Ischemia-induced increase of stiffness of αB-crystallin/HSPB2-deficient myocardium

The two small heat shock proteins (sHSPs), B-crystallin and HSPB2, have been shown to translocate within a few minutes of cardiac ischemia from the cytosol to myofibrils; and it has been suggested that their chaperone-like properties might protect myofibrillar proteins from unfolding or aggregation during stress conditions. Further evidence of an important role for HSPs in muscle function is provided by the fact that mutations of the B-crystallin gene cause myopathy and cardiomyopathy. In the present study, we subjected isolated papillary muscles of B-crystallin/HSPB2-deficient mice to simulated ischemia and reperfusion. During ischemia in B-crystallin/HSPB2-deficient muscles, the development of contracture started earlier and reached a higher value compared to the wildtype mice. The recovery of contracture of B-crystallin/HSPB2-deficient muscles was also attenuated during the simulated reperfusion period. However, twitch force was not significantly altered at any time of the experiment. This suggests that during ischemic insults, B-crystallin/HSPB2 may not be important for the contraction process itself, but rather serve to maintain muscular elasticity.     

Activation of locomotor and grasping spine muscle fibres in chaetognaths: a curious paradox

Chaetognath muscle fibres resemble vertebrate muscle fibres in having an abundant sarcoplasmic reticulum (SR) and analogues of the transverse (T) tubular system, but contraction is regulated differently. In intact chaetognaths electrically-evoked contractions of the striated locomotor muscles were largely or totally blocked by d-tubocurarine, by surgical removal of the ventral ganglion and by Co²⁺. Contractions of single cells enzymatically dissociated from locomotor muscles were likewise blocked by Co²⁺, they twitched once only after calciseptine, showed neither contractures nor elevated intracellular Ca²⁺ with caffeine, and ryanodine did not block contractions. Whole cell voltage-clamped locomotor muscle cells displayed a typical inward rectified Ca²⁺ current that was sensitive to the Ca²⁺ channel blockers nifedipine and calciseptine and showed voltage-dependent activation with a threshold at –25 mV and a peak inward current at + 10 mV. In contrast, whole cell voltage-clamped cells from the muscles operating the grasping spines of the head showed an initial very rapid and rapidly-inactivating inward current abolished by tetrodotoxin (TTX), followed by a slower and slowly-inactivating inward current blocked by calciseptine. The relation between these observations and the unusual vertebrate-like structure of the muscle cells is discussed.     

Anticipatory postural changes induced by active unloading and comparison with passive unloading in man

Normal human subjects, sitting in a chair, were required to maintain stable elbow flexion against loads of 0.5 kg or 1.0 kg. Unloading was affected either passively by the experimenter, or actively with the subject's own contralateral arm. Elbow angle, force exerted by the load, and electromyographic activity (EMG) of biceps and triceps muscles of both arms were recorded and averaged. Passive unloading was followed by a reduction of biceps EMG activity, starting 50–80 ms after weight lift, and by an upward deflection of the forearm. With active unloading, however, a reduction of the biceps EMG activity slightly preceded the onset of unloading (0–30 ms). This reduction of the actively unloaded arm occurred at about the same time as the activity of the contralateral unloading arm. In this experiment, the unloaded forearm maintained an almost stable position. Thus, the anticipatory adjustment of elbow posture, observed when unloading was performed by the subject, appears to optimize limb stability during the mechanical perturbation.     

Antigenic similarity between the protein neurotoxin α-bungarotoxin and neuromuscular blocking drugs

The snake neurotoxins -bungarotoxin (-BGT) and -bungarotoxin (-BGT) which act at the neuromuscular junction, were found to bind to IgE antibodies directed against neuromuscular blocking (NMB) drugs in the sera of two patients who had experienced lifethreatening anaphylactic reactions to succinylcholine. -BGT inhibited IgE-binding to a choline-Sepharose solid support in one patient better than the NMB drug alcuronium, choline, triethylcholine and -BGT. IC₅₀s for -BGT and succinylcholine were 16 and 10 nmol respectively for one patient and 34 and 6.0 nmol for the other.Recognition of the NMB drugs and -BGT by the same antibody is the first demonstration of an antigenic similarity between these drugs and the protein toxin.     

