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Introduction: Understanding the genetic mechanisms behind muscle growth and development is crucial for improving the efficiency of animal protein production. Recent poultry studies have identified genes related to muscle development and explored how environmental stressors, such as temperature extremes, affect protein production and meat quality. Non-coding RNAs, including circular RNAs (circRNAs), play crucial roles in modulating gene expression and regulating the translation of mRNAs into proteins. This study examined circRNA expression in turkey skeletal muscle stem cells under thermal stress. The objectives were to identify and quantify circRNAs, assess circRNA abundance following RNAse R depletion, identify differentially expressed circRNAs (DECs), and predict potential microRNA (miRNA) targets for DECs and their associated genes. Materials and methods: Cultured cells from two genetic lines (Nicholas commercial turkey and The Ohio State Random Bred Control 2) under three thermal treatments: cold (33°C), control (38°C), and hot (43°C) were compared at both the proliferation and differentiation stages. CircRNA prediction and differential expression and splicing analyses were conducted using the CIRIquant pipeline for both the untreated and RNase R depletion treated libraries. Predicted interactions between DECs and miRNAs, as well as the potential impact of circRNA secondary structure on these interactions, were investigated. Results: A total of 11,125 circRNAs were predicted within the treatment groups, between both untreated and RNase R treated libraries. Differential expression analyses indicated that circRNA expression was significantly altered by thermal treatments and the genetic background of the stem cells. A total of 140 DECs were identified across the treatment comparisons. In general, more DECs within temperature treatment comparisons were identified in the proliferation stage and more DECs within genetic line comparisons were identified in the differentiation stage. Discussion: This study highlights the significant impact of environmental stressors on non-coding RNAs and their role in gene regulation. Elucidating the role of non-coding RNAs in gene regulation can help further our understanding of muscle development and poultry production, underscoring the broader implications of this research for enhancing animal protein production efficiency. [ABSTRACT FROM AUTHOR]

Skeletal muscle calcium release channel (RYR1) activity by Ca(super.2+) and calmodulin is discussed. Whether the Ca(super.2+)-dependent effects of calmodulin on RYR1 function are caused by Ca(super.2+) binding to calmodulin, RYR1, or both is considered. Ca(super.2+)-free calmodulin has been shown to enhance affinity of RYR1 for Ca. Ca(super.2+) binding to calmodulin changes calmodulin from activator to inhibitor. Ca(super.2+)-binding to RYR1 has been shown to increase its affinity for Ca(super.2+)-free and Ca(super.2+)-bound calmodulin.

A study of skeletal muscle Ca2+ release channel (RyR1) during oxidation showed that some features of the RyR1 sites for binding apocalmodulin are distinct from those of the Ca2+/calmodulin site. Results also revealed that oxidation can change the activity of RyR1 by changing its interaction with calmodulin. Moreover, calmodulin was found to be capable of protecting RyR1 from oxidative modifications during periods of oxidative stress.

Malignant hyperthermia (MH) and the mycotoxin cyclopiazonic acid (CPA) are each associated with abnormal calcium homeostasis in skeletal muscle, a key underlying factor in the development of pale, soft, and exudative (P S E) pork. To determine whether the natural presence of CPA in livestock feed ingredients contributes to the varying incidence of PSE in the pork industry, various levels of CPA (.1 to 50 mg/kg of diet) were included in the diets of market weight hogs (n = 52) of defined malignant hyperthermia genotype (NN = normal, Nn = a MH carrier, and nn = MH-positive). Animals with two copies of the MH mutation (nn) displayed improved live animal performance compared with NN and Nn animals (increased feed intake, average daily gain, and feed efficiency) but yielded lower quality loin chops as indicated by lower 45-min pH (P < .01), higher Commission Internationale de l'Eclairage (CIE) [L.sup.*] color coordinate values (P < .05), and higher drip losses (P < .01). The effects of CPA varied. In the first feeding trial, conducted under normal outside temperatures (2 [degrees] C), CPA had no effect (P > .2) on either live animal performance or meat quality. During the second trial, conducted under extreme outside temperatures (-18 [degrees] C), CPA-dependent reductions (P < .05) in feed intake, average daily gain, and 45-rain pH in nn hogs support the possibility of interactions between malignant hyperthermia and dietary CPA on skeletal muscle calcium homeostasis and the development of PSE pork. These results suggest that this interaction may require stressful environmental conditions or the ingestion of CPA doses much higher than occur under natural conditions. Key Words: Pietrain, Pigs, Cyclopiazonic Acid, Meat Quality

