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PubMed2003

[Organization and innervation of striated muscle fibers of the striated sphincter in the rat].

OBJECTIVES: To determine the organization of striated muscle fibre (FMS) of the rat striated sphincter (SS) and to characterize the motor endplates (MEP). MATERIAL AND METHODS: The urethras of 30 male and female rats were studied. Two thousand hematein-eosin stained serial sections and 800 sections simultaneously stained for MEPs and nerve endings were studied. RESULTS: The SMFs of the SS are organized in the urethral wall in four symmetrical bands. MEPs are predominantly found in the cranial third of the SS (22 MEPs per section). Sixty sixteen per cent of MEPs were situated in the lateral regions. Motor units were composed of a maximum of five SMFs. CONCLUSION: The SMFs of the SS are organized in four symmetrical bands. Myoconnective insertions of SMFs emphasize the importance of the connective tissue in their contractile action. They are innervated by a single MEP, in the same way as skeletal striated muscle fibres. In the SS, MEPs are predominantly located laterally to the right and to the left. The specific organization of motor units suggests an original mechanism of reinforcement of muscle contraction of the SS.

Animals↗
PubMed1997

Smooth muscle heterogeneity: does the striated muscle model apply?

Smooth muscle cells are the major component of most smooth muscle tissue. Although the function of these tissues is known to differ, it has been generally assumed that the smooth muscle cells that make up these tissues are all the same. In striated muscle, individual fibers composed of unique contractile and regulatory proteins have unique mechanical properties. Smooth muscles also contain unique proteins. The hexamer myosin has multiple isoforms of its heavy and light chain subunits. Some of these differences result from alternate splicing of a single gene, while others result from multiple genes. At the tissue level, the presence of these isoforms is developmentally regulated and varies between tissues and species. There are numerous contradictory reports in the literature regarding possible unique regulation and function for the multiple myosin heavy and light chain isoforms. By extending molecular and mechanical methods beyond their normally used ranges, we have begun a series of experiments at the single smooth muscle cell level. Preliminary results show extreme heterogeneity of myosin isoforms between smooth muscle cells. In addition, preliminary results suggest that the ratio of the SM1 and SM2 MHC tail isoforms do not correlate with unloaded shortening velocity. However, there is a good correlation between the amount of SM2 MHC isoform present in the cell and the minimum length to which the cell can shorten. Thus, cells with a greater SM2 content appear to shorten more than cells with a lesser SM2 content. As with striated muscle, single-cell experiments may be required to determine the unique function of protein isoforms in smooth muscle tissues.

Animals↗
PubMed2002

Direct x-ray observation of a single hexagonal myofilament lattice in native myofibrils of striated muscle.

A striated muscle fiber consists of thousands of myofibrils with crystalline hexagonal myofilament lattices. Because the lattices are randomly oriented, the fiber gives rise to an equatorial x-ray diffraction pattern, which is essentially a rotary-averaged "powder diffraction," carrying only information about the distance between the lattice planes. We were able to record an x-ray diffraction pattern from a single myofilament lattice, very likely originating from a single myofibril from the flight muscle of a bumblebee, by orienting the incident x-ray microbeam along the myofibrillar axis (end-on diffraction). The pattern consisted of a number of hexagonally symmetrical diffraction spots whose originating lattice planes were readily identified. This also held true for some of the weak higher order reflections. The spot-like appearance of reflections implies that the lattice order is extremely well maintained for a distance of millimeters, covering up to a thousand of approximately 2.5-microm-long sarcomeres connected in series. The results open the possibility of applying the x-ray microdiffraction technique to study many other micrometer-sized assemblies of functional biomolecules in the cell.

