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T Parr

Publications and source records attributed to T Parr.

At least 19 recordsLinked to original sources
PubMed2006

Effect of anabolic agents on calpastatin promoters in porcine skeletal muscle and their responsiveness to cyclic adenosine monophosphate- and calcium-related stimuli.

The calpain proteinases and their specific inhibitor calpastatin have been proposed to influence both the rates of myofibrillar protein turnover in vivo and meat tenderization postmortem. Elevated calpastatin concentrations in particular are associated with certain forms of hypertrophic growth and meat toughness. In the 5'region of the porcine calpastatin gene, there are 3 calpastatin promoters upstream of exons 1xa, 1xb, and 1u, respectively, each of which contain transcription factor-binding motifs, suggesting sensitivity to a variety of growth-promoting stimuli. This study examined the effect of the beta-adrenergic agonist clenbuterol and porcine ST (pST) treatment on calpastatin promoter usage in porcine LM in vivo using real-time PCR and also the responsiveness of transfected calpastatin promoter sequences to cyclic adenosine monophosphate (cAMP) and calcium (Ca2+)-related stimuli in reporter gene systems in cell studies. The effect of clenbuterol and pST on potential signaling pathways in vivo was also assessed by monitoring protein phosphatase 2B (calcineurin), NFATc3, calpain 3, IkappaB alpha, and NFkappaB by quantitative immunoblotting. Total calpastatin mRNA was increased by 52% (P < 0.05) after treatment with clenbuterol for 1 d and reduced by 35% (P < 0.01) after pST treatment for 7 d. Whereas clenbuterol had no significant differential effects on individual mRNA transcripts (types 1 to 3) derived from the 3 upstream promoters, pST significantly reduced all of these by 51, 39, and 40% (P < 0.001, 0.05, and 0.05), respectively. Promoter activity was increased in rat L6G8 cells transfected with a construct derived from exon 1u after treatment with dibutyryl cAMP (68%, P < 0.05) or forskolin (43%, P < 0.05), whereas 1xa activity was reduced by both of these agents (47 and 33%, respectively, P < 0.05). Treatment of cells with the calcium ionophore calcimycin reduced the activity of the 1u promoter by 40% (P < 0.01), with no effect on the other promoter constructs. Cyclosporin A had no effect on any promoter construct. The only signaling pathway component to be significantly altered by the in vivo treatments was calcineurin, which was decreased by 24% (P < 0.05) in clenbuterol-treated animals. In conclusion, 2 types of growth promoter in pigs had contrasting effects on calpastatin expression in LM. Transfected calpastatin promoters were differentially sensitive to cAMP- and Ca2+-related stimuli, in agreement with the proposed mode of action of the 2 growth promoters.

Anabolic Agents↗
PubMed2006

Changes in caspase activity during the postmortem conditioning period and its relationship to shear force in porcine longissimus muscle.

The objective of this study was to investigate the protease family caspases in skeletal muscle and their potential contribution to postmortem proteolysis and meat tenderization. Ten Large White gilts were slaughtered, and samples of LM were taken at 0, 2, 4, 8, 16, 32, and 192 h after slaughter and immediately snap frozen in liquid nitrogen. Samples were subsequently analyzed for caspase 3/7 and caspase 9 activity, protein levels of known caspase substrates, alpha II spectrin and poly (ADP-ribose) polymerase (PARP), as well as, at 192 h, shear force. Specific degradation products of alpha II spectrin and PARP, which are known indicators of caspase activity, and apoptosis were detected on immunoblots of muscle samples taken over the postmortem period. The relationships between the changes observed in caspase activities and protein levels of PARP and spectrin across the entire postmortem conditioning period were investigated (n = 70). Protein levels of alpha II spectrin cleavage products across the conditioning period were found to correlate positively to caspase 3/7 activity (r = 0.38, P = 0.003) and caspase 9 activity (r = 0.32, P = 0.012), indicating that caspase-mediated cleavage was occurring in situ. There was a negative relationship between shear force and the 0 to 32 h ratio of caspase 3/7 (r = -0.62, P = 0.053) and caspase 9 activities (r = -0.68, P = 0.044). In addition, there was also a negative relationship between shear force and the level of the caspase-generated alpha II spectrin 120 kDa degradation product (r = -0.75, P = 0.012). The findings of this study indicate that changes in caspase activity and caspase-mediated cleavage take place in muscle during the conditioning period, and this could be associated with the development of tender meat.

