Histochemical and ultrastructural changes of sternomastoid muscle in aged Wistar rats

Role of GABAA receptors of the dorsomedial periaqueductal grey on blood pressure and heart rate in the anesthetized rat

The midbrain dorsomedial periaqueductal grey column (dmPAG) is involved in the regulation of cardiovascular responses. Due to the presence of Gamma-Aminobutyric acid (GABA) receptors in the dmPAG, this study aimed to investigate the role of GABAA receptors in the dmPAG on cardiovascular parameters and its possible peripheral mechanisms. The left femoral artery was cannulated, and systolic arterial pressure (SAP), mean arterial pressure (MAP) and heart rate (HR) were recorded using a Power lab system. Microinjection of saline, muscimol and bicuculline (BIC) was done using a stereotaxic device. Also, the peripheral mechanisms dependent on GABAA receptors in the dmPAG were evaluated by intravenous (i.v.) injection of hexamethonium (Hexa) and atropine (Atr) 5 min before the BIC. Results showed that BIC significantly increased ∆SAP, ∆MAP and ∆HR than the control group, but muscimol had no significant effect. Injection of Hex significantly attenuates the effect of BIC on ∆SAP and ∆MAP. Atr (i.v) significantly increased the ∆HR, and when injected before BIC microinjection, it did not affect the cardiovascular responses induced by BIC. These findings show that GABAA receptors of the dmPAG have inhibitory effects on the cardiovascular system, which are mostly mediated by the sympathetic system.

Differential histological features and myogenic protein levels in distinct muscles of d-sarcoglycan null muscular dystrophy mouse model

Skeletal muscle (SkM) comprises slow and fast-twitch fibers, which differ in molecular composition, function, and systemic energy consumption. In addition, muscular dystrophies (DM), a group of diverse hereditary diseases, present different patterns of muscle involvement, progression, and severity, suggesting that the regeneration-degeneration process may differ depending on the muscle type. Therefore, the study aimed to explore the expression of proteins involved in the repair process in different muscles at an early stage of muscular dystrophy in the δ-sarcoglycan null mice (Sgcd-null), a limb-girdle muscular dystrophy 2 F model. Hematoxylin & Eosin (H&E) Staining showed a high number of central nuclei in soleus (Sol), tibialis (Ta), gastrocnemius (Gas), and extensor digitorum longus (Edl) from four months Sgcd-null mice. However, fibrosis, determined by trichrome of Gomori modified staining, was only observed in Sgcd-null Sol. In addition, the number of Type I and II fibers variated differentially in the Sgcd-null muscles vs. wild-type muscles. Besides, the protein expression level of β-catenin, myomaker, MyoD, and myogenin also presented different expression levels in all the Sgcd-null muscles studied. In summary, our study reveals that muscles with different metabolic characteristics showed distinct expression patterns of proteins involved in the muscle regeneration process. These results could be relevant in designing therapies for genetic and acquired myopathy.

Outbreaks of Avipoxvirus Clade E in Vaccinated Broiler Breeders with Exacerbated Beak Injuries and Sex Differences in Severity

Avipoxvirus affects chickens and wild birds, and it is characterized by lesions on the nonfeathered parts of the body (the cutaneous form), or necrotic lesions in the upper respiratory tract (the diphtheritic form). In poultry farming, avian pox is usually controlled by live attenuated vaccines. However, there have been many reports of outbreaks, even in flocks of vaccinated birds. In the present study, different outbreaks of the emerging clade E avipoxvirus were detected in commercial breeder flocks of chickens vaccinated against fowlpox virus in Southeast Brazil. Clinical manifestations of these outbreaks included a marked prevalence of moderate to severe progressive lesions in the beaks of affected birds, especially in roosters with increased mortality (up to 8.48%). Also, a reduced hatchability (up to 20.77% fewer hatching eggs) was observed in these flocks. Analysis of clinical samples through light and transmission electron microscopy revealed the presence of Bollinger bodies and poxvirus particles in epithelial cells and affecting chondrocytes. PCR, sequencing, and phylogenetic analysis of major core protein (P4b) and DNA polymerase (pol) genes identified this virus as clade E avipoxvirus. We also developed qPCR assays for open reading frames (ORFs) 49, 114, and 159 to detect and quantify this emergent virus. These results show the arrival and initial spread of this pathogen in the poultry industry, which was associated with harmful outbreaks and exacerbated clinical manifestations in vaccinated commercial breeder flocks. This study also highlights the relevance of permanent vigilance and the need to improve sanitary and vaccination programs.