Lack of myoblasts migration between transplanted and host muscles of mdx and normal mice

Summary Extensor digitorum longus muscles of normal mice (C57BL/10ScSn hereafter called C57) were orthotopically transplanted into dystrophin-deficient mice (mdx) and reciprocally, mdx Extensor digitorum longus muscles were transplanted into C57 mice. After an initial phase of degeneration, transplanted muscles regenerate nearly completely, as evaluated from the maximum isometric force of muscles isolated 60 days after the surgery. In other similar experiments, instead of isolating the grafted muscles, we excised the antero-external muscles of the leg, including the grafted muscle. Cryostat cross-sections at three levels along the muscles were immunostained with an anti-dystrophin antibody. No muscle cells of dystrophin-deficient muscles grafted into normal mice took the antibody except a few revertant fibres, while all the muscle cells of the normal host were immunostained. Reciprocally, all the muscles cells of normal grafts were stained, whilst no antibody stained the cells of the surrounding muscles of the dystrophin-deficient host. These experiments show that very few if any of the myoblasts or muscle precursor cells, active during the regeneration of grafted muscle, migrate into the adjacent muscles. These results could be explained by the absence, in our work, of injuries of the grafted and adjacent host muscles epimysium and the absence of extensive inflammatory reactions. This lack of myoblast mobility suggest that when myoblast transfer is applied to muscle therapy, it will be necessary to inject myoblasts within each muscle to obtain an efficient treatment.     

Neural and Mechanical Contributions to the Stretch Reflex: A Model Synthesis

A model for the soleus stretch reflex in the decerebrate cat was synthesized from models of the neural and muscular components, including the two proprioceptors (the muscle spindle and Golgi tendon organ) and their associated afferents (Ia, II, and Ib), the motoneuron pool with its reflex pathways, the branches of the motoneurons to the intrafusal muscles ( innervation), and the extrafusal muscle. Parameters for the muscle and receptor models were chosen independently to match their responses in isolation. Reflex gains and inputs were estimated to fit the response to stretch measured by Nichols and Houk. The chosen reflex gains and inputs are not unique; many different combinations reproduced the characteristic stretch response. With a single set of fixed parameters, the model predicted many mechanical properties of the stretch reflex, including linearization effects (when the stretch magnitude and direction are varied), as well as the dependence on operating force and initial muscle length. The model did not accurately predict the responses at higher stretch velocities, due to failure of the extrafusal muscle model. © 2002 Biomedical Engineering Society. PAC02: 8719Ff, 8719Rr, 8719La     

Activity in torso muscles during relaxed standing

Summary Electromyographic activity of erector spinae, external oblique, and rectus abdominis muscles was studied during relaxed standing compared to lying down. Activity in the forearm extensors and forearm flexors was also studied. Surface electrodes were used.Each of the torso muscles exhibited 0.2 V of activity and the forearm muscles 0.1 V while subjects were relaxed and lying down. During quiet standing the erector spinae, external oblique, and rectus abdominis muscles showed a median activity of 1.0 V, 2.5 V, and 0.7 V respectively (for a minimum of ten 10-sec samples per subject). Examination of the integrated records during standing revealed no periods without increased muscle activity in the torso muscles. By contrast, activity in the forearm muscles did not increase during standing.The major superficial muscles of posture in the torso appear to act as guy wires, being continually active during standing. There is no support for hypotheses of passive support for the torso, nor do torso muscles act in either/or fashion; both anterior and posterior muscles are active at once. There is no sign of generally increased muscle tone in all muscles or in extensors; only the postural muscles are continuously active.     

