Rabbit Muscle Research Articles

Different activation of MAPKs and Akt/GSK3β after preload vs. afterload elevation.

AimsPressure overload (PO) and volume overload (VO) lead to concentric or eccentric hypertrophy. Previously, we could show that activation of signalling cascades differ in in vivo mouse models. Activation of these signal cascades could either be induced by intrinsic load sensing or neuro‐endocrine substances like catecholamines or the renin‐angiotensin‐aldosterone system.Methods and resultsWe therefore analysed the activation of classical cardiac signal pathways [mitogen‐activated protein kinases (MAPKs) (ERK, p38, and JNK) and Akt‐GSK3β] in in vitro of mechanical overload (ejecting heart model, rabbit and human isolated muscle strips). Selective elevation of preload in vitro increased AKT and GSK3β phosphorylation after 15 min in isolated rabbit muscles strips (AKT 49%, GSK3β 26%, P < 0.05) and in mouse ejecting hearts (AKT 51%, GSK49%, P < 0.05), whereas phosphorylation of MAPKs was not influenced by increased preload. Selective elevation of afterload revealed an increase in ERK phosphorylation in the ejecting heart (43%, P < 0.05), but not in AKT, GSK3β, and the other MAPKs. Elevation of preload and afterload in the ejecting heart induced a significant phosphorylation of ERK (95%, P < 0.001) and showed a moderate increased AKT (P = 0.14) and GSK3β (P = 0.21) phosphorylation, which did not reach significance. Preload and afterload elevation in muscles strips from human failing hearts showed neither AKT nor ERK phosphorylation changes.ConclusionsOur data show that preload activates the AKT–GSK3β and afterload the ERK pathway in vitro, indicating an intrinsic mechanism independent of endocrine signalling.

Formation and physicochemical properties of glycogen phosphorylase in complex with a cationic polyelectrolyte

The accumulation of rabbit muscle glycogen phosphorylase b (RMGPb) in electrostatic complexes with the cationic polyelectrolyte poly 2-(dimethylamino) ethyl methacrylate in its quenched form (QPDMAEMA) was studied in two buffer solutions. In the N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES) buffer, large complexes of RMGPb-QPDMAEMA were formed which adopted smaller sizes as QPDMAEMA concentration increased. However, in N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid) (HEPES) buffer, the hydrodynamic radius of the formed complexes gradually increased as the polymer concentration increased. Zeta potential measurements (ζp) showed that RMGPb significantly changed the ζp of the QPDMAEMA aggregates. Fluorescence studies showed that the interaction between RMGPb and QPDMAEAMA was enhanced as polymer concentration increased. Specifically, 8-anilinonaphthalene-1-sulfonic acid (ANS) fluorescence indicated that in the BES buffer the aggregates became denser as more QPDMAEMA was added, while in the HEPES buffer the density of the formed structures decreased. RMGPb's secondary structure was examined by Attenuated Total Reflection - Fourier Transform Infrared (ATR-FTIR) and Circular Dichroism (CD) showing that QPDMAEMA interaction with RMGPb does not induce any changes to the secondary structure of the enzyme. These observations suggest that cationic polyelectrolytes may be utilized for the formulation of RMGPb in multifunctional nanostructures and be further exploited in innovative biotechnology applications and bioinspired materials development.

Microvascular Permeability and Texture Analysis of the Skeletal Muscle of Diabetic Rabbits With Critical Limb Ischaemia Based on DCE-MRI

