Intact Muscle Tissue Research Articles

Current Methodologies for Inducing Aligned Myofibers in Tissue Constructs for Skeletal Muscle Tissue Regeneration.

Significance: Volumetric muscle loss (VML) results in the loss of large amounts of tissue that inhibits muscle regeneration. Existing therapies, such as autologous muscle transfer and physical therapy, are incapable of returning full function and force production to injured muscle. Recent Advances: Skeletal muscle tissue constructs may provide an alternative to existing therapies currently used to treat VML. Unlike autologous muscle transplants, muscle constructs can be cultured in vitro and are not reliant on intact muscle tissue. Skeletal muscle constructs can be generated from small muscle biopsies and could be used to generate skeletal muscle tissue constructs to replace injured tissues. Critical Issues: To serve as effective therapies, muscle constructs must be capable of generating contractile forces that can assist the function of host skeletal muscle. The contractile force of native muscle arises in part as a consequence of the highly aligned, bundled architecture of myofibers. Attempts to induce similar alignment include applications of tension/strain across hydrogels, inducing aligned architectures within scaffolds, casting tissues in straited molds, and 3D printing. While all these methods have demonstrated efficacy toward inducing myofiber alignment, the extent of myofiber alignment, tissue formation, and force production varies. This manusript critically reviews the advantages and limitations of these methods and specifically discusses their ability to impart mechanical and architectural cues to induce alignment within tissue constructs. Future Directions: As tissue-synthesizing techniques continue to improve, muscle constructs must include more cell types than simply myoblasts, such as the addition of neuronal and endothelial cells. Higher-level tissue organization is critical to the success of these constructs. Many of these technologies have yet to be implanted into host tissue to understand engraftment and how they can contribute to traumatic injury, and as such continued collaboration between surgeons and tissue engineers is necessary to ultimately result in clinical translation.

Influence of muscle type and microstructure on iridescence in cooked, cured pork meat products.

Microstructural factors associated with surface iridescence in cooked, cured pork products were investigated. Meat iridescence is a commonly observed physical phenomenon in raw meat and meat products that consist of intact muscle tissue. Since the purchase decision of consumers is mainly driven by the first impression of meat color and appearance, products showing colorful iridescence may be rejected. Four different muscles (RF: M. rectus femoris, BF: M. biceps femoris, ST: M. semitendinosus, and LD: M. longissimus thoracis et lumborum) were brine-injected, cooked, sliced, and iridescence was evaluated by digital image analysis and sensory analysis. Sarcomere lengths, fiber diameters, and surface microstructure were analyzed in iridescent and noniridescent sections. Highest iridescence extent by image analysis was found in LD (37.3± 16.4%), and highest overall iridescence score (extent and intensity, 6.11± 1.78) was observed in BF. Sarcomere lengths did not differ significantly between iridescent (1.05± 0.09µm LD) and noniridescent areas (1.08± 0.94µm LD) within muscles (p>0.05). Iridescent sections showed smooth and ordered surface structures with cross-sectioned myofibers, whereas in noniridescent sections, surfaces were more unstructured and myofibers obliquely cut. The results of the study indicate that the sarcomere length and fiber diameters may thus be only of minor importance for the explanation of meat iridescence in cooked meat products and are rather related to multiple scattering and absorption effects on smaller structural entities such as the myofilament lattice or larger entities such as fiber bundles. PRACTICAL APPLICATION: Iridescence can be a problem for the meat industry due to consumers concerns about green-iridescent colors in meat. The underlying mechanisms and structures have not yet been fully clarified, and thus no practical solutions to eliminate iridescence have been found so far. This research presents new insights into the structural attributes that are interrelated with meat iridescence and shows that iridescence is rather influenced by cutting angle of muscle fibers and surface homogeneity than by muscle fiber diameters or sarcomere lengths. This should be considered by the industry when seeking for ways to reduce the potential problem of iridescence.

Myosin cross-bridge kinetics slow at longer muscle lengths during isometric contractions in intact soleus from mice.