Ultrastructural and Molecular Development of the Myotendinous Junction Triggered by Stretching Prior to Resistance Exercise

The myotendinous junction (MTJ) is a highly specialized region of the locomotor apparatus. Here, we investigated the ultrastructural and molecular effects in the MTJ region after static stretching prior to the ladder-based resistance training. Thirty-two male, 60-day old Wistar rats were divided into four groups: Sedentary, Resistance Training, Stretching, and Stretching-Resistance Training. The gastrocnemius muscle was processed for transmission electron microscopy techniques and Western blot assay. We observed that the static stretching prior to the ladder-based resistance training increased the MTJ components, the fibroblast growth factor (FGF)-2 and FGF-6 protein expression. Also, we demonstrated the lower transforming growth factor expression and no difference in the lysyl oxidase expression after combined training. The MTJ alterations in response to combined training demonstrate adaptive mechanisms which can be used for the prescription or development of methods to reduce or prevent injuries in humans and promote the myotendinous interface benefit.

Crotalphine Attenuates Pain and Neuroinflammation Induced by Experimental Autoimmune Encephalomyelitis in Mice

Multiple sclerosis (MS) is a demyelinating disease of inflammatory and autoimmune origin, which induces sensory and progressive motor impairments, including pain. Cells of the immune system actively participate in the pathogenesis and progression of MS by inducing neuroinflammation, tissue damage, and demyelination. Crotalphine (CRO), a structural analogue to a peptide firstly identified in Crotalus durissus terrificus snake venom, induces analgesia by endogenous opioid release and type 2 cannabinoid receptor (CB2) activation. Since CB2 activation downregulates neuroinflammation and ameliorates symptoms in mice models of MS, it was presently investigated whether CRO has a beneficial effect in the experimental autoimmune encephalomyelitis (EAE). CRO was administered on the 5th day after immunization, in a single dose, or five doses starting at the peak of disease. CRO partially reverted EAE-induced mechanical hyperalgesia and decreased the severity of the clinical signs. In addition, CRO decreases the inflammatory infiltrate and glial cells activation followed by TNF-α and IL-17 downregulation in the spinal cord. Peripherally, CRO recovers the EAE-induced impairment in myelin thickness in the sciatic nerve. Therefore, CRO interferes with central and peripheral neuroinflammation, opening perspectives to MS control.

Macro- and microstructures of the digestive tract in the Eurasian collared dove, Streptopelia decaocto (Frivaldszky 1838): Adaptive interplay between structure and dietary niche

We describe the functional morphology of the digestive tract of the Eurasian collared dove, Streptopelia decaocto using anatomical, morphometric, histological, histochemical, and ultrastructure techniques, and relate our findings to the species' dietary niche. Our results revealed that the esophagus is displaced on both sides of the neck and has highly folded tunica mucosa, which confer greater elasticity for efficient swallowing and passage of food to the crop. The proventriculus is delicate and its mucosal layer contains polymorphic glands with dense profound and superficial secretory units that open to the luminal surface by gastric pores. The ventriculus is biconvex and lined with a keratinized koilin membrane. The tubular glands within the mucosal lining include the isthmus, the neck, and the basal segment that comprise chief and basal cells with prominent nuclei. At the cuticle-mucosal interface, pyramidal vertical rodlets of the cuticle are secreted and superficially covered by a thin film of a horizontal matrix. The mucosa of the ileum form pyramidal villi that are oriented perpendicularly to the central lumen. Enterocytes infiltrated with goblet cells make up the epithelial lining of the villi. There are subtle differences in the thicknesses of corresponding tunics together with histochemical reactions of alcian blue (AB) and Masson-Goldner trichrome (MT) for their microstructures. Overall, our findings reveal remarkable convergence of both macro-and microstructures in S. decaocto to other granivorous species, and offer further evidence of the close association between functional morphology and feeding style relative to food swallowing, digestion, and absorption.

