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1998

Stearoyl-CoA desaturase mRNA is transcribed from a single gene in the ovine genome.

Clones corresponding to ovine stearoyl-CoA desaturase (SCD) cDNA were isolated from an adipose tissue cDNA library. All of these clones represented a single mRNA species as judged by restriction fragment and DNA sequence analysis. RNase protection analysis demonstrated that this SCD transcript is highly expressed in adipose tissue and liver, and in the mammary gland of lactating animals. A lower level of expression was detectable in a variety of other tissues including brain. Levels of the SCD transcript were decreased in adipose tissue during lactation, and this appears to be related to a marked decline in serum insulin and insulin-responsiveness of the tissue. Southern analysis of ovine and mouse genomic DNA demonstrated that the ovine SCD cDNA hybridised in a manner consistent with a single gene for SCD in ovine DNA; mouse genomic DNA produced a pattern of hybridisation consistent with the previously characterised mouse SCD-1 and SCD-2 genes. Three ovine cosmids were isolated that comprised the restriction fragments predicted by the genomic Southern analysis. The ovine SCD gene was predicted to be encompassed within a 23 kbp region that was present in all three cosmids. These results demonstrate that SCD is transcribed from a single gene in the ovine genome and this gene is insulin-responsive in ovine adipose tissue.

Adipose Tissue↗
PubMed1998

The interaction between nutritional status and growth hormone in young cattle: differential responsiveness of fat and protein metabolism.

The effect of dietary intake level on in vivo plasma leucine and plasma palmitate flux rates and on the response to a bolus injection of bovine growth hormone (GH) was investigated in six young steers. Animals were fed on a pelleted diet of dried grass-barley (0.7:0.3, w/w) in quantities sufficient to supply 0.8, 1.2, 1.6, 2.0, 2.4 or 2.65 x maintenance energy requirement, offered in hourly portions. Continuous intravenous infusions of [1-13C]leucine or [1-13C]palmitate were used to determine the flux of amino acid and fatty acid through the plasma pool before, immediately (1-3 h) after and 22-24 h after a subcutaneous injection of bovine GH (0.55 mg/kg body weight). Hourly blood samples were taken for 27 h to monitor the temporal responses of circulating hormones and metabolites following GH administration. The animal on the lowest plane of nutrition had elevated plasma GH and reduced insulin-like growth factor-1 concentrations compared with those fed on higher intake levels. Plasma leucine flux and leucine concentration increased with intake while palmitate flux and plasma non-esterified fatty acid (NEFA) concentrations were inversely related to intake. Leucine flux rate decreased in the animals fed on the two highest intake levels in response to GH 22-24 h after administration, but plasma leucine concentrations were reduced in all animals at this time. Only the animal fed on the lowest intake level showed an immediate response to GH (within 3 h of administration) with increased palmitate flux and plasma NEFA concentrations but a lipolytic response was apparent in other animals 22-24 h post-administration although the magnitude of the response was markedly reduced at high intakes. We conclude that lipid and protein metabolism are differentially responsive to GH and nutritional status.

Animals↗
PubMed1996

Effect of lactation on insulin signal transduction in sheep adipose tissue and skeletal muscle.

The molecular basis of the insulin resistance of adipocytes and skeletal muscle during lactation has been investigated in sheep. The number of insulin receptors per adipocyte or per unit membrane protein for skeletal muscle is unchanged by lactation. The ability of insulin to stimulate autophosphorylation of its beta-subunit was enhanced in adipocytes but not in skeletal muscle during lactation. This increased autophosphorylation was due, at least in part, to enhanced tyrosine phosphorylation and was found when both solubilised, immunoprecipitated insulin receptors and intact adipocytes were incubated with insulin. The ability of the insulin receptor kinase to phosphorylate other proteins did not appear to be altered by lactation; this was shown with lectin-purified insulin receptors using the artificial substrate, polyglutamyl tyrosine, and in intact adipocytes. Lactation had no effect on the ability of insulin to activate two key downstream kinases, mitogen-activated protein kinase and phosphatidyl inositol-3-kinase in adipocytes. The study thus shows that the insulin resistance of lactation in sheep is due to changes downstream of the receptor in both adipocytes and skeletal muscle.

Adipose Tissue↗
PubMed1996

The relationship between plasma epinephrine concentration and the activity of the calpain enzyme system in porcine longissimus muscle.