The pharmacokinetic behavior of cyclopiazonic acid (CPA) was determined in market weight pigs using a competitive indirect ELISA developed for the determination of the mycotoxin in various biological matrices. Sample preparation for corn and skeletal muscle was achieved with a single extraction and recoveries of 53 [+ or -] 6% over the effective range of the standard curve. The detection limit of CPA was 1 ppb in plasma, which required no extraction, and 20 ppb in corn and skeletal muscle with average intra- and interassay CV of 11 and 23%, respectively. Levels of CPA contamination in corn grown and stored in Michigan were unremarkable compared with published toxicity thresholds; the highest level of CPA found in any sample was 47 ppb. In pigs given a 20-mg i.v. bolus, CPA distributed rapidly among three compartments, with an overall volume of distribution (49 L) nearly equivalent to total body water. Cyclopiazonic acid was eliminated with a half-life of 24 h. Estimates of these pharmacokinetic parameters were supported by the achievement of steady-state plasma CPA levels within 6 d in pigs consuming a diet containing 10 ppm CPA, and by measured concentrations of CPA in plasma (410 [+ or -] 44 ng/mL) and skeletal muscle (469 [+ or -] 86 ng/g). From these and other data, we concluded that the threat of CPA toxicity to livestock from consumption of cereal grains or to humans from consumption of animal products is minimal. Key Words: Pigs, Cyclopiazonic Acid, ELISA, Pharmacokinetics, Feeds, Tissues

Inorganic phosphate catalyzes the conversion of 3-dehydroshikimic acid (DHS) into gallic acid if molecular oxygen or hydrogen peroxide is present. Other products from the reaction of DHS with oxygen include protocatechuic acid, tricarballylic acid and pyrogallol. Evidence indicated a mechanism involving phosphate-catalyzed tautomerization of DHS to a reactive enediol intermediate. DHS was also observed to have a substantial amount of antioxidant activity relative to alpha-tocopherol, gallic acid, propyl gallate and tert-butylhydroquinone.

Studies on the equilibrating conditions for calmodulin (CaM) binding to the sarcoplasmic reticulum (SR) Ca2+ channel protein reveal that Ca2+ channel protein is the largest CaM receptor. Fluorescence anisotropic studies reveal that CaM has a high affinity for binding to Ca2+ channel protein, regardless of EGTA presence or absence. CaM binding affinity increases on inclusion of CaCu2 and MgCl2.

Abstract Background Skeletal muscle growth and development from embryo to adult consists of a series of carefully regulated changes in gene expression. Understanding these developmental changes in agriculturally important species is essential to the production of high quality meat products. For example, consumer demand for lean, inexpensive meat products has driven the turkey industry to unprecedented production through intensive genetic selection. However, achievements of increased body weight and muscle mass have been countered by an increased incidence of myopathies and meat quality defects. In a previous study, we developed and validated a turkey skeletal muscle-specific microarray as a tool for functional genomics studies. The goals of the current study were to utilize this microarray to elucidate functional pathways of genes responsible for key events in turkey skeletal muscle development and to compare differences in gene expression between two genetic lines of turkeys. To achieve these goals, skeletal muscle samples were collected at three critical stages in muscle development: 18d embryo (hyperplasia), 1d post-hatch (shift from myoblast-mediated growth to satellite cell-modulated growth by hypertrophy), and 16wk (market age) from two genetic lines: a randombred control line (RBC2) maintained without selection pressure, and a line (F) selected from the RBC2 line for increased 16wk body weight. Array hybridizations were performed in two experiments: Experiment 1 directly compared the developmental stages within genetic line, while Experiment 2 directly compared the two lines within each developmental stage. Results A total of 3474 genes were differentially expressed (false discovery rate; FDR < 0.001) by overall effect of development, while 16 genes were differentially expressed (FDR < 0.10) by overall effect of genetic line. Ingenuity Pathways Analysis was used to group annotated genes into networks, functions, and canonical pathways. The expression of 28 genes involved in extracellular matrix regulation, cell death/apoptosis, and calcium signaling/muscle function, as well as genes with miscellaneous function was confirmed by qPCR. Conclusions The current study identified gene pathways and uncovered novel genes important in turkey muscle growth and development. Future experiments will focus further on several of these candidate genes and the expression and mechanism of action of their protein products.

