A silver-reducing component in rat striated muscle

Summary In previous work on rat striated muscle cells a sliver-reducing component was found selectively localized at the terminal cistern/transverse tubule system (Tandler and Pellegrino de Iraldi 1989). To further investigate that problem we performed the Hg–Ag argentaffin reaction on a sarcoplasmic reticulum fraction from rat skeletal muscle. Circular profiles corresponding to vesicular structures were found outlined by silver grains. The number of silver stained vesicles were less than the total number vesicles stained by conventional procedures. The correlation between argentaffinities in the intact muscle fiber and their subcellular organelles indicated that the Hg–Ag reactive vesicles must be those derived from the terminal cisternae of the sarcoplasmic reticulum. The silver-reducing constituent aggregates in the presence of 1 mM CaCl₂ or 0.5 M K cacodylate. The state of aggregation induced by Ca²⁺ was not affected by incubation with 0.5% Triton X-100 or by 2 mM EDTA, thus suggesting a localization at or near the membrane of the terminal cistern vesicle facing the junctional gap. In Laemmli SDS-acrylamide gels the Hg–Ag reaction stained all proteins in a manner similar to Coomasie blue. It is suggested that the selective histochemical staining is the result of differential reactivities due to steric requirements of the chemical reaction.     

MCT1 confirmed in rat striated muscle mitochondria.

We sought to test the hypothesis that monocarboxylate transporter isoform 1 (MCT1) is the inner mitochondrial membrane lactate/pyruvate transporter, and, as such, contributes to functioning of the intracellular lactate shuttle. However, presence of a mammalian mitochondrially localized MCT1 (mMCT1) has been contested. We sought to confirm by Western blotting the mitochondrial localization of MCT1 in rat cardiac, soleus, and extensor digitorum longus muscles utilizing three different cell fractionation methods and three different antibodies. We performed Western blotting using antibodies to cell membrane glucose transporter isoform GLUT1, inner mitochondrial constituent cytochrome oxidase, the monocarboxylate transporter protein chaperone CD147, as well as custom and commercially available MCT1 antibodies. Western blots demonstrated similar results with each MCT1 antibody and two of three methods of fractionation. MCT1 was found in the mitochondria, as well as in the sarcolemmal membrane and whole muscle homogenates. Probing with GLUT1 and CD147 demonstrated that mitochondrial fractions were not contaminated with sarcolemmal remnants. Probing with cytochrome oxidase showed mitochondrial localization of MCT1. Comparison of these results to the findings of others indicates that the most likely source of discrepancy is the cell fractionation procedure utilized.     

Fatty acids in the development and stabilization of the rat brain

The development of the rat's brain demonstrates the increase of the short, medium and long C-chain saturated fatty acids and of the docosahexaenoic acids and the decrease of the mono-unsaturated fatty acids, of the linoleic-arachidonic acids, of the alpha-linolenic-eicosapentaenoic acids. The stabilization of the brain in the adult rat increases all the saturated and mono-unsaturated fatty acids and triene, while it decreases all the poly-unsaturated (omega-6; omega-3) fatty acids. The CCl4 poisoning cuts down the linoleic-arachidonic acids and the alpha-linolenic acid throughout the development of the rat's brain; after the growth, CCl4 increases triene, ac. eicosapentaenoic and reduces the linoleic-arachidonic and alpha-linolenic-ac. docosahexaenoic acids.     

Occurrence and regional distribution of striated muscle fibers in the rat pineal gland

Summary In a total of 96 rat pineals studied 31 were found to contain striated muscle fibers or their precursors. The muscle fibers were most frequently present in the stalk region and more frequently found in the left than in the right hemisphere. Size measurements revealed that the lengths of pineal muscle cell nuclei differ only slightly from those of the sphincter muscle of the iris. However, the yellowish appearance of pineal muscle cell nuclei under darkfield investigation, a phenomenon observed in all muscular tissues of mesenchymal origin and connective tissue cells, may support the hypothesis that pineal musculature is of mesenchymal rather than ectodermal origin.Supported by a grant (Vo 135/4) of the Deutsche Forschungsgemeinschaft within the Schwerpunktprogramm Neuroendokrinologie     

Contracting striated muscle fibres differentiated from primary rat pituitary cultures

