RESUMEN
Many biological processes are triggered or driven by mechanical forces in the cytoskeletal network, but these transducing forces have rarely been assessed. Striated muscle, with its well-organized structure provides an opportunity to assess intracellular forces using small-angle X-ray fiber diffraction. We present a new methodology using Monte Carlo simulations of muscle contraction in an explicit 3D sarcomere lattice to predict the fiber deformations and length changes along thin filaments during contraction. Comparison of predicted diffraction patterns to experimental meridional X-ray reflection profiles allows assessment of the stepwise changes in intermonomer spacings and forces in the myofilaments within living muscle cells. These changes along the filament length reflect the effect of forces from randomly attached crossbridges. This approach enables correlation of the molecular events, such as the current number of attached crossbridges and the distributions of crossbridge forces to macroscopic measurements of force and length changes during muscle contraction. In addition, assessments of fluctuations in local forces in the myofilaments may reveal how variations in the filament forces acting on signaling proteins in the sarcomere M-bands and Z-discs modulate gene expression, protein synthesis and degradation, and as well to mechanisms of adaptation of muscle in response to changes in mechanical loading.
Asunto(s)
Citoesqueleto de Actina/fisiología , Actinas/fisiología , Contracción Isométrica/fisiología , Músculo Estriado/fisiología , Miosinas/fisiología , Sarcómeros/fisiología , Citoesqueleto de Actina/ultraestructura , Actinas/ultraestructura , Animales , Simulación por Computador , Conectina/fisiología , Conectina/ultraestructura , Modelos Biológicos , Método de Montecarlo , Músculo Estriado/diagnóstico por imagen , Miosinas/ultraestructura , Rana catesbeiana/fisiología , Sarcómeros/ultraestructura , Dispersión del Ángulo Pequeño , Técnicas de Cultivo de Tejidos , Difracción de Rayos XRESUMEN
BACKGROUND: Delayed bleeding is the most common significant complication after piecemeal endoscopic mucosal resection (p-EMR) of large nonpedunculated colorectal polyps (NPCPs). Risk factors for delayed bleeding are incompletely defined. We aimed to determine risk factors for delayed bleeding following p-EMR. METHODS: Data were analyzed from a prospective tertiary center audit of patients with NPCPsâ≥â20âmm who underwent p-EMR between 2010 and 2012.âPatient, polyp, and procedure-related data were collected. Four post p-EMR defect factors were evaluated for interobserver agreement and included in analysis. Delayed bleeding severity was reported in accordance with guidelines. Predictors of bleeding were identified. RESULTS: Delayed bleeding requiring hospitalization occurred after 22 of 330 procedures (6.7â%). A total of 11 patients required blood transfusion; of these, 4 underwent urgent colonoscopy, 1 underwent radiological embolization, and 1 required surgery. Interobserver agreement for identification of the four post p-EMR defect factors was moderate (kappa range 0.52â-â0.57). Factors associated with delayed bleeding were visible muscle fibers (Pâ=â0.03) and the presence of a "cherry red spot" (Pâ=â0.05) in the post p-EMR defect. Factors not associated with delayed bleeding were American Association of Anesthesiologists class, aspirin use, polyp size, site, and use of argon plasma coagulation. CONCLUSIONS: Visible muscle fibers and the presence of a "cherry red spot" in the resection defect were associated with delayed bleeding after p-EMR. These findings suggest evaluation and photodocumentation of the post p-EMR defect is important and, when considered alongside other patient and procedural factors, may help to reduce the incidence and severity of delayed bleeding.
Asunto(s)
Pólipos del Colon/cirugía , Resección Endoscópica de la Mucosa/efectos adversos , Hemorragia Posoperatoria/etiología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Colon , Resección Endoscópica de la Mucosa/métodos , Femenino , Hospitalización , Humanos , Masculino , Auditoría Médica , Persona de Mediana Edad , Músculo Liso/diagnóstico por imagen , Músculo Estriado/diagnóstico por imagen , Estudios Prospectivos , Recto , Factores de Riesgo , Factores de Tiempo , Adulto JovenRESUMEN
AIMS: Investigation of the function of the striated urogenital sphincter (SUS) is challenging because it is difficult to access and requires invasive measures. Ultrasound shear wave elastography (SWE) is a non-invasive real-time technique used to estimate tissue stiffness. As muscle stiffness can be used as an estimate of muscle force, SWE provides an opportunity to study contraction of the peri-urethral musculature. Validation of SWE to study SUS during functional tasks, such as pelvic floor muscle contractions, is required prior to application in clinical populations. METHODS: Ten healthy females (34[5] years) participated. Stiffness in a region expected to contain the SUS was quantified using SWE at rest and during a pelvic floor muscle contractions performed at 10%, 25%, and 50% of maximal voluntary contraction (MVC). Two repetitions were performed for 10 s. RESULTS: During contraction, stiffness increased in the region of the SUS in all participants and at all contraction intensities. Multiple regions of increased stiffness were detected, with 95.8% of regions situated ventral to the mid-urethra within the anatomical area of the SUS. The increase in stiffness was greater for 50% MVC than both 10% and 25% MVC contraction intensities (P < 0.01). CONCLUSIONS: Stiffness increased within the anatomical region of the SUS during voluntary pelvic floor muscle contractions with predictable response to changes in contraction intensity. These observations support the potential for ultrasound SWE to study SUS function non-invasively.
