Heike Jäger

What is 'fascia'? A review of different nomenclatures

There are many different definitions of fascia. Here the three most common nomenclatures are compared, including that of the Federative International Committee on Anatomical Terminology (1998), the definition included in the latest British edition of Grays Anatomy (2008) and the newer and more comprehensive terminology suggested at the last international Fascia Research Congress (2012). This review covers which tissues are included and excluded in each of these nomenclatures. The advantages and disadvantages of each terminology system are suggested and related to different fields of application, ranging from histology, tissue repair, to muscular force transmission and proprioception. Interdisciplinary communication involving professionals of different fields is also discussed.

Regulation of mammalian Shaker‐related K+ channels: evidence for non‐conducting closed and non‐conducting inactivated states

1 Using the whole‐cell recording mode we have characterized two non‐conducting states in mammalian Shaker‐related voltage‐gated K+ channels induced by the removal of extracellular potassium, K+o. 2 In the absence of K+o, current through Kv1.4 was almost completely abolished due to the presence of a charged lysine residue at position 533 at the entrance to the pore. Removal of K+o had a similar effect on current through Kv1.3 when the histidine at the homologous position (H404) was protonated (pH 6.0). Channels containing uncharged residues at the corresponding position (Kv1.1: Y; Kv1.2: V) did not exhibit this behaviour. 3 To characterize the nature of the interaction between Kv1.3 and K+o concentration ([K+]o), we replaced H404 with amino acids of different character, size and charge. Substitution of hydrophobic residues (A, V and L) either in all four subunits or in only two subunits in the tetramer made the channel insensitive to the removal of K+o, possibly by stabilizing the channel complex. Replacement of H404 with the charged residue arginine, or the polar residue asparagine, enhanced the sensitivity of the channel to 0 mm K+o, possibly by making the channel unstable in the absence of K+o. Mutation at a neighbouring position (400) had a similar effect. 4 The effect of removing K+o on current amplitude does not seem to be correlated with the rate of C‐type inactivation since the slowly inactivating G380F mutant channel exhibited a similar [K+]o dependence as the wild‐type Kv1.3 channel. 5 CP‐339,818, a drug that recognizes only the inactivated conformation of Kv1.3, could not block current in the absence of K+o unless the channels were inactivated through depolarizing pulses. 6 We conclude that removal of K+o induces the Kv1.3 channel to transition to a non‐conducting ‘closed’ state which can switch into a non‐conducting ‘inactivated’ state upon depolarization.

SK2 encodes the apamin-sensitive Ca2+-activated K+ channels in the human leukemic T cell line, Jurkat

T cells express two different types of voltage‐independent Ca2+‐activated K+ channels with small (SK) and intermediate (IK) conductance that serve important roles in the activation of T lymphocytes. In contrast to the IK channels from T lymphocytes which are upregulated upon mitogen stimulation, SK channels of Jurkat T cells, a human leukemic T cell line, are constitutively expressed even in the absence of mitogenic stimulation. We have used patch‐clamp recordings from transfected or injected mammalian cells to show that the cloned SK2 channel demonstrates the biophysical and pharmacological properties of the majority of K(Ca) channels in Jurkat T cells. The cloned and native channels are voltage‐independent, Ca2+‐activated, apamin‐sensitive, show an equivalent voltage‐dependent Ba2+ block and possess a similar ion selectivity. In addition, we used the polymerase chain reaction to demonstrate the presence of SK2 mRNA in Jurkat T cells, whereas SK3 transcripts encoding the other cloned apamin‐sensitive SK channel were not detected. These data suggest that the voltage‐independent apamin‐sensitive K(Ca) channel in Jurkat T cells represents the recently cloned SK2 channel.