BackgroundWe evaluated skeletal muscle vascular permeability in diabetic rabbits with critical limb ischaemia using quantitative dynamic contrast agent-enhanced (DCE) magnetic resonance imaging (MRI) and explored the feasibility of using DCE-MRI Ktrans-based texture analysis for assessing early slight ischaemia-related skeletal muscle structural changes.MethodTwenty-four male New Zealand white rabbits (2.7 ± 0.3 kg; n = 12 each in sham-operated and experimental groups) underwent axial MRI of the vastus lateralis muscle at 1, 2, and 3 weeks after alloxan injection. Between-group and intra-group postoperative permeability and texture parameters were compared. Texture features of experimental groups in the third week were modelled by receiver operating characteristic (ROC) curve analysis. Correlations of permeability and of statistical texture parameters with peripheral blood endothelial progenitor cells (EPCs) and microvascular density (MVD) were analysed.ResultsIn the experimental group, the transfer constant (Ktrans) was statistically significant at all time-points (F = 5.800, P = 0.009). Their vastus lateralis muscle Ktrans was significantly lower in the third than in the first week (P = 0.018) and correlated positively with peripheral blood EPCs in the experimental group [r = 0.598, (95% CI: 0.256, 0.807)]. The rate constant was negatively associated with vastus lateralis muscle MVD [r = -0.410, (95% CI: -0.698, -0.008)]. The area under the ROC curve of texture parameters based on Ktrans in ischaemic limbs was 0.882.ConclusionsQuantitative DCE-MRI parameters could evaluate microvascular permeability of ischaemic limb skeletal muscle, and texture analysis based on DCE-MRI Ktrans allowed evaluation of early slight skeletal muscle structural changes.

In Vitro and In Vivo Degradation, Mechanical Properties, and Histocompatibility of Weft-Knitted Silk Mesh-Like Grafts

To investigate the degradation, mechanical properties, and histocompatibility of weft-knitted silk mesh-like grafts, we carried out the In Vitro and In Vivo silk grafts degradation assay. The In Vitro degradation experiment was performed by immersing the silk grafts in simulated body fluid for 1 year, and the results showed that the degradation rate of the silk mesh-like grafts was very slow, and there were few changes in the mechanical properties and quality of the silk mesh-like graft. In Vivo degradation assay was taken by implantation of the silk mesh-like grafts into the subcutaneous muscles of rabbits. At 3, 6, and 12 months postoperation, the rate of mass loss was 19.36%, 31.84%, and 58.77%, respectively, and the maximum load was 63.85%, 34.63%, and 10.76%, respectively of that prior to degradation. The results showed that the degradation rate of the silk graft and the loss of mechanical properties In Vivo were faster than the results obtained in the In Vitro experiments. In addition, there were no significant differences in secretion of serum IL-6 and TNF-α between the experimental and normal rabbits (P &gt;0.05), suggesting no obvious inflammatory reaction. The findings suggest that the weft-knitted silk mesh-like grafts have good mechanical properties, histocompatibility, and In Vivo degradation rate, and therefore represent a candidate material for artificial ligament

Definition of the mechanokinetic parameters accounting for the functional diversity of slow and fast isoforms of skeletal muscle myosin with a synthetic nanomachine

The mechanokinetic parameters characterising the force and power produced by fast (psoas) and slow (soleus) skeletal rabbit muscle are defined by feeding to a model simulation the mechanical output of a synthetic nanomachine (Pertici et al., Nat Commun 9:3532, 2018) powered by 8 heavy-mero-myosin fragments (HMM) of myosin II purified from either muscle. Implementation of a length clamp control for the minimization of the trap compliance allows to integrate the measurements of all the relevant steady state parameters (the isometric force (F0), the force-velocity relation and the maximum power (Pmax)) with transient kinetics parameters (rate of isometric force development (r) and force fluctuation due to individual motor attachment-detachment).

The K+-Dependent and -Independent Pyruvate Kinases Acquire the Active Conformation by Different Mechanisms.

Eukarya pyruvate kinases possess glutamate at position 117 (numbering of rabbit muscle enzyme), whereas bacteria have either glutamate or lysine. Those with E117 are K+-dependent, whereas those with K117 are K+-independent. In a phylogenetic tree, 80% of the sequences with E117 are occupied by T113/K114/T120 and 77% of those with K117 possess L113/Q114/(L,I,V)120. This work aims to understand these residues’ contribution to the K+-independent pyruvate kinases using the K+-dependent rabbit muscle enzyme. Residues 117 and 120 are crucial in the differences between the K+-dependent and -independent mutants. K+-independent activity increased with L113 and Q114 to K117, but L120 induced structural differences that inactivated the enzyme. T120 appears to be key in folding the protein and closure of the lid of the active site to acquire its active conformation in the K+-dependent enzymes. E117K mutant was K+-independent and the enzyme acquired the active conformation by a different mechanism. In the K+-independent apoenzyme of Mycobacterium tuberculosis, K72 (K117) flips out of the active site; in the holoenzyme, K72 faces toward the active site bridging the substrates through water molecules. The results provide evidence that two different mechanisms have evolved for the catalysis of this reaction.