Animals↗
PubMed2005

Ontogeny of factors associated with proliferation and differentiation of muscle in the ovine fetus.

The number of muscle fibers within a muscle has been found to be of high importance for the growth potential of an animal, and this number is set during fetal development. The objective of this study was to identify the ontogeny of muscle cell differentiation and fiber formation by observing the changes in expression of factors known to influence myoblast proliferation and differentiation. Twenty-one Swaledale x Leicester Blue Face ewes carrying twins were allotted to this trial. From d 40 of gestation, three ewes were killed every 15 d until term. At each time point, the fetuses were located, removed, and total muscle from both hind limbs was dissected from each fetus and snap frozen in liquid N2. Ribonuclease protection assays were used to quantify transcripts for IGF-I, IGF-II, GH receptor (GHR), and myostatin genes in the muscle samples, whereas quantitative real-time PCR was used to quantify myogenin transcripts. Histological sections also were taken from the fetal muscle samples and observed for evidence of muscle differentiation resulting in fiber formation. The abundance of mRNA for ovine IGF-II and ovine myogenin peaked at d 85 of gestation (P < 0.001). The abundance of ovine IGF-I transcripts peaked at d 100 of gestation, whereas the abundance of ovine GHR mRNA increased throughout gestation (P < 0.05). No change (P = 0.87) in the abundance of myostatin mRNA was observed. The histological sections from the muscle samples demonstrated a clear change in the appearance of the muscle tissue at each time period. Major fiber formation was observed around d 85. The results obtained from the analysis of gene expression and the histological sections suggest that the majority of muscle differentiation and fiber formation takes place around d 85, with myoblast proliferation mainly occurring before this time. It may be possible to manipulate the number of muscle fibers formed by targeting treatments during this proliferation stage immediately before the period of major fiber formation.

Animals↗
PubMed2005

The effect of maternal undernutrition before muscle differentiation on the muscle fiber development of the newborn lamb.

There is a need to improve the lean tissue content of ruminant animals destined for meat production. Muscle fiber number is set during fetal development. The effect of undernutrition of pregnant ewes on subsequent muscle fiber characteristics of their offspring was investigated. The trial involved 32 pregnant ewes carrying twins. The ewes were allocated randomly to one of four groups: three different treatment groups (n = 8) and a control group (n = 8). The diet of the treatment groups was dropped to 50% of their daily requirement to support the ewe and allow for conceptus growth for varying periods before being returned to 100% of their daily requirement until term. Group d 30-70 ewes were fed 100% of their daily requirement until d 30, the diet was then decreased to 50% until d 70; it was then returned to 100% of their daily requirement until term. Group d 55-95 ewes were similarly restricted from d 55 through 95, and Group d 85-115 ewes were restricted from d 85 through 115. The control group was fed 100% of their daily requirement to support the ewe and allow for conceptus growth throughout gestation. After parturition, the lactating ewes were fed a normal commercial diet. On d 14 (after parturition), the lambs were slaughtered and the LM, semitendinosus (ST), and vastus lateralis (VL) were dissected and snap frozen. The immunochemical determination of myosin heavy-chain slow (MHC-slow) and myosin heavy-chain fast (MHC-fast) proteins was measured by immunoprobing of Western blots. The number of fast and slow fibers and the diameter of these fibers also were measured in each muscle sample by histochemical techniques. Decreased maternal nutrition before fiber formation (d 30 through 70) was observed to change the muscle characteristics of the newborn lambs. These lambs had significantly fewer fast fibers (P < 0.001) and significantly more slow fibers (P < 0.001) in both the LM and VL compared with the other groups. Maternal nutrient restriction at the other periods had no effect on the number of muscle fibers in the newborn lambs; however, a decrease (LM, P < 0.05; VL, P < 0.01; ST, P = 0.08) in muscle weight was observed in the lambs born to the ewes restricted between d 85 and 115 of gestation compared with the other groups. This study has shown that decreased maternal diet before muscle fiber formation will alter the muscle fiber development in the fetus.