Effects of physical training on sarcomere lengths and muscle-tendon interface of the cervical region in an experimental model of menopause

The aim of this study was to describe the structural and ultrastructural aspects of the myotendinous junction (MTJ) and the proximal and distal sarcomeres of the sternomastoid of aged Wistar rats subjected to an experimental model of menopause and swimming training. A total of 20 female elderly rats were divided into the following four groups (n=5 in each group): sedentary/no-menopausal (SNM), trained/no-menopausal (TNM), sedentary/menopausal (SM), and trained/menopausal (TM). The MTJ samples were dissected and analyzed using transmission electron microscopy. We showed that the TNM Group rats exhibited changes in morphological characteristics as a consequence of physical exercise, which included an increase of 36.60% (P<0.001) in the evagination length of the MTJ and a reduction in the length of the distal (77.38%) (P<0.0001) and proximal (68.15%) (P<0.0001) sarcomeres. The SM Group exhibited a reduction of about 275.93% (P<0.001) in the muscle-tendon interface and in the lengths of distal sarcomeres (55.87%) (P<0.0001) compared with SNM Group. Our results suggest that the swimming training under experimental model of menopause promoted tissue reorganization and increased muscle-tendon interaction with a drastic development in the length and thickness of the sarcoplasmatic invaginations and evaginations. In addition, the sarcomeres exhibited different lengths and a reduction in both groups subjected to swimming training.

Muscle spindles of the rat sternomastoid muscle

The sternomastoid (SM) muscle in rodents presents a peculiar distribution of fiber types with a steep gradient from the ventral, superficial, white portion to the dorsal, deep, red region, where muscle spindles are restricted. Cross section of the medial longitudinal third of the rat SM contains around 10,000 muscle fibers with a mean diameter of 51.28±12.62 (μm +/- SD). Transverse sections stained by Succinate Dehydrogenase (SDH) reaction clearly presents two distinct regions: the dorsal deep red portion encompassing a 40% cross section area contains a high percentage of packed SDH-positive muscle fibers, and the ventral superficial region which contains mainly SDH-negative muscle fibers. Indeed, the ventral superficial region of the rat SM muscle contains mainly fast 2B muscle fibers. These acidic ATPase pH 4.3-negative and SDH-negative 2B muscle fibers are the largest of the SM muscle, while the acidic ATPase pH 4.3-positive and SDH-positive Type 1 muscle fibers are the smallest. Here we show that in thin transverse cryosections only 2 or 3 muscle spindle are observed in the central part of the dorsal deep red portion of the SM muscle. Azan Mallory stained sections allow at the same time to count the spindles and to evaluate aging fibrosis of the skeletal muscle tissue. Though restricted in the muscle red region, SM spindles are embedded in perimysium, whose changes may influence their reflex activity. Our findings confirm that any comparisons of changes in number and percentage of muscle spindles and muscle fibers of the rat SM muscle will require morphometry of the whole muscle cross-section. Muscle biopsies of SM muscle from large mammals will only provide partial data on the size of the different types of muscle fibers biased by sampling. Nonetheless, histology of muscle tissue continue to provide practical and low-cost quantitative data to follow-up translational studies in rodents and beyond.

