Efficient musculoskeletal annotation using free-form deformation.

Traditionally, constructing training datasets for automatic muscle segmentation from medical images involved skilled operators, leading to high labor costs and limited scalability. To address this issue, we developed a tool that enables efficient annotation by non-experts and assessed its effectiveness for training an automatic segmentation network. Our system allows users to deform a template three-dimensional (3D) anatomical model to fit a target magnetic-resonance image using free-form deformation with independent control points for axial, sagittal, and coronal directions.

Regulation of myocardial contraction as revealed by intracellular Ca measurements using aequorin.

Of the ions involved in myocardial function, Ca is the most important. Ca is crucial to the process that allows myocardium to repeatedly contract and relax in a well-organized fashion; it is the process called excitation-contraction coupling. In order, therefore, for accurate comprehension of the physiology of the heart, it is fundamentally important to understand the detailed mechanism by which the intracellular Ca concentration is regulated to elicit excitation-contraction coupling.

Myosin and tropomyosin-troponin complementarily regulate thermal activation of muscles.

Contraction of striated muscles is initiated by an increase in cytosolic Ca2+ concentration, which is regulated by tropomyosin and troponin acting on actin filaments at the sarcomere level. Namely, Ca2+-binding to troponin C shifts the "on-off" equilibrium of the thin filament state toward the "on" state, promoting actomyosin interaction; likewise, an increase in temperature to within the body temperature range shifts the equilibrium to the on state, even in the absence of Ca2+. Here, we investigated the temperature dependence of sarcomere shortening along isolated fast skeletal myofibrils using optical heating microscopy.

Rotational-motion measurement of the sacroiliac joint using upright MRI scanning and intensity-based registration: is there a sex difference?

Purpose: The sacroiliac joint (SIJ) has attracted increasing attention as a source of low back and groin pain, but the kinematics of SIJ against standing load and its sex difference remain unclear due to the difficulty of in vivo load study. An upright magnetic resonance imaging (MRI) system can provide in vivo imaging both in the supine and standing positions. The reliability of the mobility of SIJ against the standing load was evaluated and its sex difference was examined in healthy young volunteers using an upright MRI.

Mice with R2509C-RYR1 mutation exhibit dysfunctional Ca2+ dynamics in primary skeletal myocytes.

Type 1 ryanodine receptor (RYR1) is a Ca2+ release channel in the sarcoplasmic reticulum (SR) of the skeletal muscle and plays a critical role in excitation-contraction coupling. Mutations in RYR1 cause severe muscle diseases, such as malignant hyperthermia, a disorder of Ca2+-induced Ca2+ release (CICR) through RYR1 from the SR. We recently reported that volatile anesthetics induce malignant hyperthermia (MH)-like episodes through enhanced CICR in heterozygous R2509C-RYR1 mice.

Effects of omecamtiv mecarbil on the contractile properties of skinned porcine left atrial and ventricular muscles.

Omecamtiv mecarbil (OM) is a novel inotropic agent for heart failure with systolic dysfunction. OM prolongs the actomyosin attachment duration, which enhances thin filament cooperative activation and accordingly promotes the binding of neighboring myosin to actin. In the present study, we investigated the effects of OM on the steady-state contractile properties in skinned porcine left ventricular (PLV) and atrial (PLA) muscles.

Heat-hypersensitive mutants of ryanodine receptor type 1 revealed by microscopic heating.

Thermoregulation is an important aspect of human homeostasis, and high temperatures pose serious stresses for the body. Malignant hyperthermia (MH) is a life-threatening disorder in which body temperature can rise to a lethal level. Here we employ an optically controlled local heat-pulse method to manipulate the temperature in cells with a precision of less than 1 °C and find that the mutants of ryanodine receptor type 1 (RyR1), a key Ca release channel underlying MH, are heat hypersensitive compared with the wild type (WT).

Validity of Freehand 3-D Ultrasound System in Measurement of the 3-D Surface Shape of Shoulder Muscles.

Freehand 3-D ultrasound (3DUS) system is a promising technique for accurately assessing muscle morphology. However, its accuracy has been validated mainly in terms of volume by examining lower limb muscles. This study was aimed at validating 3DUS in the measurements of 3-D surface shape and volume by comparing them with magnetic resonance imaging (MRI) measurements while ensuring the reproducibility of participant posture by focusing on the shoulder muscles.

Artificial intelligence trained with integration of multiparametric MR-US imaging data and fusion biopsy trajectory-proven pathology data for 3D prediction of prostate cancer: A proof-of-concept study.

Background: We aimed to develop an artificial intelligence (AI) algorithm that predicts the volume and location of clinically significant cancer (CSCa) using convolutional neural network (CNN) trained with integration of multiparametric MR-US image data and MRI-US fusion prostate biopsy (MRI-US PBx) trajectory-proven pathology data.