Effects of vibration on the expression of mitochondrial fusion and fission genes and ultrastructure of skeletal muscle in rabbits

Objective: To study the effects of vibration on the expression of mitochondrial fusion and fission genes and ultrastructure of skeletal muscle in rabbits. Methods: Thirty-two 3.5-month-old New Zealand rabbits were randomly divided into low-intensity group, medium-intensity group, high-intensity group and control group, with 8 rabbits in each group. The rabbits in the experimental group were subjected to hind limb vibration load test for 45 days. The vibration intensity of the high intensity group was 12.26 m/s(2), the medium intensity group was 6.13 m/s(2), and the low intensity group was 3.02 m/s(2) according to the effective value of weighted acceleration[a(hw (4))] for 4 hours of equal energy frequency. The control group was exposed to noise only in the same experimental environment as the medium-intensity group. The noise levels of each group were measured during the vibration load experiment. After the test, the mRNA expression of mitochondrial fusion gene (Mfn1/Mfn2) and fission gene (Fis1, Drp1) by RT-PCR in the skeletal muscles were measured and the ultrastructure of the skeletal muscles were observed in high intensity group. Results: The mRNA expression of mitochondrial in the skeletal muscle tissues of control group, low intensity group, medium intensity group and high intensity group were Mfn1: 3.25±1.36, 3.85±1.90, 4.53±2.31 and 11.63±7.68; Mfn2: 0.68±0.25, 1.02±0.40, 0.94±0.33 and 1.40±0.45; Fis1: 1.05±0.62, 1.15±0.59, 1.53±1.06 and 2.46±1.51 and Drp1: 3.72±1.76, 2.91±1.63, 3.27±2.01 and 4.21±2.46, respectively. Compared with the control group, the expressions of Mfn1 mRNA, Mfn2 mRNA and Fis1 mRNA in the high-intensity group increased significantly (P<0.05) , and the expressions of Mfn2 mRNA in the medium-intensity group and the low-intensity group increased significantly (P<0.05) . Compared with the control group, the ultrastructure of skeletal muscle of high intensity group showed mitochondrial focal accumulation, cristae membrane damage, vacuole-like changes; Z-line irregularity of muscle fibers, and deficiency of sarcomere. Conclusion: Vibration must be lead to the abnormal mitochondrial morphology and structure and the disorder of energy metabolism due to the expression imbalance of mitochondrial fusion and fission genes in skeletal muscles of rabbits, which may be an important target of vibration-induced skeletal muscle injury.

A case for glycerol as an acceptable additive for single-particle cryoEM samples.

Buffer-composition and sample-preparation guidelines for cryo-electron microscopy are geared towards maximizing imaging contrast and reducing electron-beam-induced motion. These pursuits often involve the minimization or the complete removal of additives that are commonly used to facilitate proper protein folding and minimize aggregation. Among these admonished additives is glycerol, a widely used osmolyte that aids protein stability. In this work, it is shown that the inclusion of glycerol does not preclude high-resolution structure determination by cryoEM, as demonstrated by an ∼2.3 Å resolution reconstruction of mouse apoferritin (∼500 kDa) and an ∼3.3 Å resolution reconstruction of rabbit muscle aldolase (∼160 kDa) in the presence of 20%(v/v) glycerol. While it was found that generating thin ice that is amenable to high-resolution imaging requires long blot times, the addition of glycerol did not result in increased beam-induced motion or an inability to pick particles. Overall, these findings indicate that glycerol should not be discounted as a cryoEM sample-buffer additive, particularly for large, fragile complexes that are prone to disassembly or aggregation upon its removal.

Dietary supplementation of Allium cepa skin alters intramuscular fat, muscle cholesterol, and fatty acids in rabbits.