Muscle contraction results from force-generating cross-bridge interactions between myosin and actin. Cross-bridge cycling kinetics underlie fundamental contractile properties, such as active force production and energy utilization. Factors that influence cross-bridge kinetics at the molecular level propagate through the sarcomeres, cells and tissue to modulate whole-muscle function. Conversely, movement and changes in the muscle length can influence cross-bridge kinetics on the molecular level. Reduced, single-molecule and single-fibre experiments have shown that increasing the strain on cross-bridges may slow their cycling rate and prolong their attachment duration. However, whether these strain-dependent cycling mechanisms persist in the intact muscle tissue, which encompasses more complex organization and passive elements, remains unclear. To investigate this multi-scale relationship, we adapted traditional step-stretch protocols for use with mouse soleus muscle during isometric tetanic contractions, enabling novel estimates of length-dependent cross-bridge kinetics in the intact skeletal muscle. Compared to rates at the optimal muscle length (Lo), we found that cross-bridge detachment rates increased by approximately 20% at 90% of Lo (shorter) and decreased by approximately 20% at 110% of Lo (longer). These data indicate that cross-bridge kinetics vary with whole-muscle length during intact, isometric contraction, which could intrinsically modulate force generation and energetics, and suggests a multi-scale feedback pathway between whole-muscle function and cross-bridge activity.

Muscle-derived exosomes encapsulate myomiRs and are involved in local skeletal muscle tissue communication.

Exosomes are extracellular vesicles that are released from most cell types encapsulating specific molecular cargo. Exosomes serve as mediators of cell-to-cell and tissue-to-tissue communications under normal and pathological conditions. It has been shown that exosomes carrying muscle-specific miRNAs, myomiRs, are secreted from skeletal muscle cells in vitro and are elevated in the blood of muscle disease patients. The aim of this study was to investigate the secretion of exosomes encapsulating the four myomiRs from skeletal muscle tissues and to assess their role in inter-tissue communication between neighboring skeletal muscles in vivo. We demonstrate, for the first time, that isolated, intact skeletal muscle tissues secrete exosomes encapsulating the four myomiRs, miR-1, miR-133a, miR-133b, and miR-206. Notably, we show that the sorting of the four myomiRs within exosomes varies between skeletal muscles of different muscle fiber-type composition. miR-133a and miR-133b downregulation in TA muscles caused a reduction of their levels in neighboring skeletal muscles and in serum exosomes. In conclusion, our results reveal that skeletal muscle-derived exosomes encapsulate the four myomiRs, some of which enter the blood, while a portion is used for the local communication between proximal muscle tissues. These findings provide important evidence regarding novel pathways implicated in skeletal muscle function.

Direct measurement of the direction-dependent mechanical behaviour of skeletal muscle extracellular matrix

This paper reports the first comprehensive data set on the anisotropic mechanical properties of isolated endo- and perimysial extracellular matrix of skeletal muscle, and presents the corresponding protocols for preparing and testing the samples. In particular, decellularisation of porcine skeletal muscle is achieved with caustic soda solution, and mechanical parameters are defined based on compressive and tensile testing in order to identify the optimal treatment time such that muscle fibres are dissolved whereas the extracellular matrix remains largely intact and mechanically functional. At around 18 h, a time window was found and confirmed by histology, in which axial tensile experiments were performed to characterise the direction-dependent mechanical response of the extracellular matrix samples, and the effect of lateral pre-compression was studied. The typical, large variability in the experimental stress response could be largely reduced by varying a single scalar factor, which was attributed to the variation of the fraction of extracellular matrix within the tissue. While experimental results on the mechanical properties of intact muscle tissue and single muscle fibres are increasingly available in literature, there is a lack of information on the properties of the collagenous components of skeletal muscle. The present work aims at closing this gap and thus contributes to an improved understanding of the mechanics of skeletal muscle tissue and provides a missing piece of information for the development of corresponding constitutive and computational models.

