What Is the Role of Contractile Proteins in Muscles

The study of contractile protein expression by immunohistochemistry has the advantage that protein expression and morphological data are provided in the same experiment. However, measuring multiple contractile proteins requires multiple slides as it can be technically difficult to look for multiple antibodies on a single slide, depending on the species from which the required secondary antibodies are generated. The cells must be plated on covering glasses and fixed according to morphology (point The primary antibodies and dilutions recommended based on our experience are shown in Table 3. We use secondary antibodies conjugated with horseradish peroxidase or alkaline phosphatase for optical microscopy or fluorescent conjugates such as TRITC or Alexa Fluor 488 or 568 for confocal microscopy. Examples of immunohistochemical staining of calponin and actin SM-α in response to rapamycin-induced differentiation are shown in Figure 7 (Optical Microscopy, 7a; Confocal fluorescence microscopy, 7b). We published similar experiments with antibodies against SM-MHC, calponin and actin SM-α (Martin et al. 2004). One caveat to this approach is that the results obtained with this method are not easily quantifiable. The best way to present this data is often to display multiple panels of representative fields.

The geometric interposition of various contractile proteins (especially actin, myosin, troponin, tropomyosin and α-actinin) gives myofibrils a characteristic repetitive pattern of stripes or bands, the basic unit of which is known as sarcomeres (Fig. 1 and 4). Sarcomeres in mammalian ventricular cells have a characteristic resting length of about 2.2 μm. Their most obvious components are Z-bands (“Z-lines”, “Z-discs”), A bands and I bands; the less visible segments are the M-band-L line complex or the “pseudo-H-zone” in the middle of the sarcoma (Fig. 4 and 5). Although a sarcomere, stricto sensu, comprises two “half” I bands, an A band and the halves transversely cut in two of two Z bands (Fig. 4), the popular convention considers a sarcomere as any segment tightened by Z bands. The A bands (“anisotropics”) are areas where the actin and myosin filaments overlap, while the I bands (for “isotropics”) are areas of sarcoma in which the actin filaments stand alone. At the intermediate level of the sarcomere, where the actin filaments in the relaxed myofibrils do not extend, a pair of relatively light L-lines flanks a dark M band, the turbidity of which results from the presence of transverse bridges between myosin and myosin.

The presence of M ligaments in the heart is actually a sign of the maturity of the myocardial cell; in the heart of the rat, the M bands occur only after birth and are completely absent in the embryonic heart. An increase in the cytoplasmic concentration of Ca2+, which activates the contractile process in smooth vascular muscle cells, may be due to increased permeability of the cell membrane for extracellular calcium (i.e. calcium influx) or mobilization of Ca2+ from cell reserves (e.B. sarcoplasmic reticulum and mitochondria). The source of the activation ion differs depending on the anatomical origin of the smooth vascular muscles, the contractile stimulus or the experimental conditions to which the tissues are exposed (Fig. 5-2). Contractile proteins are arranged in regular strands that explain the typical appearance of the sarcoma. Sarcomeres are divided into units bounded by I bands, which are halved by Z disks and A bands with a dark M in the middle. The I bands consist of thin filaments of actin, troponin and tropomyosin.

Thick filaments are made of myosin. The A-band consists of thin, thick overlapping filaments as well as other proteins. Several age-related changes in sarcomer contractile proteins have been reported, and some of the most characterized and clinically important are briefly discussed in this section. Although actin is an important contractile protein, the importance of the expression of its various isoforms during development remains uncertain. Hypertrophic cardiomyopathy is a primary disease of myofibrill contractile proteins. Basically, it is characterized by a significant thickening of the ventricular myocardium and a combination of hyperdynamic systolic function, obstruction of the left ventricular flow pathways and diastolic dysfunction with pulmonary venous congestion. More than 50% of cases of hypertrophic cardiomyopathy are hereditary (usually an autosomal dominant pattern with variable penetrance). Young patients experience a number of symptoms, including fatigue, exercise intolerance, chest pain, shortness of breath, syncope, and sudden death. Sudden death appears to be more common in children and young adults aged 10 to 35 years and often occurs before the disease is detected.72 About 40% of deaths occur during or shortly after vigorous physical activity; In other cases, patients were sedentary or engaged in light activities.

Hypertrophic cardiomyopathy appears to be the most common cause of sudden death in young athletes.74 Risk factors for sudden death include a family history of sudden death, a history of syncope, VT under Holter`s supervision, and, in children, excessive ventricular hypertrophy.73 The energy required for muscle contraction is provided by oxidation of carbohydrates or lipids. The term mechanochemical reaction has been used for this conversion of chemical energy into mechanical energy. It is known that the molecular process underlying the reaction involves fibrous muscle proteins whose peptide chains undergo a change in conformation during contraction. Contractile proteins are proteins that are involved in the sliding of contractile fibers (contraction) of the cytoskeleton of a cell, as well as the heart and skeletal muscles. Cardiac and muscle contraction fibers are bundles of actin polymers that slide side by side through the activity of the motor protein myosin and associated contractile proteins such as troponin and titin. The specific sites and functions of contractile proteins are listed in Table 5-1. Myofibrils (Figure 5-3D) are long cylindrical organelles with a diameter of 1 μm that contain the networks of contractile proteins responsible for the production of labor, force generation and shortening. Each myofibril is a column of sarcomeres, the contractile base units about 2.5 μm long and bounded by Z lines (Figure 5-3D and E) containing the densely packaged structural protein α actinin.

The contractile and structural proteins of each sarcomere form a highly ordered, almost crystalline network of thick, thin interdigitive myofilaments23 (Figure 5-3E, I and J). The myofilaments are remarkably uniform in length and lateral recording, even during contraction,24 resulting in a striated histological appearance of skeletal and cardiac muscles. This highly periodic organization has facilitated biophysical studies of muscles through sophisticated structural and spectroscopic techniques.25,26 Desmin reacts with parts of the muscle cell protein in the intermediate filament. In smooth muscle, desmin is located in the cytoskeleton region on dense bodies and dense plaques. In the static culture environment, SMCs gradually lose the contractile phenotype as the expression of genes such as desmin and myosin decreases in culture over the long term.22,44–46 However, the presence of insulin-like growth factor laminin,47 or β transforming growth factor (TGF-β) and mechanical stress48 have been shown to prevent the spontaneous loss of the contractile CMS phenotype in vitro. . . .