The high polyunsaturated fatty acids content of rabbit meat predisposes it to oxidative deterioration, which often results in reduced product quality and shelf life. This fact highlights the need to improve the antioxidant status of rabbit meat. This study investigated the effects of dietary supplementation of Allium cepa skin (ACS) on growth, carcass, intramuscular fat, muscle fatty acids, cholesterol content, meat quality, antioxidant status, and sensory attributes of hind leg muscle of rabbits. Sixty-three, 28-day-old, male New Zealand rabbits (654 ± 25 g) were randomly allocated into 21 pens of three rabbits. The pens were randomly assigned to one of three dietary treatments - ACS-0: basal diet (BD) only; ACS-25: BD + 25 g kg-1 ACS; and ACS-50: BD + 50 g kg-1 ACS - for 56 days and then euthanized. Dietary ACS did not affect growth performance and retail cuts of rabbits. Muscle cholesterol was lower (P < 0.05) in ACS-supplemented rabbits than in controls. Dietary ACS lowered (P < 0.05) dissectible fat, intramuscular fat content, C14:0, C16:0, C18:0, C18:2n-6, and C20:4n-6 levels and enhanced (P < 0.05) C18:3n-3, C20:5n-3, C22:6n-3, and C22:5n-3 concentration. Dietary ACS increased muscle catalase activity in rabbits. Sensory qualities, malondialdehyde and carbonyl contents, and physicochemical attributes of hind leg muscle of rabbits after chill storage were not influenced by dietary ACS supplementation. Supplementation with 50 g kg-1 ACS reduced intramuscular fat and cholesterol content and improved muscle n-3 fatty acids without impairing the physicochemical and sensory properties of rabbit meat. © 2021 Society of Chemical Industry.

Molecular Profiling of DNA Methylation and Alternative Splicing of Genes in Skeletal Muscle of Obese Rabbits.

DNA methylation and the alternative splicing of precursor messenger RNAs (pre-mRNAs) are two important genetic modification mechanisms. However, both are currently uncharacterized in the muscle metabolism of rabbits. Thus, we constructed the Tianfu black rabbit obesity model (obese rabbits fed with a 10% high-fat diet and control rabbits from 35 days to 70 days) and collected the skeletal muscle samples from the two groups for Genome methylation sequencing and RNA sequencing. DNA methylation data showed that the promoter regions of 599 genes and gene body region of 2522 genes had significantly differential methylation rates between the two groups, of which 288 genes had differential methylation rates in promoter and gene body regions. Analysis of alternative splicing showed 555 genes involved in exon skipping (ES) patterns, and 15 genes existed in differential methylation regions. Network analysis showed that 20 hub genes were associated with ubiquitinated protein degradation, muscle development pathways, and skeletal muscle energy metabolism. Our findings suggest that the two types of genetic modification have potential regulatory effects on skeletal muscle development and provide a basis for further mechanistic studies in the rabbit.

Characterizing Bi-substrate Enzyme Kinetics at High Resolution by 2D-ITC.

There is growing interest in using isothermal titration calorimetry (ITC) to characterize enzyme kinetics by measuring the heat produced or absorbed by catalysis in real time. Since virtually all chemical reactions are associated with changes in enthalpy, ITC represents a robust and nearly universal experimental approach. Nevertheless, there are technical challenges that limit ITC's applicability. For instance, the full kinetic characterization of enzymes with two substrates (bi-substrate enzymes), which comprise the majority of known examples, requires a series of experiments to be performed as the concentrations of both substrates are varied. This is a time-consuming and expensive process using current ITC methods since many (>5) individual experiments must be performed independently to obtain a sufficient quantity of data. We have developed a new ITC method, which we term 2D-ITC, which maps the reaction velocity as a function of two substrate concentrations in a single, roughly 2 h long experiment. This method provides a level of detail that rivals or exceeds any existing enzyme assay, as a single experiment generates on the order of 7000 catalytic rate measurements. In a proof-of-principle application to rabbit muscle pyruvate kinase (rMPK), the method correctly identified the enzyme's random sequential mechanism and allosteric catalytic suppression by the amino acid phenylalanine (Phe). Unexpectedly, we found that while Phe reduces affinity for the substrate phosphoenolpyruvate, a known phenomenon, it also alleviates inhibition by the reaction product ATP, which had not been reported previously. Given the relative abundance of ATP in the cell, this opposing effect is expected to have a substantial impact on rMPK activity.