Muscle water properties in raw intact broiler breast fillets with the woody breast condition

The purpose of this study was to investigate the relationships between muscle water properties, water-holding capacity (WHC), and woody breast (WB) severity in intact raw broiler breast fillets. Broiler pectoralis major deboned at 3 h postmortem was collected from a commercial plant and categorized as normal (NORM), moderate WB, or severe WB (SEV). Meat drip loss was calculated based on weight loss during overnight storage at 4°C. Water properties of the intact fillets were determined with time domain nuclear magnetic resonance and the T2 relaxation times were determined using an inverse Laplace algorithm (CONTIN). Three T2 water components, hydration water (T2b), intra-myofibrillar water (T21), and extra-myofibrillar water (T22), were identified. With increasing WB severity, the time constant of each water component and the relative content of T22 (P22) increased while the relative areas of T2b and T21 (P2b and P21, respectively) decreased. Spearman correlation analysis showed that there were significant correlations between the WB condition score and either the time constant or normalized area for each T2 component. T22 normalized areas (A22) were most strongly correlated with the WB score (r = 0.75); however, the weakest correlation was found between the WB score and T21 areas (A21). Pearson correlation analysis revealed that the strongest correlation (r = 0.64) was found between A22 and drip loss; however, there was no correlation between A21 and drip loss. Within the NORM group, drip loss was significantly correlated to the time constants for both T2b and T21. Within the SEV group, only A22 was significantly correlated to drip loss. These data indicate that the WB condition has a significant impact on the distribution of water within the intact muscle tissue. The content of extra-myofibrillar water in broiler breast fillets may be a key factor responsible for the poor WHC measurements in WB meat.

High resolution ultrasound for imaging complications of muscle injury: Is there an additional role for elastography?

Muscle healing after injury occurs within a period of weeks following a three-phase physiological process. Disruption of the normal healing process may lead to a number of complications, including excessive scar formation, myositis ossificans, muscle atrophy, muscle cysts and hernias. Complications of muscle injury are important because they may be symptomatic, are associated with high risk of re-injury and compromise muscle performance, thus delaying return to sporting activity and requiring special treatment. High-resolution ultrasound imaging equipped with high-frequency probes and advanced B-mode and Doppler technology has emerged as a promising modality for the diagnosis, grading and follow-up of muscle injury. Ultrasound allows imaging of minimal scar formation, early detection of myositis ossificans and cysts, and dynamic evaluation of small muscle hernias. Ultrasound imaging combined with strain and shear wave elastography can also provide information on the mechanical properties of intact and diseased muscle tissue, thus allowing assessment of muscle biomechanics in the clinical setting. This article reviews the histology and ultrasound appearance of normal and abnormal muscle healing with an emphasis on the sonographic appearances of muscle injury complications. It also discusses pitfalls, provides tips for an less experienced sonographer and presents the possible role of strain elastography in the diagnosis of complications, such as scar tissue.

Quantitative in situ proximity ligation assays examining protein interactions and phosphorylation during smooth muscle contractions

Antibody-based in situ proximity ligation assays (isPLA) have the potential to study protein phosphorylation and protein interactions with spatial resolution in intact tissues. However, the application of isPLA at the tissue level is limited by a lack of appropriate positive and negative controls and the difficulty in accounting for changes in tissue shape. Here we demonstrate a set of experimental and computational approaches using gastric fundus smooth muscles to improve the validity of quantitative isPLA. Appropriate positive and negative biological controls and PLA technical controls were selected to ensure experimental rigor. To account for changes in morphology between relaxed and contracted smooth muscles, target PLA spots were normalized to smooth muscle myosin light chain 20 PLA spots or the cellular cross-sectional areas. We describe the computational steps necessary to filter out false-positive improperly sized spots and set the thresholds for counting true positive PLA spots to quantify the PLA signals. We tested our approach by examining protein phosphorylation and protein interactions in smooth muscle myofilament Ca2+ sensitization pathways from resting and contracted gastric fundus smooth muscles. In conclusion, our tissue-level isPLA method enables unbiased quantitation of protein phosphorylation and protein-protein interactions in intact smooth muscle tissues, suggesting the potential for quantitative isPLA applications in other types of intact tissues.