Regulation of a mammalian Shaker-related potassium channel, hKv1.5, by extracellular potassium and pH

Using the whole‐cell recording mode of the patch‐clamp technique we studied the effects of removal of extracellular potassium, [K+]o, on a mammalian Shaker‐related K+ channel, hKv1.5. In the absence of [K+]o, current through hKv1.5 was similar to currents obtained in the presence of 4.5 mM [K+]o. This observation was not expected as earlier results had suggested that either positively charged residues or the presence of a nitrogen‐containing residue at the external TEA+ binding site (R487 in hKv1.5) caused current loss upon removal of [K+]o. However, the current loss in hKv1.5 was observed when the extracellular pH, pHo, was reduced from 7.4 to 6.0, a behavior similar to that observed previously for current through mKv1.3 with a histidine at the equivalent position (H404). These observations suggested that the charge at R487 in hKv1.5 channels was influenced by other amino acids in the vicinity. Replacement of a histidine at position 463 in hKv1.5 by glycine confirmed this hypothesis making this H463G mutant channel sensitive to removal of [K+]o even at pHo 7.4. We conclude that the protonation of H463 at pH 7.4 might induce a pK a shift of R487 that influences the effective charge at this position leading to a not fully protonated arginine. Furthermore, we assume that the charge at position 487 in hKv1.5 can directly or indirectly disturb the occupation of a K+ binding site within the channel pore possibly by electrostatic interaction. This in turn might interfere with the concerted transition of K+ ions resulting in a loss of K+ conduction.

Interactions of N-terminal and C-terminal parts of the small conductance Ca2+ activated K+ channel, hSK3.

Ca2+ activated K+ channels modulate the afterhyperpolarization in neurons. Using a variety of different techniques we obtained information about the function of N- and C-terminal parts of the Ca2+-activated K+ channel, SK3. By means of the yeast two hybrid technique we found an interaction between N-C and N-N- terminal parts of SK3. The strong N-C and N-N interaction was specific for SK3 and could not be observed for SK1 and SK2. Possibly a homotetrameric assembly of SK3 is favored in tissues were all SK channels are expressed. In addition, the interaction in SK3 was independent of the length of the polymorphic glutamine repeat in the N-terminus of SK3. Electrophysiological investigations showed that expression of amino acids 1-299 of SK3 (SK3N_299) modified the 1-EBIO pharmacology of endogenous SK3 channels in PC12 cells without affecting the Ca2+-sensitvity. The activation by 0.5 mM 1-EBIO in cells expressing amino acids 1-299 of SK3 was reduced by 32% in comparison to control experiments. Considering the N-C interaction in yeast, we conclude that the sensitivity of SK3 channels to 1-EBIO was modified by N-C interactions with SK3N_299. Therefore we conclude that N-C interactions influence SK3 channel function.

Small Ca2+-Activated Potassium Channels in Human Leukemic T Cells and Activated Human Peripheral Blood T Lymphocytes

In human T lymphocytes patch-clamp experiments have revealed the expression of two major subtypes of SK channels. In excitable cells these channel types play significant roles in shaping excitablility

Contractile elements in muscular fascial tissue – implications for in-vitro contracture testing for malignant hyperthermia

Malignant hyperthermia is a dreaded complication of general anaesthesia. Predisposed individuals can be identified using the standardised caffeine/halothane in‐vitro contracture test on a surgically dissected skeletal muscle specimen. Skeletal muscle is composed of muscle fibres and interwoven fascial components. Several malignant hyperthermia‐associated neuromuscular diseases are associated with an altered connective tissue composition. We analysed adjacent fascial components of skeletal muscle histologically and physiologically. We investigated whether the fascial tissue is sensitive to electrical or pharmacological stimulation in a way similar to the in‐vitro contracture test for diagnosing malignant hyperthermia. Using immunohistochemical staining, α‐smooth muscle actin‐positive cells (myofibroblasts) were detected in the epi‐, endo‐ and perimysium of human fascial tissue. Force measurements on isolated fascial strips after pharmacological challenge with mepyramin revealed that myofascial tissue is actively regulated by myofibroblasts, thereby influencing the biomechanical properties of skeletal muscle. Absence of electrical reactivity and insensitivity to caffeine and halothane suggests that, reassuringly, the malignant hyperthermia diagnostic in‐vitro contracture test is not influenced by the muscular fascial tissue.