In vivo human gracilis whole-muscle passive stress-sarcomere strain relationship.

We measured the passive mechanical properties of intact, living human gracilis muscles (n=11 individuals, 10 male and 1 female, age: 33±12 years, mass: 89±23 kg, height: 177±8 cm). Measurements were performed in patients undergoing surgery for free-functioning myocutaneous tissue transfer of the gracilis muscle to restore elbow flexion after brachial plexus injury. Whole-muscle force of the gracilis tendon was measured in four joint configurations (JC1-JC4) with a buckle force transducer placed at the distal tendon. Sarcomere length was also measured by biopsy from the proximal gracilis muscle. After the muscle was removed, a three-dimensional volumetric reconstruction of the muscle was created via photogrammetry. Muscle length from JC1 to JC4 increased by 3.3±1.0, 7.7±1.2, 10.5±1.3 and 13.4±1.2 cm, respectively, corresponding to 15%, 34%, 46% and 59% muscle fiber strain, respectively. Muscle volume and an average optimal fiber length of 23.1±0.7 cm yielded an average muscle physiological cross-sectional area of 6.8±0.7cm2 which is approximately 3 times that measured previously from cadaveric specimens. Absolute passive tension increased from 0.90±0.21N in JC1 to 16.50±2.64N in JC4. As expected, sarcomere length also increased from 3.24±0.08 µm at JC1 to 3.63±0.07 µm at JC4, which are on the descending limb of the human sarcomere length-tension curve. Peak passive muscle stress was 27.8±5.5 kPa in JC4 and muscle modulus ranged from 44.8 MPa in JC1 to 125.7 MPa in JC4. Comparison with other mammalian species indicates that human muscle passive mechanical properties are more similar to rodent muscle than to rabbit muscle. These data provide direct measurements of whole-human muscle passive mechanical properties that can be used in modeling studies and for understanding comparative passive mechanical properties among mammalian muscles.

Alkylation of rabbit muscle creatine kinase surface methionine residues inhibits enzyme activity in vitro

Creatine kinase (CK) catalyzes the formation of phosphocreatine from adenosine triphosphate (ATP) and creatine. The highly reactive free cysteine residue in the active site of the enzyme (Cys283) is considered essential for the enzymatic activity. In previous studies we demonstrated that Cys283 is targeted by the alkylating chemical warfare agent sulfur mustard (SM) yielding a thioether with a hydroxyethylthioethyl (HETE)-moiety. In the present study, the effect of SM on rabbit muscle CK (rmCK) activity was investigated with special focus on the alkylation of Cys283 and of reactive methionine (Met) residues. For investigation of SM-alkylated amino acids in rmCK, micro liquid chromatography-electrospray ionization high-resolution tandem-mass spectrometry measurements were performed using the Orbitrap technology. The treatment of rmCK with SM resulted in a decrease of enzyme activity. However, this decrease did only weakly correlate to the modification of Cys283 but was conclusive for the formation of Met70-HETE and Met179-HETE. In contrast, the activity of mutants of rmCK produced by side-directed mutagenesis that contained substitutions of the respective Met residues (Met70Ala, Met179Leu, and Met70Ala/Met179Leu) was highly resistant against SM. Our results point to a critical role of the surface exposed Met70 and Met179 residues for CK activity.