Exploring the antivirulent and sea food preservation efficacy of essential oil combined with DNase on Vibrio parahaemolyticus

Vibrio parahaemolyticus is a predominant aquaculture pathogen causing food borne infections through the consumption of raw or undercooked sea foods. Biofilm formation and quorum sensing mediated virulence factors play a pivotal role in mediating these infections. The present study evaluates the antibiofilm and anti-quorum sensing potential of an unexplored essential oil (EO) and its major compounds (cinnamaldehyde and linalool) against V. parahaemolyticus. Furthermore, the synergistic effects of the EO along with a commercial available DNase I and marine bacterial DNase (MBD) were explored for its antibiofilm efficacy. In addition, the food preservative efficacy of linalool and cinnamaldehyde were evaluated in prawns (a sea-food model) infected with V. parahaemolyticus stored at 28 °C and 4 °C. The treated prawns showed reduced bacterial load and exhibited minimum lipid peroxidation. Scanning Electron Microscopy (SEM) revealed the intact muscle tissues of the treated samples which indicate that the EO components did not damage the prawn tissues. The results revealed that the individual EO components has good efficacy equal to that of the standard food preservative sodium benzoate. This study shows that the synergistic action of EO and DNases might offer an alternate strategy for sea food preservation.

Some Peculiarities of Local Distribution of Multipotent Mesenchymal Stromal Cells after Their Injection into Intact Muscle Tissue in Experiment.

Changes in the muscular tissue after subcutaneous injection of autologous bone marrow multipotent mesenchymal stromal cells transfected with GFP gene and additionally stained with cell membrane dye Vybrant CM-Dil in the projection of ligated femoral vein were studied by light microscopy with luminescence. Stromal cells injected through the skin can appear not only in the damaged tissue where acceleration of regeneration processes is required, but also in intact structures located in superficial or deeper layers. In intact muscular tissue, stromal cells spreading in the perivascular tissue initiate inflammation and migration of macrophages, activate and even trigger sclerotic processes due to differentiation into connective tissue cells (fibroblasts) and stimulation of proliferation and collagen synthesis by host fibroblasts. Injected multipotent mesenchymal stromal cells are gradually phagocytized by macrophages.

Analysis of Aerobic Respiration in Intact Skeletal Muscle Tissue by Microplate-Based Respirometry.

Mitochondrial function is a key component of skeletal muscle health, and its dysfunction has been associated with a wide variety of diseases. Microplate-based respirometry measures aerobic respiration of live cells through extracellular changes in oxygen concentration. Here, we describe a methodology to measure aerobic respiration of intact murine skeletal muscle tissue. The tissues are not cultured, permeabilized, or enzymatically dissociated to single fibers, so there is minimal experimental manipulation affecting the samples prior to acquiring measurements.

Usage of the ultrafast intermolecular single-quantum coherence (UF iSQC) sequence for NMR spectroscopy of ex vivo tissue

High-resolution nuclear magnetic resonance (NMR) spectroscopy has been considered as a powerful tool for noninvasive, rapid, and accurate composition analyses on solution samples. However, because tissues are in semisolid phase, the high-resolution spectra cannot be obtained by conventional NMR spectroscopy. In the present study, an ultrafast intermolecular single quantum coherence (UF iSQC) NMR spectroscopic method based on spatial encoding is used for direct analyses of intact salmon muscle tissues, intact eggs from shishamo smelt, and a whole zebra fish. Most of free amino acid and fatty acid signals can be directly detected within 5min in their original state without tedious sample preparation processes. The experimental results show that not only can the UF iSQC method overcome the inhomogeneity of biological tissues, but also it can greatly reduce experimental times owing to the introduction of ultrafast acquisition schemes. Changes occurring in amino acids and fatty acids of salmon muscle tissues, eggs from shishamo smelt, and the whole zebra fish during storage are investigated. Similar variation patterns of metabolic profiles have been deduced for three fish samples, yielding good agreements with literature results.

Effects of nanosized lithium carbonate particles on intact muscle tissue and tumor growth.