Animal Feed↗
PubMed2001

Calpastatin expression in porcine cardiac and skeletal muscle and partial gene structure.

The expression in porcine skeletal and cardiac muscle of calpastatin, the specific endogenous inhibitor of the calpain proteolytic system, was examined 16 h after a single dose of a specific beta(2)-agonist. Immunoblotting of extracts indicated that treatment increased skeletal calpastatin 135-kDa band intensity (P < 0.01), while in cardiac combined 145- and 135-kDa band intensity decreased (P < 0.05). Treatment increased skeletal (P < 0.01) but not cardiac calpastatin mRNA steady-state levels. Three types of cardiac calpastatin mRNA transcripts were identified by 5'-RACE. Types I and II encoded a putative XL region that originated either from exon 1x(A) or exon 1x(B), arranged in tandem. Type III predominated in skeletal muscle and originated from exon 1u, which was located 40-50 kb 3' to exons 1x(A) and 1x(B). The region 5' to exon 1u may act as an independent promoter regulated by a cAMP-dependent mechanisms, thereby explaining the differential response of calpastatin to adrenergic stimulation in cardiac and skeletal muscle.

5' Flanking Region↗
PubMed2001

Standardisation of temperature observed by automatic weather stations.

Daily mean, maximum and minimum surface air temperature data were gathered from a network of automatic weather stations (AWS) within the Moor House National Nature Reserve in northern England. Five AWS were installed next to the official Environmental Change Network weather station at Moor House. Data were compared graphically and correction constants were calculated to adjust data from each AWS to the standard of the official station by optimising the concordance correlation coefficient. Each corrected station was re-located next to one of five in-situ stations in and around the reserve, allowing correction of all temperature sensors to a common standard. The mean error associated with measured daily mean, maximum and minimum temperature for each sensor does not exceed +/- 0.2 K. The procedure quantifies a source of systematic measurement error, improving the identification of spatial temperature differences between stations.

Air↗
PubMed2000

Effects of epinephrine infusion on expression of calpastatin in porcine cardiac and skeletal muscle.

beta-Adrenergic agonists induce muscle hypertrophy in mammalian species and alter the extractable activity of calpain proteinase and its specific endogenous inhibitor calpastatin. The effects on skeletal and cardiac muscle calpastatin of continuously infusing a group of pigs for 7 days with the physiological agonist epinephrine (0.15 microg/kg/min) were examined and compared with a placebo group. Basal levels of extractable calpastatin activity were higher in cardiac than skeletal muscle and epinephrine infusion increased the extractable activity in both muscle types (P < 0.05). An anti-recombinant porcine calpastatin antiserum detected a 135-kDa band and a 145/135-kDa doublet on Western blots of skeletal and cardiac extracts, respectively. Epinephrine infusion increased the 135-kDa band in skeletal muscle (P < 0.05), while the ratio of 145/135 kDa in cardiac muscle was decreased (P < 0.05). From Northern blots, the patterns of calpastatin mRNA species were similar in the two muscle types, two major transcripts at 5.8 and 3. 2 kb in cardiac muscle, with equivalent bands in skeletal muscle of 5.4 and 2.8 kb. A faint 7.9-kb band was also detected in skeletal muscle. Epinephrine infusion had no effect on skeletal calpastatin mRNA but tended to increase the 5.8-kb mRNA in cardiac muscle (P = 0. 053). These data indicate a differential response of the two muscle types to mildly elevated plasma epinephrine concentration and the response to elevated epinephrine may be at the translational or posttranslational level. Therefore, this type of stimulus appears to be less effective at perturbing calpastatin gene transcription than certain orally administered synthetic beta-adrenergic agonists.