Animals↗
PubMed1972

17 O nuclear magnetic resonance spectrum of H 2 17 O in frog striated muscle.

Whole striated muscles from the frog Rana esculenta were bathed in Ringer's solution enriched with H(2) (17)O; the muscle water was subsequently collected by vacuum distillation. The integrated intensity of the nuclear magnetic resonance (NMR) signal of (17)O in the muscle was measured to be approximately (3/4) of the signal observed in the distilled water. The phenomenon may arise either from immobilization of a population of the water molecules which may be a very small fraction or as much as (1/4) of the total, or may reflect tumbling of (1/3) of the water molecules in a compartment containing an anisotropic medium. Such an effect was demonstrated for H(2) (17)O using the model system of sodium linoleate in water.

Animals↗
PubMed2003

Functional importance of the carboxyl-terminal region of striated muscle tropomyosin.

Striated muscle tropomyosin (TM) interacts with actin and the troponin complex to regulate calcium-mediated muscle contraction. Previous work by our laboratory established that alpha- and beta-TM isoforms elicit physiological differences in sarcomeric performance. Heart myofilaments containing beta-TM exhibit an increased sensitivity to calcium that is associated with a decrease in the rate of relaxation and a prolonged time of relaxation. To address whether the carboxyl-terminal, troponin T binding domain of beta-TM is responsible for these physiological alterations, we exchanged the 27 terminal amino acids of alpha-TM (amino acids 258 -284) for the corresponding region in beta-TM. Hearts of transgenic mice that express this chimeric TM protein exhibit significant decreases in their rates of contraction and relaxation when assessed by ex vivo work-performing cardiac analyses. There are increases in the time to peak pressure and a dramatic increase in end diastolic pressure. In myofilaments, this chimeric protein induces depression of maximum tension and ATPase rate, together with a significant decrease in sensitivity to calcium. Our data are the first to demonstrate that the TM isoform-specific carboxyl terminus is a critical determinant of sarcomere performance and calcium sensitivity in both the whole heart and in isolated myofilaments.

Animals↗
PubMed1968

Tetanus toxin: fine structure localization of binding sites in striated muscle.

When striated muscle from mice poisoned with purified tetanus neurotoxin was incubated with tetanus antitoxin labeled with horseradish peroxidase and stained for peroxidase activity, an electron-opaque reaction product was found in the transverse and terminal sacs of the longitudinal elements of the sarcotubular system. Demonstration of toxin in this location suggests that it acts by interfering with contraction coupling or mechanisms of contraction-relaxation.

Animals↗
PubMed2006

Effects of streptozotocin-induced diabetes and physical training on gene expression of titin-based stretch-sensing complexes in mouse striated muscle.

In striated muscle, a sarcomeric noncontractile protein, titin, is proposed to form the backbone of the stress- and strain-sensing structures. We investigated the effects of diabetes, physical training, and their combination on the gene expression of proteins of putative titin stretch-sensing complexes in skeletal and cardiac muscle. Mice were divided into control (C), training (T), streptozotocin-induced diabetic (D), and diabetic training (DT) groups. Training groups performed for 1, 3, or 5 wk of endurance training on a motor-driven treadmill. Muscle samples from T and DT groups together with respective controls were collected 24 h after the last training session. Gene expression of calf muscles (soleus, gastrocnemius, and plantaris) and cardiac muscle were analyzed using microarray and quantitative PCR. Diabetes induced changes in mRNA expression of the proteins of titin stretch-sensing complexes in Z-disc (MLP, myostatin), I-band (CARP, Ankrd2), and M-line (titin kinase signaling). Training alleviated diabetes-induced changes in most affected mRNA levels in skeletal muscle but only one change in cardiac muscle. In conclusion, we showed diabetes-induced changes in mRNA levels of several fiber-type-biased proteins (MLP, myostatin, Ankrd2) in skeletal muscle. These results are consistent with previous observations of diabetes-induced atrophy leading to slower fiber type composition. The ability of exercise to alleviate diabetes-induced changes may indicate slower transition of fiber type.

Animals↗
PubMed2004

Physiological significance of troponin T binding domains in striated muscle tropomyosin.