The effects of nanosized lithium carbonate particles on muscle tissue structure and development of experimental hepatocarcinoma-29 transplanted into the hip were studied in CBA mice. Necrotic changes in all structural components of the muscle were detected after intramuscular injection of nanosized lithium carbonate particles to intact animals. Regeneration of the muscle fibers after lithium carbonate treatment was associated with a significant increase in macrophage count, number of microvessels, activation of fibroblasts, and complete recovery of the organ structure. Injection of lithium carbonate nanoparticles at the periphery of tumor growth caused tumor cell necrosis, destruction of the vascular bed, and attraction of neutrophils and macrophages to the tumor focus. After the preparation was discontinued, the tumor developed with lesser number of vessels, smaller tumor cells, and lesser deformation of the cell nuclei structure.

High-Resolution 1H NMR Spectroscopy of Fish Muscle, Eggs and Small Whole Fish via Hadamard-Encoded Intermolecular Multiple-Quantum Coherence

Background and PurposeNuclear magnetic resonance (NMR) spectroscopy has become an important technique for tissue studies. Since tissues are in semisolid-state, their high-resolution (HR) spectra cannot be obtained by conventional NMR spectroscopy. Because of this restriction, extraction and high-resolution magic angle spinning (HR MAS) are widely applied for HR NMR spectra of tissues. However, both of the methods are subject to limitations. In this study, the feasibility of HR 1H NMR spectroscopy based on intermolecular multiple-quantum coherence (iMQC) technique is explored using fish muscle, fish eggs, and a whole fish as examples.Materials and MethodsIntact salmon muscle tissues, intact eggs from shishamo smelt and a whole fish (Siamese algae eater) are studied by using conventional 1D one-pulse sequence, Hadamard-encoded iMQC sequence, and HR MAS.ResultsWhen we use the conventional 1D one-pulse sequence, hardly any useful spectral information can be obtained due to the severe field inhomogeneity. By contrast, HR NMR spectra can be obtained in a short period of time by using the Hadamard-encoded iMQC method without shimming. Most signals from fatty acids and small metabolites can be observed. Compared to HR MAS, the iMQC method is non-invasive, but the resolution and the sensitivity of resulting spectra are not as high as those of HR MAS spectra.ConclusionDue to the immunity to field inhomogeneity, the iMQC technique can be a proper supplement to HR MAS, and it provides an alternative for the investigation in cases with field distortions and with samples unsuitable for spinning. The acquisition time of the proposed method is greatly reduced by introduction of the Hadamard-encoded technique, in comparison with that of conventional iMQC method.

Amino acid mutations in the caldesmon COOH-terminal functional domain increase force generation in bladder smooth muscle

Caldesmon (CaD), a component of smooth muscle thin filaments, binds actin, tropomyosin, calmodulin, and myosin and inhibits actin-activated ATP hydrolysis by smooth muscle myosin. Internal deletions of the chicken CaD functional domain that spans from amino acids (aa) 718 to 731, which corresponds to aa 512-530 including the adjacent aa sequence in mouse CaD, lead to diminished CaD-induced inhibition of actin-activated ATP hydrolysis by myosin. Transgenic mice with mutations of five aa residues (Lys(523) to Gln, Val(524) to Leu, Ser(526) to Thr, Pro(527) to Cys, and Lys(529) to Ser), which encompass the ATPase inhibitory determinants located in exon 12, were generated by homologous recombination. Homozygous (-/-) animals did not develop, but heterozygous (+/-) mice carrying the expected mutations in the CaD ATPase inhibitory domain (CaD mutant) matured and reproduced normally. The peak force produced in response to KCl and electrical field stimulation by the detrusor smooth muscle from the CaD mutant was high compared with that of the wild type. CaD mutant mice revealed nonvoiding contractions during bladder filling on awake cystometry, suggesting that the CaD ATPase inhibitory domain suppresses force generation during the filling phase and this suppression is partially released by mutations in 50% of CaD in heterozygous. Our data show for the first time a functional phenotype, at the intact smooth muscle tissue and in vivo organ levels, following mutation of a functional domain at the COOH-terminal region of CaD.