A Shaker homologue encodes an A-type current in Xenopus laevis

In Xenopus laevis, several distinct K(+)-channels (xKv1.1, xKv1.2, xKv2,1, xKv2.2, xKv3.1) have been cloned, sequenced, and electrophysiologically characterized. K(+)-channels significantly shape neuronal excitability by setting the membrane potential, and latency and duration of action potentials. We identified a further Shaker homologue, xKv1.4, in X. laevis. The open reading frame encodes a K(+)-channel that shares 72% of its 698 amino acids with the human Shaker homologue, hKv1.4. Northern blot analysis revealed xKv1.4 in the brain, muscle, and spleen but not in the ovary, intestine, heart, liver, kidney, lung, and skin. Whole-cell patch clamp recording from rat basophilic leukaemia (RBL) cells transfected with xKv1.4 revealed a voltage-gated, outward rectifying, transient A-type, K(+) selective current. xKv1.4 was strongly dependent on extracellular K(+). Exposure of cells to K(+) free bath solution almost completely abolished the current, whereas in the presence of high K(+), inactivation in response to a maintained depolarizing step and the frequency-dependent cumulative inactivation decreased. Ion channels encoded by xKv1.4 are sensitive to 4-aminopyridine and quinidine but insensitive to tetraethylammonium and the peptide toxins, charybdotoxin, margatoxin, and dendrotoxin. In conclusion, our results indicate that the biophysical and pharmacological signature of xKv1.4 closely resemble those of the A-current described in Xenopus embryonic neurons and is similar to the human Shaker homologue, hKv1.4.

Faszien und ihre Bedeutung für die Interozeption

Zusammenfassung Den meisten Manualtherapeuten ist die nozizeptive und propriozeptive Bedeutung der Faszien nicht neu. Zusatzlich sind fasziale Gewebe jedoch auch mit zahlreichen freien Nervenendigungen versehen, die eine interozeptive Funktion haben. Diese projizieren zur Insula des Kortex, ein Areal das bei Primaten auf einmalig direkte Weise mit den peripheren Endigungen verbunden ist. Hier werden Korperempfindungen, die mit physiologischen Bedurfnissen assoziiert sind, mit emotionalen Farbungen verknupft (Temperatur, Eingeweideaktivitat, Hunger, muskulare Anstrengung, Vasomotorik etc.). Einige Pathologien hangen interessanterweise eher mit einer gestorten Interozeption zusammen als mit einer gestorten Sensomotorik; hierzu gehoren u.a. posttraumatische Belastungsstorung, Reizdarm, Depression, Angstneurosen, schizoide Storungen, Alexithymie (Gefuhlsblindheit) und Essstorungen. Das folgende Kapitel aus dem „Lehrbuch Faszien” gibt einen Uberblick uber den derzeitigen Stand des relativ neuen Forschungsgebietes, mit besonderer Berucksichtigung der fur Komplementartherapeuten relevanten Aspekte.

Evidence for the interaction of endophilin a3 with endogenous Kca2.3 channels in PC12 cells.

Background/Aims: Small-conductance calcium-activated (SK) channels play an important role by controlling the after-hyperpolarization of excitable cells. The level of expression and density of these channels is an essential factor for controlling different cellular functions. Several studies showed a co-localization of KCa2.3 channels and Endophilin A3 in different tissues. Endophilin A3 belongs to a family of BAR- and SH3 domain containing proteins that bind to dynamin and are involved in the process of vesicle scission in clathrin-mediated endocytosis. Methods: Using the yeast two-hybrid system and the GST pull down assay we demonstrated that Endophilin A3 interacts with the N-terminal part of KCa2.3 channels. In addition, we studied the impact of this interaction on channel activity by patch clamp measurements in PC12 cells expressing endogenous KCa2.3 channels. KCa2.3 currents were activated by using pipette solutions containing 1 µM free Ca2+. Results: Whole-cell measurements of PC12 cells transfected with Endophilin A3 showed a reduction of KCa2.3 specifc Cs+ currents indicating that the interaction of Endophilin A3 with KCa2.3 channels also occurs in mammalian cells and that this interaction has functional consequences for current flowing through KCa2.3 channels. Since KCa2.3 specific currents could be increased in PC12 cells transfected with Endophilin A3 with DC-EBIO (30 µM), a known SK-channel activator, these data also implicate that Endophilin A3 did not significantly remove KCa2.3 channels from the membrane but changed the sensitivity of the channels to Ca2+ which could be overcome by DC-EBIO. Conclusion: This interaction seems to be important for the function of KCa2.3 channels and might therefore play a significant role in situations where channel activation is pivotal for cellular function.