Striated muscle tropomyosin (TM) plays an essential role in sarcomeric contraction and relaxation through its regulated movement on the thin filament. Previous work in our laboratory established that alpha- and beta-TM isoforms elicit physiological differences in sarcomeric performance. To address the significance of isoform-specific troponin T binding regions in TM, in this present work we replaced alpha-TM amino acids 175-190 and 258-284 with the beta-TM regions and expressed this chimeric protein in the hearts of transgenic mice. Hearts that express this chimeric protein exhibit significant decreases in rates of contraction and relaxation when assessed by ex vivo work-performing cardiac analyses. There are increases in time to peak pressure and in half-time to relaxation. These hearts respond appropriately to beta-adrenergic stimulation but do not attain control rates of contraction or relaxation. With increased expression of the transgene, 70% of the mice die by 5 mo of age without exhibiting gross pathological changes in the heart. Myofilaments from these mice have no differences in Ca(2+) sensitivity of percent maximum force, but there is a decrease in maximum tension development. Our data are the first to demonstrate that the troponin T binding regions of specific TM isoforms can alter sarcomeric performance without changing the Ca(2+) sensitivity of the myofilaments.

Actin Cytoskeleton↗
PubMed1995

Functional capillary organization in striated muscle.

In striated muscle, capillaries occur as independent network groups. Network architecture was quantitated in cremaster muscle of pentobarbital sodium-anesthetized hamsters in three age groups [51 +/- 1 (SE), 65 +/- 1, and 79 +/- 1 days old]. We observed that networks consist of independent subgroups of capillaries, called modules. Module architecture did not vary significantly with age during maximal dilation (Max, 10(-4) M adenosine): tissue area (A) = 1.87 +/- 0.16, 1.19 +/- 0.13, and 1.81 +/- 0.3 x 10(5) microns 2; total segment length (sigma L) = 3.07 +/- 0.23, 2.15 +/- 0.21, and 3.02 +/- 0.45 x 10(3) microns; and segment number (N) = 14.5 +/- 1.1, 9.9 +/- 1.1, and 12.6 +/- 1.6, at ages 51, 65, and 79 days, respectively. Max module architecture was not different at 65 days of age at a second site of known higher O2 inflow: A = 2.03 +/- 0.32 x 10(5) microns 2; sigma L = 3.07 +/- 0.47 x 10(3) microns; and N = 13.1 +/- 2.1. During control conditions (Rest) there was also no significant difference with age: A = 1.68 +/- 0.18, 1.15 +/- 0.19, and 1.64 +/- 0.24 x 10(5) microns 2; sigma L = 2.31 +/- 0.23, 1.91 +/- 0.33, and 2.82 +/- 0.37 x 10(3) microns; N = 10.2 +/- 1.0, 7.8 +/- 1.3, and 11.0 +/- 1.4, at ages 51, 65, and 79 days, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1990

[Essential polyunsaturated nutrients in the development of rat striated muscle].

The striated muscle of the rat demonstrates, throughout the growth, an increase of the short C-chain saturated and of the mono-unsaturated fatty acids; a decrease of the saturated and poly-unsaturated fatty acids and shows a great quantity of the hyper-unsaturated (eicosapentaenoic and docosaesaenoic) fatty acids. The supplementation with linoleic and alpha-linolenic acids induces some effects of stabilization of the poly-unsaturated fatty acids in the grown-up and adult rat.

Animals↗
PubMed1994

Low energy charge and high adenosine content in smooth muscle of human bladder in comparison with striated muscle.

This study determined the energy charge, adenosine and inosine content of human bladder smooth muscle in comparison with striated muscle of the same individual. Biopsies were obtained from 21 women who were subjected to urethrocystopexy because of urinary stress incontinence. We found that the ATP content of bladder smooth muscle was only about one-eighth of that of striated muscle. The energy charge of bladder smooth muscle was 0.78 +/- 0.13, which is low compared with striated muscle (0.92 +/- 0.02). The adenosine content of bladder smooth muscle was 6.7 times higher than striated muscle and the adenosine/ATP ratio was 1:9 compared with 1:450 for striated muscle. These findings were in accordance with our previous studies on uterine smooth muscle.