Differential [Ca.sup.2+] sensitivity of skeletal and cardiac muscle ryanodine receptors in the presence of calmodulin. Am J Physiol Cell Physiol 279: C724-C733, 2000.--Calmodulin (CaM) activates the skeletal muscle ryanodine receptor [Ca.sup.2+] release channel (RyR1) in the presence of nanomolar [Ca.sup.2+] concentrations. However, the role of CaM activation in the mechanisms that control [Ca.sup.2+] release from the sarcoplasmic reticulum (SR) in skeletal muscle and in the heart remains unclear. In media that contained 100 nM [Ca.sup.2+], the rate of [sup.45][Ca.sup.2+] release from porcine skeletal muscle SR vesicles was increased approximately threefold in the presence of CaM (1 [micro]M). In contrast, cardiac SR vesicle [sup.45][Ca.sup.2+] release was unaffected by CaM, suggesting that CaM activated the skeletal RyR1 but not the cardiac RyR2 channel isoform. The activation of RyR1 by CaM was associated with an approximately sixfold increase in the [Ca.sup.2+] sensitivity of [[sup.3]H]ryanodine binding to skeletal muscle SR, whereas the [Ca.sup.2+] sensitivity of cardiac SR [[sup.3]H]ryanodine binding was similar in the absence and presence of CaM. Cross-linking experiments identified both RyR1 and RyR2 as predominant CaM binding proteins in skeletal and cardiac SR, respectively, and [[sup.35]S]CaM binding determinations further indicated comparable CaM binding to the two isoforms in the presence of micromolar [Ca.sup.2+]. In nanomolar [Ca.sup.2+], however, the affinity and stoichiometry of RyR2 [[sup.35]S]CaM binding was reduced compared with that of RyR1. Together, our results indicate that CaM activates RyR1 by increasing the [Ca.sup.2+] sensitivity of the channel, and further suggest differences in CaM's functional interactions with the RyR1 and RyR2 isoforms that may potentially contribute to differences in the [Ca.sup.2+] dependence of channel activation in skeletal and cardiac muscle. sarcoplasmic reticulum; calcium release channel; excitation-contraction coupling

Ferric orthophosphate (FePO4) has had limited use as an iron fortificant in ready-to-eat (RTE) cereal because of its variable bioavailability, the mechanism of which is poorly understood. Even though FePO4 has desirable sensory properties as compared to other affordable iron fortificants, few published studies have well-characterized its physicochemical properties. Semi-crystalline materials such as FePO4 have varying degrees of molecular disorder, referred to as amorphous content, which is hypothesized to be an important factor in bioavailability. The objective of this study was to systematically measure the physicochemical factors of particle size, surface area, amorphous content, and solubility underlying the variation in FePO4 bioavailability. Five commercial FePO4 sources and ferrous sulfate were added to individual batches of RTE cereal. The relative bioavailability value (RBV) of each iron source, determined using the AOAC Rat Hemoglobin Repletion Bioassay, ranged from 51% to 99% (p < 0.05), which is higher than typically reported. Solubility in dilute HCl accurately predicted RBV (R2 = 0.93, p = 0.008). Amorphous content measured by Dynamic Vapor Sorption ranged from 1.7% to 23.8% and was a better determinant of solubility (R2 = 0.91; p = 0.0002) than surface area (R2 = 0.83; p = 0.002) and median particle size (R2 = 0.59; p = 0.12). The results indicate that while solubility of FePO4 is highly predictive of RBV, solubility, in turn, is strongly linked to amorphous content and surface area. This information may prove useful for the production of FePO4 with the desired RBV. [ABSTRACT FROM AUTHOR]