Summary Whole pituitaries or adenohypophyses alone of adult female Wistar/ Furth rats were dissociated into single cells by means of two different enzymic disintegration methods. The single-cell suspension was then seeded out and cultured for up to 8 months in tissue culture dishes with untreated and polylysine coated surfaces. The cells were cultured in different sera (horse serum, newborn-calf serum, fetal-calf serum, mixtures of horse and newborn-calf serum, and isogenic rat serum) and also in a serum-free, hormone-supplemented medium. When the cells were cultured in medium containing horse serum (15 %) plus fetal-calf serum (3%) on polylysine-treated surfaces, cell fusion and the development of myotubes could be observed between day 5 and 10 after seeding and, on about day twenty, the formation of multicellular microstructures could be seen. Myotubes in such microstructures differentiate into muscle fibres, and show spontaneous contraction. Striation is visible both light and electron microscopyically. Such a differentiation into striated muscle cells depends on specific culture conditions: the serum used, the formation of microstructures, and the treatment of the culture dishes. There is apparently no previous report of striated muscle cells found in pituitary cultures.     

Interfilament forces in striated muscle

Evaluation of the Van der Waals energy per filament suggests that molecular dispersion forces should not be very important in determining the stability of the myofilament lattice in resting muscle. In order to explain the lattice stability and other important properties of the striated muscle, it is suggested that a balance between electrostatic forces and forces developed by some interfibrillar structures is mainly responsible.     

Esterases in striated muscle from mice with the Chediak-Higashi syndrome

In this paper a localized strong reaction for non-specific esterase forming cylindric structures is described within skeletal muscle fibres from the beige mouse. It seems from zymograms and protein electrophoresis that this esterase is membrane bound, highly reactive and present in rather small amounts within the muscle fibres.     

Immunoelectron microscopic localization of albumin in smooth and striated muscle tissues of rat

Summary Localization of serum albumin in the striated and smooth muscles of rat was studied by an improved immunocytochemical method. Diaphragm, ventricular myocardium, and smooth muscle of stomach were examined. In all of these tissues, albumin was found in the interstitial space and small subsarcolemmal caveolae and vesicles. In addition, the transverse tubular system of the striated muscle stained positive for albumin. The subsarcolemmal vesicles containing albumin did not show any evidence of fusion with lysosomes. Furthermore, in smooth muscle, most of these vesicles were open to the extracellular space. These results demonstrate that albumin in smooth and striated muscle is confined to the extracellular space suggesting that substances such as fatty acids which are carried by albumin are split from it and taken up at the level of the plasma membrane.     

Proteomic analysis of striated muscle

The techniques collectively known as proteomics are useful for characterizing the protein phenotype of a particular tissue or cell as well as quantitatively identifying differences in the levels of individual proteins following modulation of a tissue or cell. In the area of striated muscle research, proteomics has been a useful tool for identifying qualitative and quantitative changes in the striated muscle protein phenotype resulting from either disease or physiological modulation. Proteomics is useful for these investigations because many of the changes in the striated muscle phenotype resulting from either disease or changes in physiological state are qualitative and not quantitative changes. For example, modification of striated muscle proteins by phosphorylation and proteolytic cleavage are readily observed using proteomic technologies while these changes would not be identified using genomic technology. In this review, I will discuss the application of proteomic technology to striated muscle research, research designed to identify key protein changes that are either causal for or markers of a striated muscle disease or physiological condition.     

Fatty acids of phospholipids of brain cell nuclei in rat ontogenesis

Experiments were carried out on the 19-day old rat embryos, the 5- and 45-day old rat pups, and the 1.4–1.5-year old rats. Phospholipids and their fatty acid composition in brain cell nuclei were studied using methods of extraction, two-dimensional thin-layer chromatography, and spectrofluorimetry. In the course of ontogenesis, the percentage of different classes of nuclear phospholipids was changed; at the postembryonic period, the unsaturation index of lipids (phosphatidylcholine and phosphatidylethanolamine) and the content of unsaturated (especially polyenic) fatty acids decreased. Microviscosity of nuclear membranes increased; these changes were also shown earlier in phylogenesis of vertebrates. Thus, the facts revealed in the present work correspond to the recapitulation law. It is suggested that such change of lipid ratio and of composition of their fatty acids as well as of the membrane microviscosity serve for regulation of functions of membrane proteins and have adaptive character.