Asunto(s)
Músculo Estriado/diagnóstico por imagen , Músculo Estriado/fisiología , Diafragma Pélvico/diagnóstico por imagen , Diafragma Pélvico/fisiología , Sistema Urogenital/diagnóstico por imagen , Sistema Urogenital/fisiología , Adulto , Diagnóstico por Imagen de Elasticidad , Electromiografía , Femenino , Humanos , Contracción Muscular/fisiología , Reproducibilidad de los Resultados , Ultrasonografía , Uretra/fisiologíaRESUMEN
PURPOSE: This study aimed to use the multiscale blob feature (MBF) method to quantitatively evaluate porcine striated muscle injuries. METHODS: A porcine striated muscle injury model was induced by microwave ablation and anhydrous acetic acid injection, respectively. Then, both 2D sonographic and histological features of the lesions were recorded and compared. Later, MBF was used to quantitatively evaluate the porcine striated muscle injuries by extracting the texture features from the 2D ultrasonogram via measuring eight textural parameters (Mean, SDev, NOB, [Formula: see text], [Formula: see text], HOD, DOD, and POD). RESULTS: Microwave ablation produced oval or round-like lesions, which had a pale gray color, with an echo attenuation detected at lesion center due to carbonization; anhydrous acetic acid injection produced long, stripped lesions, which had a slate-gray color, with a gas-like intense echo at lesion center. There were significant differences in Mean, [Formula: see text] and POD between the muscle samples treated by microwave ablation and the control samples, as well as significant differences in NOB, [Formula: see text] and POD between the muscle samples treated by anhydrous acetic acid injection and the control. There were significant differences in Mean, [Formula: see text], NOB, and [Formula: see text] between the muscle samples treated by microwave ablation and those treated by anhydrous acetic acid injection. CONCLUSION: Quantitative evaluation of striated muscle injuries using the MBF method was able to differentiate the muscle injuries caused by microwave ablation and anhydrous acetic acid injection, suggesting that this method may be a potential and reliable tool for quantitative evaluation of muscle injuries.
Asunto(s)
Músculo Estriado/diagnóstico por imagen , Músculo Estriado/lesiones , Ácido Acético , Animales , Modelos Animales de Enfermedad , Microondas , PorcinosRESUMEN
According to the current opinion, lymph-heart striated muscle represents a specialized type of skeletal muscles in frogs. Here, we studied muscle fibers in mechanically damaged lymph hearts during the first postoperative week using electron-microscopic autoradiography. We present evidence that both, the satellite cells and pre-existing muscle fibers bordering the site of injury, contribute directly to the lymph-heart muscle regeneration. Several muscle fibers located in the vicinity of the damaged area displayed features of nuclear and sarcoplasmic activation. We also observed ultrastructural changes indicating activation of a few satellite cells, namely decondensation of chromatin, enlargement of nuclei and nucleoli, appearance of free ribosomes and rough endoplasmic reticulum tubules in the cytoplasm. Electron-microscopic autoradiography showed that 4 h after single (3)H-thymidine administration on the seventh day after injury not only the activated satellite cells, but also some nuclei of myofibers bordering the injured zone are labeled. We showed that both, the myonuclei of fibers displaying the signs of degenerative/reparative processes in the sarcoplasm and the myonuclei of the fibers enriched with highly organized myofibrils, can re-enter into the S-phase. Our results indicate that the nuclei of lymph-heart myofibers can reactivate DNA synthesis during regenerative myogenesis, unlike the situation in regenerating frog skeletal muscle where myogenic cells do not synthesize DNA at the onset of myofibrillogenesis.