Myopathic lamin mutations impair nuclear stability in cells and tissue and disrupt nucleo-cytoskeletal coupling

Lamins are intermediate filament proteins that assemble into a meshwork underneath the inner nuclear membrane, the nuclear lamina. Mutations in the LMNA gene, encoding lamins A and C, cause a variety of diseases collectively called laminopathies. The disease mechanism for these diverse conditions is not well understood. Since lamins A and C are fundamental determinants of nuclear structure and stability, we tested whether defects in nuclear mechanics could contribute to the disease development, especially in laminopathies affecting mechanically stressed tissue such as muscle. Using skin fibroblasts from laminopathy patients and lamin A/C-deficient mouse embryonic fibroblasts stably expressing a broad panel of laminopathic lamin A mutations, we found that several mutations associated with muscular dystrophy and dilated cardiomyopathy resulted in more deformable nuclei; in contrast, lamin mutants responsible for diseases without muscular phenotypes did not alter nuclear deformability. We confirmed our results in intact muscle tissue, demonstrating that nuclei of transgenic Drosophila melanogaster muscle expressing myopathic lamin mutations deformed more under applied strain than controls. In vivo and in vitro studies indicated that the loss of nuclear stiffness resulted from impaired assembly of mutant lamins into the nuclear lamina. Although only a subset of lamin mutations associated with muscular diseases caused increased nuclear deformability, almost all mutations tested had defects in force transmission between the nucleus and cytoskeleton. In conclusion, our results indicate that although defective nuclear stability may play a role in the development of muscle diseases, other factors, such as impaired nucleo-cytoskeletal coupling, likely contribute to the muscle phenotype.

Connective Tissue in Gut Development: A Key Player in Motility and in Intestinal Desmosis

Efficient intestinal peristalsis is a function of intact enteric nervous system, muscle, and connective muscularis propria tissue. Malfunction of any component results in impaired peristalsis. Hirschsprung disease (HD) as prototypic enteric neural migration disorder is increasingly well characterized. More recently, intestinal myopathies and particularly defects of myenteric collagenization have entered the focus of attention. However, detailed development of muscularis propria connective tissue is not well known. The aim of this study was to morphologically characterize intestinal connective tissue in fetal and postnatal development and intestinal pseudo-obstruction. In this study, 130 archival specimens of fetal autopsies, intestinal resections, and biopsies were analyzed. Patients' age was 10th gestational week (gw) to 70 years. Muscularis mucosae, muscle layers, collagen tissue, and enteric plexus were analyzed. Picrosirius red stains, enzyme histochemistry, and immunohistochemistry for collagens I, III, and IV were performed. Total 89 normal intestinal specimens were from fetal autopsies or intestinal resections; 41 patients showed a primary structural colon wall defect (HD, desmosis). Our results showed a constant increase in tunica muscularis propria thickness with age. Separation into circular and longitudinal muscle layer first occurred in the 11th gw. A tendinous collagen plexus layer first arose in the 10th gw and showed a steady caliber increase. Muscularis mucosae first appeared in the 10th gw and grew independent of any primary gastrointestinal disease. In the 11th gw, enteric ganglia were fully developed. In desmosis, a collagen plexus layer was absent. In contrast, in HD, muscularis mucosae showed hypertrophy, but the collagen plexus layer was intact in the aganglionic segment. In intestinal neuronal dysplasia and hypoganglionosis, nerve cell development was disturbed; connective tissue and muscle layers were well developed. Our comprehensive study of intestinal connective tissue development in comparison to neural intestinal wall components in normal and pathological conditions showed that tendinous tissue develops parallel to muscularis propria and arises early in embryogenesis. In enteric nervous system disorders, ganglionic lesions develop independently of impaired collagen network, whereas mucosal biopsies serve for diagnosis of HD, seromuscular biopsies are required to prove desmosis in gastrointestinal dysmotility disorders.