Translation enhancer in the 3′-untranslated region of rotavirus gene 6 mRNA promotes expression of the major capsid protein VP6

Summary. The eleven rotavirus mRNAs contain 5-cap structures and most end with the 3-consensus sequence 5-UGACC-3. The UGACC functions as a common translation enhancer (3-TE-con) that upregulates viral protein expression through a process mediated by the nonstructural protein NSP3. To address the possibility that gene-specific enhancers are also contained in the untranslated regions (UTRs) of the rotavirus mRNAs, we used rabbit reticulocyte lysates to investigate the translation efficiencies of analog RNAs containing viral-specific 5-and 3-UTRs and the open reading frame for chloramphenicol acetyltransferase. These experiments combined with the analysis of full-length viral RNAs and RNAs containing 3-truncations showed that a highly active enhancer was present near the 5-end of the 139-nucleotide 3-UTR of the gene 6 mRNA (3-TEg6). The 3-TEg6 represents a functionally independent enhancer, as no other portion of the gene 6 mRNA was required for its activity. The 3-TEg6 differs significantly from the 3-TE-con in that the gene 6-specific enhancer does not require viral protein for activity and is formed by a sequence unique to only one of the eleven viral mRNAs. Together, our findings suggest that the 3-UTR of the gene 6 mRNA contains two TEs, one is gene-specific (3-TEg6) and the other is common to nearly all rotavirus genes (3-TE-con). The activity of the 3-TEg6 is likely important for directing the efficient translation of the gene 6 mRNA at levels sufficient to provide the 780 copies of VP6 necessary for the assembly of each progeny virion.     

Structurally differentDrosophila striated muscles utilize distinct variants of Z-band-associated proteins

Summary Monoclonal antibodies raised against four proteins from insect asynchronous flight muscle have been used to characterize the cross-reacting proteins in synchronous muscle ofDrosophila melanogaster. Two proteins,-actinin and Z(400/600), are found at the Z-band of every muscle examined. A larger variant of-actinin is specific for the perforated Z-bands of supercontractile muscle. A third Z-band protein, Z(210), has a very limited distribution. It is found only in the asynchronous muscle and in the large cells of the jump muscle (tergal depressor of the trochanter). The absence of Z(210) from the anterior four small cells of the jump muscle demonstrates that cells within the same muscle do not have identical Z-band composition. The fourth protein, projectin, > 600 kDa polypeptide component of the connecting filaments in asynchronous muscle, is also detected in all synchronous muscles studied. Surprisingly, projectin is detected in the region of the thick filaments in synchronous muscles, rather than between the thick filaments and the Z-band, as in asynchronous muscles. Despite their different locations, the projectins of synchronous and asynchronous muscles are very similar, but not identical, as judged by SDS-PAGE and by peptide mapping. Projectin shows immunological cross-reactivity with twitchin, a nematode giant protein that is a component of the body wall A-band and shares similarities with vertebrate titin.     

Postural adjustments due to external perturbations during sitting in 1-month-old infants: evidence for the innate origin of direction specificity

The aim of the study was to examine whether infants, at an age when they have no or little experience in sitting, can produce direction specific postural adjustments, i.e. synergies of muscle activity on the ventral side of the body during backward sway and on the dorsal side during forward sway. In addition, we addressed the question whether postural adjustments at this young age are restricted to single muscle responses or consist of a variable repertoire of muscle activation patterns including one during which all direction specific muscles participate (complete pattern). Postural adjustments due to external perturbations in a sitting position were studied in eight healthy infants aged 1 month. Multiple surface EMGs of neck, trunk and leg muscles and kinematics were recorded while the infants were exposed to horizontal forward (Fw) and backward (Bw) displacements of the surface of support. Direction specific postural adjustments, defined as adjustments during which agonist activation or antagonist inhibition preceded antagonist activation, were present in 85% of Bw and 72% of Fw translations. The direction specific adjustments showed a large variability with the repertoire of adjustments including the activation of one, two or all of the recorded direction specific muscles. The finding of direction specific adjustments at 1 month of age support the opinion that the basic level of organisation of postural adjustments has an innate origin. The finding of a variable repertoire of muscle response patterns, including the complete pattern, refutes the idea that the development of postural adjustments results from gradual addition of appropriate muscles to the synergies.Electronic Supplementary Material Electronic supplementary material is available in the online version of this article at The study was supported financially by Folke Bernadotte Stiftelsen, Linnéa och Josef Carlssons Stiftelse, Norrbacka-Eugeniastiftelsen, Riksförbundet för Rörelsehindrade Barn och Ungdomar and Sunnerdahls Handikappfond     