The relationship between plasma epinephrine and postmortem activity of the calpain system in porcine longissimus muscle was investigated. Two groups of Large White pigs were continuously infused intravenously with either placebo (control) or epinephrine (treated) at a rate of .15 micrograms.kg-1.min-1 for a period of 1 wk before slaughter. Samples of longissimus muscle were taken at 0, 1, 2, 4, 8, 24, 48, and 192 h (t0 to t192) after slaughter and immediately snap-frozen in liquid nitrogen for subsequent analysis of mu-calpain, m-calpain, and calpastatin activity. Epinephrine infusion had no effect on the activities of mu- and m-calpain at t0. Calpastatin activity at t0 was increased (P < .01) in treated pigs by 97%. The ratio of total calpain:calpastatin activity at t0 was reduced (P < .01) in treated pigs. The activity of mu-calpain decreased rapidly after slaughter, irrespective of treatment, dropping to less than 10% of the initial activity within 8 h. The activity of m-calpain also decreased over the first 8 h, although the rate of decrease was less (P < .05) in treated pigs. Consequently, m-calpain activity remained greater in treated pigs compared with controls throughout the period normally associated with tenderization. Postmortem values for calpastatin activity tended to be highly variable, with activities being similar between control and treated pigs within 1 h after slaughter. Over the entire 192 h sampling period, calpastatin activity decreased (P < .001), although the effect was independent of treatment. In general the results imply that variations in plasma epinephrine concentrations, which may naturally occur as part of the stress response, perturb the calpain enzyme system.

Animals↗
PubMed1996

Effects of growth hormone administration and dietary protein intake on insulin-like growth factor I and growth hormone receptor mRNA Expression in porcine liver, skeletal muscle, and adipose tissue.

The effects of growth hormone (GH) and dietary protein on expression of IGF-I and GH receptor (GHR) genes in liver, muscle, and fat of pigs were investigated. Forty-eight intact male Large White x Landrace pigs were allotted to eight treatment groups (four diets with or without GH). The pigs were restriction-fed one of four diets, which differed only in their protein content (9.9, 13.1, 16.2, and 19.4%, as-fed basis), for a total of 3 wk. The pigs were then injected intramuscularly with either porcine GH (50 micrograms.kg-1.d-1 of rpST) or vehicle for the last 7 d. Pigs were slaughtered 4 h after the final injection. Total RNA was extracted from all tissues and then RNase protection assays were performed to measure expression of IGF-I and GHR genes. Expression of IGF-I mRNA was found to be GH responsive in the liver, semitendinosus (ST), and adipose tissue (P < .01) but not in longissimus muscle (LD). Dietary protein increased IGF-I expression only in the adipose tissue (P < .01). Expression of class 2 transcripts of IGF-I were observed only in the livers of GH-treated pigs, with no effect of dietary protein. Expression of GHR mRNA was found to increase with GH administration in liver and skeletal muscle (LD and ST, P < .05) but not in adipose tissue. There were diet x GH interactions on GHR expression in liver, ST, and adipose tissue, resulting in the highest GHR expression being in the high protein-fed, GH-treated group for liver, but in the low protein-fed, GH-treated group for muscle and adipose tissue. This study demonstrates tissue-specific control of expression of the two genes and also tissue-specific promoter usage (IGF-I exon 2 in liver) in response to GH administration.

Adipose Tissue↗
PubMed1995

Effects of growth factors and gut regulatory peptides on nutrient uptake in ovine muscle cell cultures.

Effects of gut regulatory peptides and growth factors on the uptake of 2-aminoisobutyric acid (AIB) and 2-deoxy-D-glucose (2-DOG) were examined in differentiated ovine satellite cell cultures. Insulin and insulin-like growth factor I (IGF-I) gave maximal increases of 160-180% of controls for AIB and over 190% for 2-DOG. IGF-I showed half-maximal effects at 0.1-1 nM, and insulin at 1-10 nM. Bovine growth hormone (0.01-100 nM) had no effect. Gastrin, gastric inhibitory polypeptide (GIP), bombesin and somatostatin had no action in either the absence or presence of insulin. In primary cultures epidermal growth factor (EGF) increased the uptake of AIB (133-137%) and 2-DOG (171-176%). In clonal lines, EGF had little effect on nutrient uptake but still simulated protein synthesis.

Aminoisobutyric Acids↗
PubMed1995

Glucocorticoids and insulin but not growth hormone modulate insulin binding to adipocyte membranes from sheep.