Asunto(s)
Músculo Estriado/ultraestructura , Animales , Núcleo Celular/ultraestructura , Vasos Linfáticos/citología , Desarrollo de Músculos , Músculo Estriado/diagnóstico por imagen , Músculo Estriado/fisiología , Radiografía , Rana temporaria , RegeneraciónRESUMEN
OBJECTIVE: We evaluated the postmortem changes of striated muscle by comparing computed tomography (CT) images obtained postmortem and antemortem in the same patients. MATERIALS AND METHODS: We studied 33 consecutive patients who underwent antemortem CT, postmortem CT, and pathological autopsy in our tertiary care hospital between April 2009 and December 2010. Postmortem CT was performed within 20 h after death and was followed by pathological autopsy. Pathological autopsy confirmed the absence of muscular diseases such as amyotrophic lateral sclerosis, muscular dystrophy, myositis, and myasthenia, in all of the patients. The CT attenuation values of four cardiac muscle sites (anterior wall of the left ventricle, left ventricular free wall, posterior wall of the left ventricle, and the ventricular septum) and two skeletal muscle sites (the pectoralis major muscle and the erector spinae muscle) were compared between antemortem and postmortem CT using paired t test. RESULTS: Striated muscle had significantly greater attenuation on postmortem CT than on antemortem CT (P<0.001) in all six tissue sites. No significant association was found between postmortem change in the CT attenuation of striated muscle and gender, age, or elapsed time since death. CONCLUSION: This is the first longitudinal study to show hyperattenuation of striated muscle on postmortem CT images compared with antemortem CT images in the same patients.
Asunto(s)
Músculo Estriado/diagnóstico por imagen , Músculo Estriado/patología , Tomografía Computarizada por Rayos X , Adulto , Anciano , Anciano de 80 o más Años , Autopsia , Femenino , Humanos , Masculino , Persona de Mediana Edad , Músculo Esquelético/patología , Miocardio/patología , Cambios Post Mortem , Adulto JovenRESUMEN
PET/CT is widely used in the staging and assessment of therapeutic response in patients with malignancies. Accurate interpretation of PET/CT requires knowledge of the normal physiologic distribution of [18F]-fluoro-2-deoxy-d-glucose, artifacts due to the use of CT for attenuation correction of the PET scan and potential pitfalls due to malignancies that are PET negative and benign conditions that are PET positive. Awareness of these artifacts and potential pitfalls is important in preventing misinterpretation that can alter patient management.
Asunto(s)
Imagen Multimodal , Tomografía de Emisión de Positrones , Tórax , Tomografía Computarizada por Rayos X , Tejido Adiposo Pardo/diagnóstico por imagen , Artefactos , Reacciones Falso Positivas , Humanos , Neoplasias Pulmonares/diagnóstico , Músculo Estriado/diagnóstico por imagen , Radiografía Torácica , Tórax/diagnóstico por imagenRESUMEN
We developed a modified transcranial sonography technique to study the morphology of the temporal lobe, a brain region involved in language, memory and social functions in humans that can be visualized in correspondence of the acoustic window of the temporal squama. Previous studies raise the possibility that a unique derived feature of Homo sapiens is a relatively larger temporal lobe compared to those of other hominins and apes. Such a brain reorganization might have contributed to the evolution of various "higher" cognitive functions of Homo sapiens, including language. Hence, the importance of further comparative analyses of the temporal region. With the technique that we developed we were able to study the meninges, the subarachnoidal space and the cortex of the human temporal lobe. The spatial resolution and the ability to visualize structures of 200-300 microm size led us to hypothesize that the linear structures parallel to the subarachnoidal space might be referred to the neuronal layers of the cortex. The low cost, simplicity and safety of the procedure suggest that this technique may have a significant potential in the comparative study of the primate temporal lobe. Furthermore, the procedure described here can also be used for the study of vascularization of the meninges, in order to better understand the evolutionary relationships between the neurocranial shape and the middle meningeal vessels in living and fossil human species.
Asunto(s)
Lóbulo Temporal/diagnóstico por imagen , Ultrasonografía Doppler Transcraneal/métodos , Adulto , Animales , Corteza Cerebral/diagnóstico por imagen , Femenino , Humanos , Masculino , Meninges/diagnóstico por imagen , Persona de Mediana Edad , Músculo Estriado/diagnóstico por imagen , Primates , Ultrasonografía Doppler Transcraneal/veterinariaRESUMEN
Characterization of tissue elasticity (stiffness) and viscosity has important medical applications because these properties are closely related to pathological changes. Quantitative measurement is more suitable than qualitative measurement (i.e., mapping with a relative scale) of tissue viscoelasticity for diagnosis of diffuse diseases where abnormality is not confined to a local region and there is no normal background tissue to provide contrast. Shearwave dispersion ultrasound vibrometry (SDUV) uses shear wave propagation speed measured in tissue at multiple frequencies (typically in the range of hundreds of Hertz) to solve quantitatively for both tissue elasticity and viscosity. A shear wave is stimulated within the tissue by an ultrasound push beam and monitored by a separate ultrasound detect beam. The phase difference of the shear wave between 2 locations along its propagation path is used to calculate shear wave speed within the tissue. In vitro SDUV measurements along and across bovine striated muscle fibers show results of tissue elasticity and viscosity close to literature values. An intermittent pulse sequence is developed to allow one array transducer for both push and detect function. Feasibility of this pulse sequence is demonstrated by in vivo SDUV measurements in swine liver using a dual transducer prototype simulating the operation of a single array transducer.