Effects of combined hormone replacement therapy or its effective agents on the IGF-1 pathway in skeletal muscle

Objectives To investigate the effects of combined hormone replacement therapy (HRT) and its effective agents on the IGF-1 signaling pathway. Design and methods To examine the effects of HRT on skeletal muscle in vivo, we utilized pre- and post-intervention samples from a randomized double blinded trial with 50–57-year-old women. The intervention included the year-long use of either HRT preparation (2 mg 17β-estradiol, E 2; 1 mg norethisterone acetate, NETA, n = 10) or placebo (CO, n = 9). Microarray technology and quantitative PCR (qPCR) were used to study the expression of insulin-like growth factor I ( IGF-1) and its splice variants as well as IGF-1 receptor, Akt1, mTOR, FOXO1, FOXO3, atrogin, estrogen receptors and androgen receptor in muscle samples. Serum concentrations of IGF-1, E 2 and testosterone were measured. C2C12 myotubes were fed with E 2 or NETA followed by analyzing the expression of essentially the same gene transcripts as in human samples by qPCR and phosphorylation of Akt and mTOR by Western blotting. Results The gene expression of IGF-1 and its splice variant, IGF-1Ec (also known as the mechano growth factor or MGF), mTOR, FOXO3, and AR was up-regulated among the HRT users compared to the CO (P < 0.05), while Akt1 was down-regulated (P < 0.05). The change in the level of IGF-1Ec transcript correlated positively with muscle size at post-intervention (r = 0.5, P < 0.05). In C2C12 myotubes, no statistically significant effects of either E 2 or NETA at the level of gene transcripts studied were identified. The amount of phosphorylated Akt appeared to respond to NETA, albeit the response was not statistically significant. Phosphorylation of mTOR did not respond to either of the treatments. Conclusion Year-long postmenopausal HRT was found to affect the expression of the genes along the IGF-1 signaling cascade reflecting the higher muscle mass compared to the CO women. By using cell culture model we were, however, unable to confirm the possible differential role of E 2 and NETA. It appears that the synchronous presence of both effective agents of the HRT or the presence of yet unidentified microenvironmental factors providing proper paracrine signals naturally existing in the intact muscle tissue is critical for appropriate signaling via sex steroid-IGF-1 axis to occur.

Detection of Gunshot Primer Residue on Bone in an Experimental Setting—An Unexpected Finding*

Pork ribs with intact muscle tissue were used in an experimental attempt to identify bullet wipe on bone at distances from 1 to 6 feet with 0.45 caliber, full metal jacket ammunition. This resulted in the unexpected finding of primer-derived gunshot residue (GSR) deep within the wound tract. Of significance is the fact that the GSR was deposited on the bone, under the periosteum, after the bullet passed through a Ziploc bag and c. 1 inch of muscle tissue. It is also important to note that the GSR persisted on the bone after the periosteum was forcibly removed. The presence of primer-derived GSR on bone provides the potential to differentiate gunshot trauma from blunt trauma when the bone presents an atypical gunshot wound. In this study, the presence of gunshot primer residue at a distance of 6 feet demonstrates the potential for establishing maximum gun-to-target distance for remote shootings.

Postmortem proteome degradation profiles of longissimus muscle in Yorkshire and Duroc pigs and their relationship with pork quality traits

Conversion of muscle to meat is regulated by complex interactions of biochemical processes that take place during postmortem storage of the carcass. Enzymatic proteolysis, among other postmortem biochemical phenomena; e.g. glycolysis; changes tough intact muscle tissue into more tender meat. Knowledge on proteome-wide proteolysis of muscle tissue in relation to meat quality is limited and potential breed-specific differences have received little attention. Therefore, we investigated meat quality traits and proteolysis profiles of the longissimus proteome of five Yorkshire and five Duroc pigs at slaughter and after 1, 2, 3, 7, and 10 days of ageing. Drip loss increased with ageing while cooking loss was unchanged in both breeds. Shear force varied between animals and decreased with ageing. Analysis of the proteomes showed four types of temporal expression profiles. Association analysis suggested several potential protein biomarkers for drip loss and shear force in both breeds, but none for cooking loss.