Myotendinous junction plasticity in aged ovariectomized rats submitted to aquatic training

The study aims to describe the tissue plasticity of MTJ through the morphological analysis of MTJ soleus in ovariectomized aged female Wistar rats submitted to aquatic training. Forty aged Wistar rats, 1 year and 2 months of age, were divided into four groups: sedentary (S), trained (T), ovariectomized (O), and trained/ovariectomized (OT). Employing the transmission electron microscopy, the ultrastructural and morphometric elements were revealed. In the S group, changes in morphological characteristics as a consequence of the aging process were seen, demonstrated by the conical shape of the muscle cell extremity, a large area with collagen deposit, and misalignment of sarcomeres in series. The T group presented ample adjustments when revealed the organization of MTJ, through the increase of the contact area and greater lengths of sarcoplasmatic invaginations and evaginations. The O group revealed extensive tissue disorganization with muscle atrophy, reduction of MTJ contact area, and consequently, changes in sarcoplasmatic invaginations and evaginations. The OT group demonstrated extensive remodeling with restructuring MTJ through the increase of tissue contact area, extensive organization, parallel arrangement, and increased length of sarcoplasmatic invaginations and evaginations. The distal sarcomeres presented higher lengths compared to the proximal sarcomeres in both the groups. We conclude that aquatic training was effective in the organization and structural remodeling of the myotendinous interface of ovariectomized aged rats. There was a greater area of contact, and consequently, greater resistance in the myotendinous interface promoting a lower predisposition to injuries.

Revisiting the peculiar regional distribution of muscle fiber types in rat Sternomastoid Muscle

The sternomastoid (SM) muscle in rodents is known to have a peculiar distribution of fiber types with a steep gradient from surface to deep region. We here further characterize this peculiar regional distribution by quantitative histochemical morphometrys. In Hematoxylin-Eosin (H-E) stained transverse cryosections harvested in the medial portion of the muscle we counted around 10.000 myofibers with a mean diameter of 51.3±12.6 (μm). Cryisections of the SM stained by SDH reaction clearly show two distinct regions, toward the deep surface of the muscle a 40% area that contains packed SDH-positive myofibers, while the remaining area of the SM toward the external surface presents a more checker-board appearance. On the other hand, in the deep region of SM type 1 (slow contracting) muscle fibers, caracterized by positive acidic ATPase pH 4.35 reaction, are only the 24.5% of the fibers in the deep area of SM muscles, being restricted to the deepest region. The 75.5% of the myofibers in the deep region are of the fast contracting types (either 48.4% 2A, SDH -positive fibers or 27.1% 2B, SDH-negative fibers, respectively). As expected the 2B muscle fibers, acidic ATPase pH 4.3-negative and SDH-negative, present the largest size, while Type 1 fibers, acidic ATPase pH 4.3-positive and SDH-positive, present the smallest size in rat SM muscle. Based on present and previous observations, comparison of change in absolute number and/or percentage of the fiber types in any experimental model of muscle atrophy/hypertrophy/plasticity/pathology /recovery in the rat SM, and possibly of all mammals, will ask for morphometry of the whole muscle cross-sections, muscle sampling by bioptic approches will provide only comparable data on the size of the different types of muscle fibers.

Exciting perspectives for Translational Myology in the Abstracts of the 2018Spring PaduaMuscleDays: Giovanni Salviati Memorial - Chapter IV - Abstracts of March 17, 2018

Myologists working in Padua (Italy) were able to continue a half-century tradition of studies of skeletal muscles, that started with a research on fever, specifically if and how skeletal muscle contribute to it by burning bacterial toxin. Beside main publications in high-impact-factor journals by Padua myologists, I hope to convince readers (and myself) of the relevance of the editing Basic and Applied Myology (BAM), retitled from 2010 European Journal of Translational Myology (EJTM), of the institution of the Interdepartmental Research Center of Myology of the University of Padova (CIR-Myo), and of a long series of International Conferences organized in Euganei Hills and Padova, that is, the PaduaMuscleDays. The 2018Spring PaduaMuscleDays (2018SpPMD), were held in Euganei Hills and Padua (Italy), in March 14-17, and were dedicated to Giovanni Salviati. The main event of the “Giovanni Salviati Memorial”, was held in the Aula Guariento, Accademia Galileiana di Scienze, Lettere ed Arti of Padua to honor a beloved friend and excellent scientist 20 years after his premature passing. Using the words of Prof. Nicola Rizzuto, we all share his believe that Giovanni “will be remembered not only for his talent and originality as a biochemist, but also for his unassuming and humanistic personality, a rare quality in highly successful people like Giovanni. The best way to remember such a person is to gather pupils and colleagues, who shared with him the same scientific interests and ask them to discuss recent advances in their own fields, just as Giovanni have liked to do”. Since Giovanni’s friends sent many abstracts still influenced by their previous collaboration with him, all the Sessions of the 2018SpPMD reflect both to the research aims of Giovanni Salviati and the traditional topics of the PaduaMuscleDays, that is, basics and applications of physical, molecular and cellular strategies to maintain or recover functions of skeletal muscles. The translational researches summarized in the 2018SpPMD Abstracts are at the appropriate high level to attract endorsement of Ethical Committees, the interest of International Granting Agencies and approval for publication in top quality international journals. The abstracts of the presentations of the March 16, 2018 Padua Muscle Day and those of the remaining Posters are listed in this chapter IV. The Author Index of the 2018Spring PaduaMuscleDays follows at page 78.