Fish muscle structure: fibre types in flatfish and mullet fin muscles using histochemistry and antimyosin antibody labelling

Summary In studies of the myosin crossbridge interaction with actin in vertebrate muscles, the muscles of bony fish have the unique advantage for ultrastructural work that the A-band has a simple crystalline lattice of myosin filaments. However, the anatomy and physiology of these fish muscles is relatively poorly understood compared with the rabbit, chicken or frog muscles conventionally used for crossbridge studies. Here the fibre types in fish fin muscles have been characterized to allow sensible selection of single fish fibres for ultrastructural studies. The fibre type compositions of the fin muscles of mullet, plaice, sole and turbot were examined by histochemistry and immunohistochemistry using polyclonal antibodies raised against various myosin isoforms: fish slow, fish fast, mammalian fast (type IIA) and chicken tonic myosins. In the mullet, fin muscles were composed of variable proportions of fast and slow fibres. In the three flatfish, the fin muscle showed a zonal arrangement with slow fibres, binding anti-slow myosin antibody, next to the skin ( region). The bulk of the muscle, distal to the skin, was a typical fast muscle both histochemically and in its reaction with antibodies ( region). Between these two regions there may be one (sole) or two (turbot, plaice) intermediate zones ( and regions) comparable to the pink/intermediate layer of myotomal muscle. In the plaice fin muscle, two kinds of slow fibre could be distinguished immunohistochemically.     

Use of girth measurements for estimating body volume and body density in Indian girls aged 10–19 years

Summary Mean values and standard deviations of total body volume, body density, height, weight, and a battery of 20 girth measurements of 200 Punjabi girls aged 10–19 years are presented. Selective stepwise multiple regression equations for predicting total body volume and body density from girth measurements are also given for different age groups.Hip girth was the most commonly selected measurement at the first step in most age groups and the values of r between hip girth and total body volume ranged between 0.86–0.96 in different age groups. The values of multiple R between total body volume and a combination of first four selected girth measurements varied from 0.96–0.99 in different age groups.The values of multiple R between body density and a combination of four girth measurements selected up to fourth step ranged between 0.73–0.92 in different age groups.     

α-cardiac-like myosin heavy chain MHCIα is not upregulated in transforming rat muscle

The expression of MHCI, an -cardiac-like myosin heavy chain isoform, was studied in extensor digitorum longus (EDL) and tibialis anterior (TA) rat muscles undergoing fast-to-slow transition by chronic low-frequency stimulation (CLFS), a condition inducing a transient upregulation of MHCI in rabbit muscle. In order to enhance the transformation process, CLFS was applied to hypothyroid rats. mRNA analyses were performed by RT-PCR, and studies at the protein level by immunoblotting and immunohistochemistry, using the F88 antibody (F88 12F8,1) demonstrated in the accompanying paper to be specific for MHCI. In total RNA preparations from slow- and fast-twitch muscles, MHCI mRNA was present at minute levels, at least three orders of magnitude lower than in cardiac atrium. As verified immunohistochemically, MHCI is present only in intrafusal fibres of rat muscle. Moreover, MHCI is not expressed in extrafusal fibres and, contrary to the rabbit, was not upregulated at both the mRNA and protein levels by CLFS. These results support our notion of species-specific responses to CLFS. Another antibody reported to be specific to MHCI, BA-G5, was also investigated by immunoblot and immunohistochemical analyses. Its specificity could not be validated for skeletal muscles of the rat. BG-A5 was shown to cross-react with MHCIIb and MHCI. These results question an upregulation of MHCI in transforming rat muscles as reported in studies based on the use of this antibody.     