Adenosine↗
PubMed1990

Hair follicle nevus with hyperplasia of smooth and striated muscle.

We report a peculiar nevus which occurred on the left side of the chin of an 18-year-old male. It had been present for four years and had grown rapidly during the last year. Histologically, many hair follicles, smooth muscles, and striated muscles were found within the reticular dermis. The hair follicles were accompanied by mature sebaceous glands; numerous eccrine glands were seen in the middle and deep dermis. Immunohistochemical stain and phosphotungstic acid hematoxylin stain supported the fact that the muscles seen between the follicles were both smooth and striated. This nevus was considered to be a hair follicle nevus accompanied by hyperplasia of smooth muscles and striated muscles.

Adolescent↗
PubMed1996

Immunohistochemical study and western blotting analysis of titin-like proteins in the striated muscle of Drosophila melanogaster and in the striated and smooth muscle of the oligochaete Eisenia foetida.

The presence and distribution of titin-like proteins have been examined in transversely striated muscle of Drosophila melanogaster, in obliquely striated muscles (body wall and inner muscular layer of the pseudoheart) and smooth muscle (outer muscular layer of the pseudoheart) from the earthworm Eisenia foetida by means of Western blotting analysis, light microscopy immunohistochemistry, and electron microscopy immunogold labeling, using antibodies anti vertebrate (chicken) titin (3,000 kDa) and arthropod (D. melanogaster) mini-titin (twitchin or projectin) (700 kDa). To determine whether these antibodies immunoreact non-specifically against vertebrate titin, mouse skeletal muscle was also studied. As negative control, mouse smooth muscle was used. Immunoreaction to mini-titin was found in all the invertebrate muscles studied. For each of these muscles, Western blotting analysis of mini-titin showed a single band, at approximately 700 kDa. Electron microscopy immunolabeling to this protein was observed along the whole sarcomere length (A bands and I bands) in both transversely striated muscles of the insect and obliquely striated muscles of the earthworm, although the number of immunogold particles was more abundant in the insect muscles. Mini-titin immunolabeling was also observed in the smooth muscle cells that formed the outer layer of the earthworm pseudoheart although in lower amounts than in the obliquely striated muscle. The absence of true sarcomeres in the smooth muscle cells did not permit to determine the extension of mini-titin immunolabeling. No immunoreaction to this protein was found in the striated and smooth muscles of the mouse. Immunoreaction to titin was only observed in the mouse skeletal muscle, in which both A bands and I bands appeared immunolabeled. Present results show that mini-titin in the invertebrate muscles studied differs immunohistochemically from vertebrate titin and, in contrast with titin, mini-titin is also present in invertebrate smooth muscles.

Animals↗
PubMed1991

Multiple serotonin receptors on large arterioles in striated muscle.

In rat striated muscle, serotonin (5-hydroxytryptamine; 5-HT) constricts large arterioles (first-order; A1) via 5-HT2 receptor activation but dilates smaller arterioles via a 5-HT1-like receptor. In this preparation, A1 arterioles possess little basal tone. The purpose of this study was to determine if 5-HT would elicit A1 dilation if arteriolar tone was first induced. In anesthetized rats, A1 diameters of the cremaster muscle were measured via in vivo videomicroscopy. Topical application of angiotensin II caused a 26 +/- 3% constriction of the vessels. 5-HT dilated the preconstricted A1s by 36 +/- 7% while constricting normal tone A1s by 33 +/- 5%. This dilation was enhanced by blocking 5-HT2 receptors with LY53857, but abolished with methysergide, a 5-HT1 and 5-HT2 receptor antagonist indicating that the dilation was mediated by a 5-HT1-like receptor. Thus, A1 arterioles possess both 5-HT2 and 5-HT1-like receptors. The net result of 5-HT application in striated muscle, dilation or constriction, will depend on the initial tone of the vessels.

Angiotensin II↗