Muscle fiber viability, a novel method for the fast detection of ischemic muscle injury in rats

Acute lower extremity ischemia is a limb- and life-threatening clinical problem. Rapid detection of the degree of injury is crucial, however at present there are no exact diagnostic tests available to achieve this purpose. Our goal was to examine a novel technique - which has the potential to accurately assess the degree of ischemic muscle injury within a short period of time - in a clinically relevant rodent model. Male Wistar rats were exposed to 4, 6, 8 and 9 hours of bilateral lower limb ischemia induced by the occlusion of the infrarenal aorta. Additional animals underwent 8 and 9 hours of ischemia followed by 2 hours of reperfusion to examine the effects of revascularization. Muscle samples were collected from the left anterior tibial muscle for viability assessment. The degree of muscle damage (muscle fiber viability) was assessed by morphometric evaluation of NADH-tetrazolium reductase reaction on frozen sections. Right hind limbs were perfusion-fixed with paraformaldehyde and glutaraldehyde for light and electron microscopic examinations. Muscle fiber viability decreased progressively over the time of ischemia, with significant differences found between the consecutive times. High correlation was detected between the length of ischemia and the values of muscle fiber viability. After reperfusion, viability showed significant reduction in the 8-hour-ischemia and 2-hour-reperfusion group compared to the 8-hour-ischemia-only group, and decreased further after 9 hours of ischemia and 2 hours of reperfusion. Light- and electron microscopic findings correlated strongly with the values of muscle fiber viability: lesser viability values represented higher degree of ultrastructural injury while similar viability results corresponded to similar morphological injury. Muscle fiber viability was capable of accurately determining the degree of muscle injury in our rat model. Our method might therefore be useful in clinical settings in the diagnostics of acute ischemic muscle injury.

Structural and ultrastructural features of the agouti tongue (Dasyprocta aguti Linnaeus, 1766)

The agouti (Dasyprocta aguti Linnaeus, 1766) is a wild rodent belonging to the family Dasyproctidae that is found throughout Brazil and feeds on fruits and seeds. The aim of the present study was to describe the following features of the tongue of agouti: its morphological structures, the three-dimensional characteristics of the lingual papillae surface, the connective tissue cores (CTCs) and the epithelial cell ultrastructure. Four types of papillae were observed on the dorsal surface of the tongue with a triangular shape: filiform, fungiform, foliate and vallate. Filiform papillae were distributed throughout the tongue surface, and removal of the epithelial surface revealed conical CTCs and multifilaments. Fungiform papillae were observed in the rostral and middle regions, whereas foliate papillae developed in pairs on the lateral margin of the caudal region. Removal of the epithelium in these regions revealed CTCs with parallel laminar conformation. Vallate papillae were arranged in a V-shape in the caudal region, and their CTCs ranged in shape from elongate to ovoid. The ultrastructural components of the dorsal epithelium were the basal, spinous, granular and keratinised layers. A broad area with cytoplasmic projections was identified in the interface region between the lamina propria and the basal layer. Flattened cells with intermediate filaments were observed in the transitional region between spinous and granular layers. The keratinised layer was composed of superimposed epithelial cells where desmosomes and cell-surface microridges were observed. These structural features, including the three-dimensional aspects of the lingual papillae, the CTCs and the epithelial ultrastructure, indicate that when compared with other animals, particularly other rodent species, the morphological features of the tongue of agouti are relatively well developed, especially regarding foliate and vallate papillae.