Mechanisms by which the glucocorticoid analogue dexamethasone and growth hormone modulate insulin action in sheep adipose tissue have been investigated. Maintenance of sheep adipose tissue in culture for 48 hr in the absence of exogenous hormones resulted in a decrease in insulin binding to adipocyte membranes; this was prevented by the inclusion of 10 nM dexamethasone during culture. Tissue culture for 48 hr with insulin itself decreased insulin binding to adipocyte membranes, whereas tissue culture with growth hormone had no effect on insulin binding. Neither dexamethasone nor growth hormone altered the ability of insulin to decrease insulin binding to its receptor. The study shows that the insulin-antagonistic effects of growth hormone on sheep adipose tissue metabolism are due to an effect subsequent to insulin binding to its receptor, whereas some of the effects of dexamethasone may be due to an increase in the insulin-binding capacity of membranes.

Adipocytes↗
PubMed1995

The effects of fasting on the thermogenic, metabolic and cardiovascular responses to infused adrenaline.

The effects of fasting on the thermogenic, lipolytic and cardiovascular responses to adrenaline were examined in nine normal, young, non-obese subjects. Each subject attended for study after 12, 36 and 72 h fasting. After basal measurements adrenaline was infused at 25 ng/min per kg ideal body weight for 90 min. Fasting increased the thermogenic effect of the adrenaline (mean 14.6 (SE 1.7), 16.6 (SE 1.8), 22.6 (SE 1.6) J/min per kg fat-free mass after 12, 36 and 72 h fasting respectively; P < 0.001, ANOVA). Basal plasma palmitate turnover increased with duration of fasting (1.48 (SE 0.22), 1.95 (SE 0.34) and 2.26 (SE 0.33) mumol/min per kg body weight; P < 0.001, ANOVA), but the response to adrenaline was unaffected by fasting. The percentage values for basal plasma palmitate turnover oxidized were 44 (SE 2; 12 h), 46 (SE 5; 36 h) and 42 (SE 4)% (72 h). In response to adrenaline this percentage fell, suggesting that adrenaline infusion may favour intra-tissue lipid oxidation.

Adult↗
PubMed1995

Hormonal control of insulin-like growth factor-I and growth hormone receptor mRNA expression by porcine hepatocytes in culture.

The effects of various hormones commonly added to hepatocyte culture media upon the expression of the GH receptor (GHR) and insulin-like growth factor-I (IGF-I) genes in cultured porcine hepatocytes were investigated. Preliminary investigations indicated that there was an absolute requirement only for insulin, with high losses of cell viability upon long term exclusion of insulin from the culture medium. The decline in GHR expression with time in culture was found to be less when high levels of glucose were included in the medium. Therefore the basal culture medium used in these studies was Williams' medium E supplemented with 0.2% (w/v) BSA, 5000 mg glucose/l and 100 nmol porcine insulin/l. The addition of dexamethasone (10 nmol/l) increased the expression of both GHR and IGF-I (class 1 transcripts only) mRNA (p < 0.001 and P < 0.05 respectively), and resulted in an increased responsiveness of IGF-I mRNA expression to GH (1 microgram/ml), when the two were added in combination (although only class 1 transcripts were shown to be statistically significant, P < 0.01). The addition of either thyroid hormone (1 nmol/l T3 or T4) alone also increased the expression of GHR mRNA (P < 0.01) in addition to the dexamethasone stimulated expression, with T4 appearing to decrease IGF-I expression slightly (P < 0.05) (either on its own or with T3). As with dexamethasone, the thyroid hormones increased the response of IGF-I mRNA expression to GH (1 microgram/ml) when added in combination with GH (P < 0.001). These observations demonstrate one possible mechanism for the interactions of glucocorticoids and thyroid hormones with the GH-IGF axis.

Animals↗
PubMed1994

Effect of insulin and isoproterenol on lipid metabolism in porcine adipose tissue from different depots.

Significant differences were found in the rates of lipogenesis, glucose oxidation and lipolysis in porcine adipose tissue from four depots; outer subcutaneous (OSC), middle subcutaneous (MSC), perirenal (PR) and omental (OM). Lipogenesis was stimulated by insulin in all depots in the order PR > OM > MSC > OSC. Lipolysis was stimulated by isoproterenol in all depots in the order PR > OM > MSC > OSC. Differences in lipid metabolism by the different depots may have an important impact on lipid accretion in vivo.

Adipocytes↗