Effects of fermented rapeseed meal on gastrointestinal morphometry and meat quality of rabbits (Oryctolagus cuniculus)

The aim of the study was to determine effects of three levels of rapeseed meal (4% - FR4, 8% - FR8, and 12% - FR12) which has undergone fermentation and drying processes (FRSM) in the diet of crossbred rabbits (New Zealand White × Popielno White, n=40) on their gastrointestinal tract morphometry, internal organs weight, and proximate composition and physicochemical properties of skeletal muscles (biceps femoris – BF, and joined longissimus thoracis and longissimus lumborum – LTL). Although the total length of the digestive tract of rabbits did not differ significantly, the addition of FRSM was found to significantly (P < 0.01) affect the lengthening of caecum (between 0.73 and 0.91 m) and large intestine (from 1.07 to 1.24 m) in comparison to the control group (0.31 m and 0.54 m, respectively). Additionally, the diet with FRSM significantly (P < 0.05) influenced the weight of the heart, whereby the lightest hearts was found in the control group (10.0 g) and the heaviest in group FR8 (14.03 g).The content of proximate chemical constituents in rabbit muscle tissues was similar, with except of collagen percentage. A larger share of FRSM (from 4% to 12%) was accompanied by an increased level of collagen in LTL (P < 0.01), from 0.33% in group C to 0.46% in group FR12. In BF muscle the significantly (P < 0.01) highest collagen content was found in FR4 (2.27%) and the lowest in FR12 (0.88%). The significant decrease in the ultimate pH of LTL (from 5.71 to 5.62) and water-holding capacity (from 44.5 to 49.2 mg) as the share of FRSM in the diet increased were observed in comparison with the group C (5.74 and 37.9 mg, respectively). These effects were not noted in the BF muscle of the rabbits. A diet with FRSM significantly affected all colour parameters (CIE L*, a*, b*, C*, and h°) of the LTL and the yellowness (b*) and saturation (C*) of the BF muscle. The lightness (L*) of LTL muscles was significantly (P < 0.05) higher in the experimental rabbits, irrespective of the level of FRSM (51.50 ≤ L* ≤ 52.61), than in the control group (L*=47.51). The increased content of collagen (between 4.9 and 5.4 mg/g) and shear force (between 25.4 and 37.7 N) for cooked LTL compared to control group (4.0 mg/g and 21. N, respectively) were observed. It can be concluded that FRSM is the alternative dietary component for rabbits with no negative effect on meat full potential for further processing and case-ready purposes.

A new strategy to prepare n-HA/CS composite scaffolds with surface loading of CS microspheres

A nano-hydroxyapatite/chitosan (n-HA/CS) scaffold loading with CS microspheres was developed in this study. First, CS microspheres with an average diameter of ∼57 μm were prepared by cross-linking, and a three-dimensional (3D) printing technology was used to fabricate n-HA/CS porous scaffolds with an average pore size and porosity of 454 ± 51 μm and 60.71%, respectively. Then, the n-HA/CS scaffolds were immersed in a solution of CS microspheres and cross-linked by vanillin. The structure, porosity, composition, and cellular behavior of the CS-microsphere-loaded scaffolds were investigated. In vitro cell experiments showed that the CS microspheres on the scaffolds could effectively promote the adhesion and growth of cells on the scaffolds, suggesting that the CS microspheres and the scaffolds have good cytocompatibility. The composite scaffolds were implanted in the back muscles of rabbits for 3, 6, and 9 weeks, and the results of subsequent SEM and H&E staining analyses demonstrated that both the n-HA/CS scaffolds and the loaded CS microspheres had good biocompatibility and gradually degraded over time, where the microspheres were gradually released from the scaffolds. The strategy developed in this study for loading microspheres on scaffolds has promising prospects for future clinical applications of enhancing bone defect repair or implant integration.

Mechanochemical Synthesis and Reactivity of 1,2,3-Triazole Carbohydrate Derivatives as Glycogen Phosphorylase Inhibitors.