Suppressive regions in the visual receptive fields of single cells of the pigeon's optic tectum

Summary Intracellularly HRP-labelled cat hindlimb -motoneurones were reconstructed light microscopically from a series of 1 m or 2 m thick consecutive sections. The volume and surface area of the soma as well as the size of the very proximal part of the dendritic and axonal processes were estimated morphometrically. Similar measurements were also made on adjacent unlabelled neurons in the same series of sections. A close relation was found between the soma volume and surface area on one hand the combined cross-sectional area of the proximal dendrites and axon on the other. The combined axonal and dendritic bases occupied on the average 16% of the soma surface. The accuracy in using the diameters and cross-sectional area of the cell body as indirect estimates of soma volume and surface area was analyzed. Combined measurements in both the transversal and sagittal planes were then found to yield more satisfactory estimates then when the measurements were confined only to the transversal plane. Several different formulas using the soma axes for indirect calculations of the soma volume and surface area were compared with respect to the accuracy of the results.     

Rhythmic Photostimulation and the Number of α-Rhythm Dipoles in the Human Brain

The numbers of -rhythm equivalent current dipoles (ECD) arising in the human brain before and during rhythmic photostimulation at the -rhythm frequency was studied in six healthy adult subjects. Dipoles were calculated using a single-dipole model for the whole of the -range and three subranges by solution of inverse equations in a three-layer model of the head obtained by simultaneous use of EEG data and MRI tomograms of the subjects' heads. The number of apparent ECD was significantly associated with rhythmic photostimulation and depended on the phase of the -rhythm wave at which stimulation started and on the type of visual illusion (circle, spiral, grid) appearing during this time. The relationship between these data and the hypothetical wave process scanning the human visual cortex at the frequency of the -rhythm is discussed.     

Effects of hypoxia on passive electrical properties of canine ventricular muscle

The effect of hypoxia, either in the presence or in the absence of glucose, on the passive electrical properties of canine ventricular muscle fibers was examined, employing a single sucrose gap method. The significant changes after 30 min of hypoxia (PO ₂=35–45mm Hg) were an increase in the specific internal longitudinal resistance (R _i) and a decrease in the space constant (). The values during the control (PO ₂>450mm Hg) were 198±77 cm forR _i and 0.81±0.15 mm for , and they changed to 245±90 cm and 0.70±0.10mm, respectively, after 30min of hypoxia. Hypoxia decreased the specific membrane resistance (R _m), but the changes were not statistically significant. The membrane time constant ( _m ) and capacity (C{imm}) were not affected significantly. The absence of glucose during hypoxia was found to cause more profound changes than hypoxia alone in the passive electrical properties, especiallyR _i and , suggesting that glucose might counteract the effects of hypoxia on these parameters of ventricular muscles.     

Enhancement by TNF-α of reactivation and replication of latent herpes simplex virus from trigeminal ganglia of mice

Summary The influence of tumor-necrosis-factor- (TNF-), granulocytemacrophage colony-stimulating factor (GM-CSF), interleukine-1 (IL-1) and IL-3 on the in vitro reactivation frequency and replication rate of trigeminal ganglia of mice latently infected with herpes simplex virus (HSV) strain KOS was studied. It could be demonstrated that TNF- and possibility GM-CSF, but not IL-1 and IL-3, enhanced the reactivation frequency and replication of HSV. Interferon / (IFN/) prevented reactivation and replication.     