Methods: Twenty consecutive patients prospectively underwent MRI-US PBx, followed by robot-assisted radical prostatectomy (RARP). The AI algorithm was trained with the integration of MR-US image data with a MRI-US PBx trajectory-proven pathology.

Synchrony of sarcomeric movement regulates left ventricular pump function in the in vivo beating mouse heart.

Sarcomeric contraction in cardiomyocytes serves as the basis for the heart's pump functions. It has generally been considered that in cardiac muscle as well as in skeletal muscle, sarcomeres equally contribute to myofibrillar dynamics in myocytes at varying loads by producing similar levels of active and passive force. In the present study, we expressed α-actinin-AcGFP in Z-disks to analyze dynamic behaviors of sequentially connected individual sarcomeres along a myofibril in a left ventricular (LV) myocyte of the in vivo beating mouse heart.

Single-cell temperature mapping with fluorescent thermometer nanosheets.

Recent studies using intracellular thermometers have shown that the temperature inside cultured single cells varies heterogeneously on the order of 1°C. However, the reliability of intracellular thermometry has been challenged both experimentally and theoretically because it is, in principle, exceedingly difficult to exclude the effects of nonthermal factors on the thermometers. To accurately measure cellular temperatures from outside of cells, we developed novel thermometry with fluorescent thermometer nanosheets, allowing for noninvasive global temperature mapping of cultured single cells.

Thermal Activation of Thin Filaments in Striated Muscle.

In skeletal and cardiac muscles, contraction is triggered by an increase in the intracellular Ca concentration. During Ca transients, Ca-binding to troponin C shifts the "" equilibrium of the thin filament state toward the "" sate, promoting actomyosin interaction. Likewise, recent studies have revealed that the thin filament state is under the influence of temperature; , an increase in temperature increases active force production.

Real-Time In Vivo Imaging of Mouse Left Ventricle Reveals Fluctuating Movements of the Intercalated Discs.

Myocardial contraction is initiated by action potential propagation through the conduction system of the heart. It has been thought that connexin 43 in the gap junctions (GJ) within the intercalated disc (ID) provides direct electric connectivity between cardiomyocytes (electronic conduction). However, recent studies challenge this view by providing evidence that the mechanosensitive cardiac sodium channels Na1.

Microscopic heat pulses activate cardiac thin filaments.

During the excitation-contraction coupling of the heart, sarcomeres are activated via thin filament structural changes (i.e., from the "off" state to the "on" state) in response to a release of Ca from the sarcoplasmic reticulum.

Optimization of Fluorescent Labeling for Nanoimaging of Sarcomeres in the Mouse Heart.

The present study was conducted to systematically investigate the optimal viral titer as well as the volume of the adenovirus vector (ADV) that expresses -actinin-AcGFP in the Z-disks of myocytes in the left ventricle (LV) of mice. An injection of 10 L ADV at viral titers of 2 to 4 × 10 viral particles per mL (VP/mL) into the LV epicardial surface consistently expressed -actinin-AcGFP in myocytes , with the fraction of AcGFP-expressing myocytes at ~10%. Our analysis revealed that SL was ~1.

Sarcomeric Auto-Oscillations in Single Myofibrils From the Heart of Patients With Dilated Cardiomyopathy.

Background: Left ventricular wall motion is depressed in patients with dilated cardiomyopathy (DCM). However, whether or not the depressed left ventricular wall motion is caused by impairment of sarcomere dynamics remains to be fully clarified.

Methods And Results: We analyzed the mechanical properties of single sarcomere dynamics during sarcomeric auto-oscillations (calcium spontaneous oscillatory contractions [Ca-SPOC]) that occurred at partial activation under the isometric condition in myofibrils from donor hearts and from patients with severe DCM (New York Heart Association classification III-IV).

The Posterior Capsular Ligamentous Complex Contributes to Hip Joint Stability in Distraction.

Background: Laxity of soft tissues after total hip arthroplasty is considered to be a cause of accelerated wear of bearing surfaces and dislocation. The purpose of this study is to assess the contribution of the anterior and posterior capsular ligamentous complexes and the short external rotators, except the quadratus femoris, on the stability of the hip against axial traction.

Methods: The study subjects comprised 7 fresh cadavers with 12 normal hip joints.

Estimation of attachment regions of hip muscles in CT image using muscle attachment probabilistic atlas constructed from measurements in eight cadavers.

Purpose: Patient-specific musculoskeletal biomechanical simulation is useful in preoperative surgical planning and postoperative assessment in orthopedic surgery and rehabilitation medicine. A difficulty in application of the patient-specific musculoskeletal modeling comes from the fact that the muscle attachment regions are typically invisible in CT and MRI. Our purpose is to develop a method for estimating patient-specific muscle attachment regions from 3D medical images and to validate with cadaver experiments.