Qualitative study of young, adult, and aged Wistar rats temporomandibular synovial membrane employing light, scanning, and transmission electron microscopy

The aim of this study was to analyze the rat temporomandibular joint (TMJ) synovial membrane at different ages using light, scanning, and transmission electron microscopy. Under light microscopic analysis, the TMJ structures were observed such as condyle, capsule, disk, the synovial membrane collagen type, and cells distribution. In the scanning electron microscopy, the synovial membrane surface exhibited a smooth aspect in young animals and there was an increase with ageing in the number of folds. The transmission electron microscopic analysis showed more synoviocytes in the synovial layer in the young group and still a great number of vesicles and cisterns dilation of rough endoplasmic reticulum in the aged group. In the three groups, a dense layer of collagen fibers in the synovial layer and cytoplasmic extensions were clearly seen. It was possible to conclude that synovial membrane structures in aged group showed alterations contributing to the decrease in joint lubrication and in the sliding between disk and joint surfaces. These characteristic will reflect in biomechanics of chewing, and may cause the TMJ disorders, currently observed in clinical processes.

Ultrastructural features of the myotendinous junction of the sternomastoid muscle in Wistar rats: from newborn to aging

The myotendinous junction (MTJ) is a major area for transmitting force from the skeletal muscle system and acts in joint position and stabilization. This study aimed to use transmission electron microscopy to describe the ultrastructural features of the MTJ of the sternomastoid muscle in Wistar rats from newborn to formation during adulthood and possible changes with aging. Ultrastructural features of the MTJ from the newborn group revealed pattern during development with interactions between muscle cells and extracellular matrix elements with thin folds in the sarcolemma and high cellular activity evidenced through numerous oval mitochondria groupings. The adult group had classical morphological features of the MTJ, with folds in the sarcolemma forming long projections called "finger-like processes" and sarcoplasmic invaginations. Sarcomeres were aligned in series, showing mitochondria near the Z line in groupings between collagen fiber bundles. The old group had altered "finger-like processes," thickened in both levels of sarcoplasmic invaginations and in central connections with the lateral junctions. We conclude that the MTJ undergoes intense activity from newborn to its formation during adulthood. With increasing age, changes to the MTJ were observed in the shapes of the invaginations and "finger-like processes" due to hypoactivity, potentially compromising force transmission and joint stability.

Fine structure of myotendinous junction between the anterior belly of the digastric muscle and intermediate tendon in adults rats

This study analyzed the ultrastructural characteristics of the myotendinous junction (MTJ) between anterior belly of digastrics muscle and the intermediate tendon in adult rats. Six male Wistar rats were used and were anesthetized with an overdose of urethane and sacrificed by intracardiac perfusion with modified Karnovsky solution, postfixed in 1% osmium tetroxide, dehydrated in increasing series of alcohols and embedded in Spurr resin for transmission electron microscopic analysis. Ultrastructural analysis showed conical shape of the fiber extremity in MTJ region, highlighting the presence of numerous mitochondria arranged in groups in the subsarcolemmal and intermyofibrillary regions. Atypical MTJ characteristics were seen interspersed with bundles of collagen fibers. Classic characteristics such as finger-like processes by means of sarcoplasmic projections were observed among interdigitations. Terminals and periphericals bundles of myofibrils showed close relationship with the adjacent muscle fiber's endomysium through lateral junctions. In the distal portion, it was observed that the communication region of microtendons forming the intermediate tendon of digastric muscle, and it can highlight the columns disposition of tenocytes. In conclusion, the MTJ ultrastructure between the anterior belly of digastric muscle and intermediate tendon of adult rats showed classical morphologic descriptions and presented an atypical region revealed by the subspecialization between the myofibrils bundles and collagen fibers in the MTJ region.