Animals↗
PubMed1999

Fibre type-specific expression of p94, a skeletal muscle-specific calpain.

Members of the calpain proteinase family are present in all mammalian cells, although a novel calpain 94 kDa isoform is found almost exclusively in skeletal muscle. p94 is difficult to purify from muscle and recombinant p94 autolyses rapidly when expressed in COS cells. However, in vivo the enzyme may be stabilised by interaction with titin, which has two well-characterised binding sites for p94 at the N2- and M-lines. Both these titin subdomains are subject to muscle-specific alternative splicing, which could be related to p94 expression level or stability in muscles of different fibre type. In this study, porcine longissimus dorsi (LD), trapezius (TZ) and adductor longus (AL) were characterised as fast, intermediate and slow using commercially available specific anti-human fast- and slow-myosin heavy chain mAbs and also by conventional histochemistry. p94 was quantified both in whole muscle preparations and single fibres by western blotting using an anti-p94 antiserum generated by expressing a recombinant p94 sequence as a GST fusion protein antigen. SDS PAGE and immunoblotting revealed a single band of approximately 94 kDa with identical mobility in all muscle and fibre preparations. The intensity of the 94 kDa band was greater in LD (22 +/- 1.7 densitometric units mean +/- SEM, n = 3) than TZ and AL (10 +/- 2.3 and 6 +/- 0.9 units, respectively). Expressed as a ratio relative to actin immunoreactivity, p94 is present in all types of single fibres isolated from TZ, but at a significantly lower level (P < 0.01) in slow type I (0.08 +/- 0.01, n = 9), compared to fast IIA/IIB fibres (0.22 +/- 0.02, n = 26). No evidence was seen for rapid or variable rate of p94 degradation in either type of fibre. These data suggest a positive correlation between p94 expression level and fast glycolytic characteristics in porcine muscle.

Animals↗
PubMed1999

Altered calpain levels in longissimus muscle from normal pigs and heterozygotes with the ryanodine receptor mutation.

The calpain proteolytic system was examined in the longissimus muscle (LD) of heterozygote pigs carrying a single copy of a mutation in the skeletal muscle ryanodine receptor gene (RyR1) that is associated with porcine stress syndrome and reduced meat quality. Conventional British White-type pigs (n = 30) were selected from a commercial line on the basis of slaughter weight, backfat depth, and pH at 45 min postmortem > 6.0; based on DNA analysis, 11 were heterozygous RyR1 mutants (Nn), and 19 were normal genotype (NN). The LD samples were taken from carcasses at 2, 4, and 24 h postmortem for calpain analysis with enzyme assay and immunoblotting, using specific antisera raised against recombinant polypeptides derived from calpain large subunits and calpastatin. Shear force (SF) was measured after conditioning for 8 d at 2 degrees C and did not differ between Nn and NN groups. The extractable activity of mu-calpain decreased over 24 h postmortem (P < .001), with no significant difference in activity between NN and Nn animals at any time. The activity of m-calpain also decreased with time (P < .001), but it was lower at all times in Nn than in normal genotypes (P < .001). After Western blotting, the immunoreactivity of mu- and m-calpain large subunit bands declined over 24 h postmortem (P < .001); values for mu-calpain were higher (P < .05) and for m-calpain were lower (P < .001) in heterozygotes than in normal animals at each sampling time. The calpastatin antibody detected a major band of 135 kDa that declined with time postmortem but did not differ between Nn and NN genotypes at any sampling time. These data indicate that the levels of extractable mu- and m-calpain, but not calpastatin, may be different in pigs that carry the RyR1 mutation.

Animals↗
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↗
PubMed1997

Insulin exposure and aging theory.

