Physical activity relies on muscular force. In adult skeletal muscle, force results from the contraction of postmitotic, multinucleated myofibres of different contractile and metabolic properties. Myofibres can adapt to (patho-)physiological conditions of altered functional demand by radial growth, longitudinal growth, and regulation of fibre type functional gene modules. The adaptation's specificity depends on the distinct molecular and cellular events triggered by unique combinations of conditional cues. In order to derive effective and tailored exercise prescriptions, it must be determined (1) which mechano-biological condition leads to what molecular/cellular response, and (2) how this molecular/cellular response relates to the structural, contractile, and metabolic adaptation. It follows that a thorough mechano-biological description of the loading condition is imperative. Unfortunately, the definition of (resistance) exercise conditions in the past and present literature is insufficient. It is classically limited to load magnitude, number of repetitions and sets, rest in-between sets, number of interventions/week, and training period. In this review, we show why the current description is insufficient, and identify new determinants of quantitative and/or qualitative effects on skeletal muscle with respect to resistance exercise in healthy, adult humans. These new mandatory determinants comprise the fractional and temporal distribution of the contraction modes per repetition, duration of one repetition, rest in-between repetitions, time under tension, muscular failure, range of motion, recovery time, and anatomical definition. We strongly recommend to standardise the design and description of all future resistance exercise investigations by using the herein proposed set of 13 mechano-biological determinants (classical and new ones).

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New fundamental resistance exercise determinants of molecular and cellular muscle adaptations

Introduction of macromolecules into cultured mammalian cells by osmotic lysis of pinocytic vesicles.

The historical and current research literature is reviewed with special attention to the role of the satellite cell in the reconstitution of skeletal muscle following damage. Implications for the clinical management of trauma patients are stressed in the light of this new knowledge.

Skeletal muscle regeneration

1. The ability of a number of carboxylic acids, their esters, retinol and alpha-tocopherol to induce fusion of hen erythrocytes in vitro was investigated. 2. Some 30 different fat-soluble substances (100mug/ml) were found to cause the formation of multinucleated erythrocytes with a suspension of 3x10(8) erythrocytes/ml. The most effective agents induced fusion within 5-10min at 37 degrees C; some substances required about 1h. 3. Inclusion of Dextran 60C in the test medium minimized colloid osmotic lysis caused by exogenous lipids that induce cell fusion. 4. Cell swelling, followed by cell adhesion, was then seen to precede cell fusion. 5. Fusion occurred with C(10)-C(14) saturated carboxylic acids, with unsaturated, longer-chain carboxylic acids and their mono-esters; retinol, and to a lesser extent alpha-tocopherol, also caused cell fusion. 6. C(6)-C(9), C(15), C(16) and C(18) saturated carboxylic acids did not induce fusion within 4h; glyceryl dioleate was only weakly active, and glyceryl trioleate was inactive in the test system. 7. Fusion was facilitated by a high ratio of chemical agents to cell number and by incubation between pH5 and 6. It was inhibited by EDTA and by serum albumin. 8. Glyceryl mono-oleate caused both a similar fusion of several species of mammalian erythrocyte and the interspecific fusion of human and chicken erythrocytes. 9. The term ;fusogenic' is proposed to describe chemical, viral and physical agents that cause membranes to fuse. 10. The biochemical mechanisms involved and the possible biological significance of membrane fusion by fusogenic lipids are discussed.

/pdf/the-fusion-of-erythrocytes-by-fatty-acids-esters-retinol-and-2ud3l4uza9.pdf

The fusion of erythrocytes by fatty acids, esters, retinol and α-tocopherol

Publisher Summary This chapter discusses the structure and properties of the cell surface coat. Cell surface coats have been found on all living cells that have been examined with sufficiently sensitive methods. These cells protect their fragile plasma membrane with a relatively strong, hydrophilic coat which is a permanent feature of the cell surface complex. Under special conditions, however, rarely and momentarily, these coats can be breached or even removed from certain cells to reveal the delicate, oily, liquid like layer of the plasma membrane, damage to which is lethal unless immediately repaired. These cells usually are able to replace their missing coats in a matter of minutes. Most animal cell coats appear in the electron microscope (EM) as a uniform layer at the external cell surface. The layer seems to originate at, or be a part of, the outer leaflet of the trilaminar plasma membrane, and usually is 100-200 A thick. A variety of methods has been developed to reveal the ultrastructure of cell coats, the details of which depend on the particular method employed. The strength or durability of the cell surface coat varies dramatically among various cells.

The Structure and Properties of the Cell Surface Coat

A methodology for micromanipulating human cells of normal and malignant origin, in vitro, has evolved from the study of about 2000 HeLa, ERK (a subline of HeLa cells), and human embryonic lung cells during interphase and mitosis. It is now possible to microinject interphase cells with aqueous and nonaqueous fluids intracytoplasmically. Chromosomes from human embryonic lung metaphase cells have been transplanted. Chromosomes have been manipulated within mitotic human embryonic lung, ERK, and HeLa cells. Clones have been obtained from HeLa cells subjected to such manipulation. Predictable derangements of mitotic cells and their progeny have been obtained. Intranuclear injections of silicone oil, DNA, and sodium chloride solutions have been made with survival of the cells. HeLa cells have been cloned from such injected cells. Subcellular fractions have been introduced into the nuclei and cytoplasms of HeLa and human embryonic lung cells. The lung cells have been subjected to nuclear micropuncture in groups and a clone has been obtained. Virus suspensions have been introduced into the nuclei of HeLa cells without killing the cells. Applications of this methodology are discussed.

A Microsurgical Methodology for Human Cells in Vitro: Evolution and Applications

This article describes the equipment and microsurgical procedures requisite to dissecting, injecting or otherwise altering human cells of normal or malignant origin. These procedures, amenable to automation, are also requisite to the isolation and cloning of solitary, operated HeLa cells.

Microsurgical Studies on Human Cells and Cloning of HeLa Cells

The electrical properties of structures within an intact cell were examined by impalement with micropipette electrodes. Mean potential differences (PDs) measured from interphase HeLa cells showed that internal membrane-bounded compartments such as the nucleus, Golgi region, and the mitochondria were more negative than the cytoplasm with respect to an external grounding electrode. The nuclear PDs, unlike Golgi and cytoplasmic PDs, shifted during interphase and reached a peak value shortly before mitosis. The positioning of micropipettes was confirmed by electron microscope examination of marker solutions that were microinjected into specific intracellular regions. The combination of methods described here offers a new approach for the study of physiological events within intact, living cells.

https://rupress.org/jcb/article-pdf/72/1/86/1387431/86.pdf

The electrophysiological mapping of compartments within a mammalian cell.

Chromosomes of HeLa, ERK, and human embryonic lung cells have been manipulated at different mitotic stages. A method for releasing chromosomes from metaphase human embryonic lung cells has been developed and seven HeLa cell lines have been established from individual mitotic cells isolated and cloned after manipulation.

Chromosome Displacement in and Extraction from Human Cells at Different Mitotic Stages

Mammalian somatic-cell hybrids can be formed in a direct and precise manner by microsurgery. Fusion of cells brought about in this way permits selection of specific, identifiable cells of the same or different types or species and their fusion at telophase.

Elaine G. Diacumakos

Papers

A Microsurgical Methodology for Human Cells in Vitro: Evolution and Applications

Microsurgical Studies on Human Cells and Cloning of HeLa Cells

The electrophysiological mapping of compartments within a mammalian cell.

Chromosome Displacement in and Extraction from Human Cells at Different Mitotic Stages

Fusion of mammalian somatic cells by microsurgery.