Immunohistochemical studies on S-100 cells in the anterior pituitary gland of Sprague Dawley rats and spontaneous dwarf rats

The S-100 cells in the pituitary glands of adult male Sprague Dawley rats (SDs) and spontaneous dwarf rats (SDRs) were immunohistochemically examined using anti-S-100 and anti-S-100 monoclonal antibodies. The immunoreactive cells against S-100 protein were divided into three subtypes on the basis of their immunore-activity against subunits of S-100 protein: S-100 dominant type (the -type cell), S-100 dominant type (the \-type cell) and immunoreactive against both S-100 and S-100 (the -type cell). In the SD, -type cells represented 26% of the total S-100 immunoreactive cells (S-100 cells) and were localized in the peripheral area of the ventral region of the pituitary gland. This type of cell was observed forming clusters, with more abundant cytoplasm than the -type cell. The proportion of -type cells was 53%. They were diffusely distributed throughout the gland, and their processes were thicker than those of the -type cell. In the SDR, the proportion of -type cells was 55%, and they were observed throughout the gland. In contrast, -type cells totalled 12% and were localized in small areas of the central and peripheral region of the gland. The proportion of -type cells was 21% in the SD and 33% in the SDR and they were observed forming small clusters in both animal groups. The proportion of -type cells compared with the total of S-100-immunoreactive cells was significantly higher (P < 0.05) in the SDR than in the SD, while the proportion of -type cells was markedly lower (P < 0.05).     

On the regulation of the expressed L-type calcium channel by cAMP-dependent phosphorylation

The Ca²⁺ channel subunits _1C-a and _1C-b were stably expressed in Chinese hamster ovary (CHO) and human embryonic kidney (HEK) 293 cells. The peak Ba²⁺ current (I _Ba) of these cells was not affected significantly by internal dialysis with 0.1 mM cAMP-dependent protein kinase inhibitor peptide (mPKI), 25 M cAMP-dependent protein kinase catalytic subunit (PKA), or a combination of 25 M PKA and 1 M okadaic acid. The activity of the _1C-b channel subunit expressed stably in HEK 293 cells was depressed by 1 M H 89 and was not increased by superfusion with 5 M forskolin plus 20 M isobutylmethylxanthine (IBMX). The _1C-a·₂·₂/ complex was transiently expressed in HEK 293 cells; it was inhibited by internal dialysis of the cells with 1 M H 89, but was not affected by internal dialysis with mPKI, PKA or microcystin. Internal dialysis of cells expressing the _1C-a·₂·₂/ channel with 10 M PKA did not induce facilitation after a 150-ms prepulse to +50 mV. The Ca²⁺ current (I _Ca) of cardiac myocytes increased threefold during internal dialysis with 5 M PKA or 25 M microcystin and during external superfusion with 0.1 M isoproterenol or 5 M forskolin plus 50 M IBMX. These results indicate that the L-type Ca²⁺ channel expressed is not modulated by cAMP-dependent phosphorylation to the same extent as in native cardiac myocytes.     

Synergistic effects of tumour necrosis factor-α and interferon-γ on feline haemopoietic progenitors

Pathogenic mechanisms that underlie feline leukaemia virus subgroup-C (FeLV-C) induced erythroid aplasia are unknown. FeLV-C infection is associated with higher serum levels of interferon- (IFN-) and tumour necrosis factor- (TNF-), which may act synergistically to cause haemopoietic suppression. In the present studies, the synergistic effects of TNF- and IFN- on feline bone marrow progenitors in vitro were evaluated. Bone marrow mononuclear cells from specific-pathogen-free cats were exposed to TNF- (100 and 200 pg/ml) and IFN- (100 or 200 units/ml), alone or in combination, for 2 h before plating for clonal assays of colony forming units. Our results show that TNF- and IFN- in combination caused marked suppression of feline colony forming units-erythroid (CFU-E), burst forming units-erythroid (BFU-E), and colony forming units-fibroblasts (CFU-F), whereas colony forming units-granulocyte/macrophage (CFU-GM) were minimally affected. The same concentrations of TNF- and IFN- alone had minimal effects on CFU-E, BFU-E and CFU-F. These results suggest that TNF- and IFN- may play a significant role in regulating haemopoiesis in cats and may be involved in the pathogenesis of erythroid aplasia in cats infected with feline leukaemia virus.