We have developed this work to recommend an original route for the preparation of triazole derivatives. Carbohydrates containing 1,2,3-triazole derivatives have various biological activities. Due to their advantageous and biological property, they are eye-catching synthetic targets in the arsenal of organic chemistry. Thus, finding green and efficient methods, as well as using the ball milling procedure for the synthesis of these heterocycles, is of interest to organic chemistry researchers. The objective of this study was to synthesize carbohydrate-derived triazoles under high-speed vibration milling conditions and investigate their properties. A mixture of glycoside azide derivatives (1 mmol) and prop-2-yn-1-ol (1.5 mmol) in the presence of copper (I) was vigorously shaken under vibration milling conditions at 650 rpm with three balls for 15 min. The deprotection of the resulting triazole derivatives was affected by treatment with 4M hydrochloric acid in methanol under reflux. A short and convenient route to synthesize carbohydrate-derived triazoles, based on a ball-mill via 1,3-dipolar cycloaddition reactions to prop-2-yn-1-ol, was developed. Cleavage of the isopropylidene protecting group provided water-soluble triazoles, evaluated as glycogen phosphorylase inhibitors. 1-[6- (4-Hydroxymethyl-[1,2,3]triazol-1-yl)-2,2-dimethyl-tetrahydro-furo[3,4-d][1,3]dioxol-4-yl]-ethane-1,2-diol was the best inhibitor of rabbit muscle glycogen phosphorylase b (IC50 = 60 μM). In summary, we developed new, short and convenient routes to glucose-derived 1,2,3-triazole based on 1,3-dipolar cycloaddition reactions flowed by ball milling. The use of isopropylidene protective groups gave access to the analogous deprotected water-soluble motifs, analogous to known inhibitors of glycogen phosphorylase.

Botox Injections in Paraspinal Muscles Result in Low Maximal Specific Force and Shortening Velocity in Fast but Not Slow Skinned Muscle Fibers.

Basic science, experimental animal study. To determine the effects of Botulinum toxin type A (BTX-A) injections on the mechanical properties of skinned muscle fibers (cells) of rabbit paraspinal muscles. BTX-A has been widely used in the treatment of disorders of muscle hyperactivity, such as spasticity, dystonia, and back pain. However, BTX-A injection has been shown to cause muscle atrophy, fat infiltration, and decreased force output in target muscles, but its potential effects on the contractile machinery and force production on the cellular level remain unknown. Nineteen-month-old, male New Zealand White Rabbits received either saline or BTX-A injections into the paraspinal muscles, equally distributed along the left and right sides of the spine at T12, L1, and L2 at 0, 8, 12, 16, 20, and 24 weeks. Magnetic resonance imaging was used to quantify muscle crosssectional area and structural changes before and at 28 weeks following the initial injection. Skinned fibers isolated from the paraspinal muscles were tested for their active and passive force-length relationships, unloaded shortening velocity, and myosin heavy chain isoforms. BTX-A injections led to significant fat infiltration within the injected muscles and a greater proportion of IIa to IIx fibers. Isolated fast fibers from BTX-A injected animals had lower active force and unloaded shortening velocity compared with fibers from saline-injected control animals. Force and velocity properties were not different between groups for the slow fibers. Injection of BTX-A into the paraspinal rabbit muscles leads to significant alterations in the contractile properties of fast, but not slow, fibers.Level of Evidence: N/A.

Morphological changes and functional circRNAs screening of rabbit skeletal muscle development

BackgroundThe temporal expression pattern of circular RNAs (circRNAs) across developmental stages is essential for skeletal muscle growth and functional analysis. However, there are few analyses on the potential functions of circRNAs in rabbit skeletal muscle development.ResultsInitially, the paraffin sections showed extremely significant differences in the diameter, number, area and density of skeletal muscle fibers of the fetus, child, adult rabbit hind legs (P < 0.01). Then, RNA-seq libraries of these three stages were constructed. A total of 481 differentially expressed circRNAs (DE-circRNAs) and 5,658 differentially expressed genes (DEGs) were identified. Subsequently, DE-circRNAs, whose host genes were DEGs or non-DEGs, were analyzed by GO respectively. In the fetus vs. child group, up-regulated DE-circRNAs (whose host genes were DEGs) were related to muscle fiber structure, and down-regulated ones were related to mitosis. The up-regulated DE-circRNAs (whose host genes were non-DEGs) were involved in enzyme activity, methylation and glycosylation, and the down-regulated ones were involved in mitosis and catabolism. In the fetus vs. adult group, the up-regulated DE-circRNAs (whose host genes were DEGs) were related to skeletal muscle basic structure, and the down-regulated ones were also associated with cell proliferation. But the up-regulated DE-circRNAs (whose host genes were non-DEGs) were connected with regulation of histone ubiquitination, chromatin and organelles. The down-regulated DE-circRNAs were connected with the catabolism processes. In addition, novel_circ_0022663 and novel_circ_0005489, which might have coding potential, and novel_circ_0004210 and novel_circ_0001669, which might have miRNA sponge capability, were screened out.ConclusionsIn this study, hind leg muscles of fetus, child and adult rabbits were collected for paraffin section and RNA-seq to observe the structural changes of skeletal muscle and obtain circRNA expression profiles at different stages. These data provided a catalog of circRNAs related to muscle development in New Zealand rabbits, allowing us to better understand the functional transitions in mammalian muscle development.