The underlying mechanism of calorie restriction (CR) extension of mammalian life spans operates by altering the rate of decline in reserve capacity (with time) as well as the exposure to growth stimulus, two mechanisms that seem to be related to the central genetically determined mechanism that controls mammalian life span over a 50-fold range. While genetic control is principally exerted at the level of metabolic rate and entrained protective defenses, CR appears to alter the rate of decline in reserve capacity and the exposure to growth stimulus without appreciable alteration of metabolic rate. CR accomplishes this by lowering the nutritionally driven level of insulin exposure, which in turn lowers overall growth factor exposure, improves age-declining maintenance of mitochondrial maximal function, and maintains a longer-term favorable balance of the insulin:growth hormone antagonism. Obtaining the 'halved' insulin exposure in calorie-restricted animals (relative to ad libitum fed) can be specifically targeted in non-obese ad libitum fed humans by multiple techniques, a situation that may confer most of the life span extension of CR without restricting calories. The prospect for even further extension of the human life span is considered.

Aging↗
PubMed1996

Binding of the cytoplasmic domain of intercellular adhesion molecule-2 (ICAM-2) to alpha-actinin.

Intercellular adhesion molecule-2 (ICAM-2) functions as a ligand for lymphocyte function-associated antigen-1 (LFA-1) and is involved in leukocyte adhesion. We studied intracellular associations of ICAM-2 using a peptide encompassing the cytoplasmic amino acids 231-254 as an affinity matrix. Among the proteins from placental lysates that bound to the peptide was alpha-actinin as demonstrated by immunoblotting. Purified, 125I-labeled alpha-actinin also bound to the peptide. Confocal microscopic analysis of Eahy926 cells demonstrated a colocalization of ICAM-2 and alpha-actinin. Of overlapping octapeptides covering the entire ICAM-2 cytoplasmic amino acids, ICAM-2241-248 bound alpha-actinin most avidly and effectively competed with the longer cytoplasmic peptide for binding. The site of interaction in alpha-actinin was studied using bacterially expressed alpha-actinin fusion proteins. Several constructs covering nonoverlapping regions of alpha-actinin bound to the ICAM-2 cytoplasmic peptide suggesting that multiple regions in alpha-actinin can mediate the interaction. These results, together with previously demonstrated interactions between alpha-actinin and the adhesion proteins ICAM-1, L-selectin, beta1- and beta2-integrins emphasize the role of alpha-actinin as a linker between cell surface adhesion molecules and the actin-containing cytoskeleton.

Actinin↗
PubMed1996

Insulin exposure controls the rate of mammalian aging.

The gradual age-related decline in physiologic function and the late life exponential rise of a diverse group of age-associated diseases are explained by imbalance in specific hormonal axes and cumulative growth factor exposure, respectively. Nutritionally driven 'normal' insulin exposure is central to both cumulative growth factor exposure and imbalance of the insulin-growth hormone axis. Halving normal young adult insulin levels by increased insulin sensitivity may slow the aging process.

Aging↗
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↗
PubMed1995

Are serum levels of vancomycin useful in the first week of therapy?

Controversy exists regarding the need to monitor serum concentrations of vancomycin with some investigators recommending measurement of peak and trough concentrations in the first week of therapy and regularly thereafter, whereas others contend that empiric dosing produces safe and effective drug concentrations so that testing is unnecessary. Since vancomycin concentrations are measured, routinely in our hospital in the first week of therapy, we conducted a 12 month study to assess their clinical value in patients who were treated when gram positive cocci were detected in blood culture smears. One-hundred-five patients had gram positive cocci on blood culture smears. These bacteria were pathogens in 15 patients with Staphylococcus aureus and in 18 with coagulase negative staphylococci based on microbiologic criteria and a chart review confirming their clinical significance. Ten patients with S. aureus and 8 patients with coagulase negative staphylococci that were pathogens and 10 patients with coagulase negative staphylococci that were contaminants were treated with vancomycin. Serum peak and trough concentrations of vancomycin obtained within the first 5 days of therapy in these 28 patients were 14 to 40 micrograms/ml and 4.8 to 20 micrograms/ml. These concentrations were much above the MIC's of the microorganisms (< 4 micrograms/ml). Five patients had increases of serum creatinine of more than 0.6 mg% and in each patient the increases were attributable to other causes-shock, heart failure, and preexisting renal failure. Fifty five peak and trough concentrations 19 of which were drawn in patients with contaminated cultures were measured at a cost of $2,475.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteremia↗