Diet supplemented with lycopene and selenized yeast change contents of fatty acids in the liver and femoral muscles of rabbits

The aim of our investigation was to study the impact of lycopene (Lyco) and selenized yeast (Se-Y) supplemented to the diet containing fish oil (F-O) on the profile of fatty acids (FA) in the liver and musculus biceps femoris (MBF) of rabbits. Rabbits were divided into 4 groups of 10 individuals and were fed ad libitum with the control and experimental diets for 55 days. The control diet was the basal diet (B-D) with F-O, whereas three experimental diets were the Lyco diet (the B-D with F-O and Lyco), the Se diet (the B-D with F-O and Se-Y) and the Se-Lyco diet (the B-D with F-O, Lyco and Se-Y). The Se-Lyco diet increased the content sums of all assayed FA (∑FA), saturated FA (SFA), atherogenic SFA and thrombogenic SFA in the liver and MBF compared to the control, Lyco and Se diets. Contents of cis9C16:1 (c9C16:1), c9C18:1 and c12C18:1, content sums of monounsaturated FA (∑MUFA) and odd-chain MUFA (∑Odd-MUFA), Δ9-desaturas indices and content ratios of ∑MUFA to ∑FA, and ∑Odd-MUFA to ∑FA in the liver of rabbits fed all experimental diets were lower than that of the control diet. Contents of trans10cis12C18:2, c9c12C18:2, c9c12c15C18:3, c11c14C20:2, c8c11c14C20:3, c5c8c11c14C20:4, c5c8c11c14c17C20:5, c7c10c13c16c19C22:5, c4c7c10c13c16c19C22:6 and content sums of n-6 polyunsaturated FA (n-6PUFA), n-3PUFA, PUFA, long-chain n-6PUFA (n-6LPUFA), n-3LPUFA and LPUFA in the liver of rabbits fed the diet containing Lyco without or with of Se-Y compared to the control diet. Feed supplementation with Lyco and Se-Y significantly stimulated the accumulation of n-3LPUFA in the MBF and liver and decreased ratios of the content sum of n-6PUFA to n-3PUFA and n-6LPUFA to n-3LPUFA in the MBF of rabbits. Lyco and Se-Y should be added to diets with F-O to improve the nutritive value of rabbits’ meat as it relates to human health.

Partial Decellularization for Segmental Tracheal Scaffold Tissue Engineering: A Preliminary Study in Rabbits.

In this study, we developed a new procedure for the rapid partial decellularization of the harvested trachea. Partial decellularization was performed using a combination of detergent and sonication to completely remove the epithelial layers outside of the cartilage ring. The post-decellularized tracheal segments were assessed with vital staining, which showed that the core cartilage cells remarkably remained intact while the cells outside of the cartilage were no longer viable. The ability of the decellularized tracheal segments to evade immune rejection was evaluated through heterotopic implantation of the segments into the chest muscle of rabbits without any immunosuppressive therapy, which demonstrated no evidence of severe rejection or tissue necrosis under H&E staining, as well as the mechanical stability under stress-pressure testing. Finally, orthotopic transplantation of partially decellularized trachea with no immunosuppression treatment resulted in 2 months of survival in two rabbits and one long-term survival (2 years) in one rabbit. Through evaluations of posttransplantation histology and endoscopy, we confirmed that our partial decellularization method could be a potential method of producing low-immunogenic cartilage scaffolds with viable, functional core cartilage cells that can achieve long-term survival after in vivo transplantation.