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.     

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.     

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.     

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.     

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).     

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.     

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.     

Lichtmikroskopische Untersuchungen über die Entwicklung vonTheileria annulata (Dschunkowsky und Luhs, 1904) inHyalomma anatolicum excavatum (Koch, 1844)

Summary Fully differentiated kinetes, average length 17.6m, appeared in the haemolymph of engorged nymphs usually 17 to 20 days after repletion. Kinetes were observed at first in the salivary glands on day 18 after repletion. The kinetes then transformed into fission bodies of about 10m in diameter, mainly in type III alveoli and less frequently in type II alveoli. The fission bodies grew up to a size of about 20m after several divisions of their nucleus. At this time the ticks moulted and no further development occurred until activation. Shortly before infestation the salivary glands began to proliferate, and rapid growth of the fission bodies was observed, especially in young ticks where development of infective particles (sporozoites) was concluded within two days. Development in feeding adult ticks apparently occurred in four major steps: (1) Division of primary fission bodies (sporonts) into numerous secondary fission bodies (primary sporoblasts), (2) division of secondary fission bodies into tertiary fission bodies (secondary sporoblasts), (3) production of particles (sporozoites) by tertiary fission bodies and release of particles into the saliva, and (4) degeneration of fission bodies and their host cell but further release of particles.The host cell was stimulated to giant growth, thus its diameter increased, on average, from 15 to 110 m. Heavy infections resulting from parasitaemias of >40% caused disease and mortality in the tick population. Development was much retarded by aging. In ticks starved for six months sporozoites did not develop before day five to seven of infestation. Sporozoites may not develop at all in six to nine month old female ticks during the infestation period. The significance of the described developmental stages ofT. annulata was discussed and a sexual generation postulated. The hypothetic development ofT. annulata in its tick vector was illustrated.

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Gefördert von der Deutschen Forschungsgemeinschaft (DFG)     

Effect of lysolecithin on blood vessel reactivity and of some ethers and esters of glycerophosphocholine and phosphocholine,respectively, on aggregation of rat platelets

Infusion of lysolecithin (LPC; e.g. 88 g/ml for 0.5–1.0 min) did not significantly impair the vasopressor action of norepinephrine (NE), prostaglandin F₂ (PGF₂) and extract of posterior pituitary (EPP) in the isolated perfused hind legs of rats. In other words, vascular smooth muscle behaves differently from the smooth muscle of the guinea-pig small intestine, since, in the latter, contractions evoked by acetylcholine, prostaglandins etc., are inhibited by LPC. Triton X 100 which, by comparison, was used as a detergent effective on the guinea-pig small intestine, depressed the vasopressor effect of NE, PGF₂ and EPP.LPC, at low concentrations (40 mol/l), potentiated (15% max.) ADP-induced platelet aggregation (PA) in rat PRP but, at high concentrations, inhibited PA (IC₅₀=390 mol/l). 2-Hexadecylglycerophosphocholine and its short-chain 1-alkyl ethers, which are structurally related to platelet-activating factor, as well as some long-chain alkanol phosphocholine esters, were somewhat more active than LPC. Dipalmitoyllecithin (4–700 mol/l) was without any effect.     

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.     

A comparative study of skeletal and cardiac tropomyosins

Summary The subunit composition, the thiol group content and the biological activities of cardiac tropomyosin (TM) of various animal species were compared. Cardiac TM from small animals such as rabbit, guinea-pig, rat and dog contain 2 SH/mole and were resolved into one band on SDS and acid urea electrophoresis and into two bands on alkaline urea electrophoresis. Chicken cardiac TM likewise gave one band and it contains 4 SH/mole. In contrast pig, sheep and human cardiac TM contain respectively 2.6, 2.4, and 2.4 SH/mole and were resolved into two bands and on the different electrophoresis systems used, with a : ratio respectively of I:4.2, I:4.6, I:4.8. The -TM components from sheep skeletal and pig and sheep cardiac muscles were more positively charged than the rabbit skeletal -TM component, as shown in alkaline urea electrophoresis system. The and combinations of dimers found for skeletal muscle by other authors, were also found for cardiac pig TM.All the TM have the same effect on the Ca²⁺-stimulated ATPase activity of desensitized actomyosin (DAM) and on the Mg²⁺-stimulated ATPase activity of DAM with troponin-complex.This work suggests that the subunits of the TM from skeletal and cardiac muscles are heterogenous in their M.W. and their charges and that in the heart as well as in skeletal muscle a relationship seems to exist between the amount of the component and the speed of contraction of the muscle: a higher amount of this component was found in the bulky hearts which are also those which contract slower.     

Developmental transitions in the myosin patterns of two fast muscles

Summary Transitions in myosin patterns were examined in situ by immunofluorescence in two fast muscles of the developing chicken, the pectoralis and the posterior latissimus dorsi. Myosin isoforms were localized using stage-specific monoclonal antibodies against the heavy chain of pectoralis myosin. Two antibodies (12C5 and 10H10) recognize adult and late embryonic myosin. They reacted weakly with both the pectoralis and posterior latissimus dorsi at 10 days in ovo, but intensely at 18 days in ovo. Both muscles were completely unreactive with an adult-specific antibody (5C3), indicating that the staining with 12C5 and 10H10 at 18 days in ovo reflects embryonic myosin. Thus two different embryonic isoforms are expressed sequentially in each muscle. Both 12C5 and 10H10 reacted weakly again with these muscles after hatching. The reappearance of a strong positive response to both antibodies, at 28 days in the pectoralis and after 60 days in the posterior latissimus dorsi, correlated well with the first appearance of a response to the adult-specific antibody, 5C3, signalling the beginning of the adult pattern. Both muscles reacted strongly with an antibody (5B4) specific for neonatal myosin between 18 days in ovo and 60 days after hatching. In the pectoralis, embryonic was replaced by neonatal myosin in most fibres by 14 days after hatching; by 28 days, both adult and neonatal myosin were expressed in most fibres; and in the adult, neonatal myosin was replaced entirely by the adult isoform. In contrast, many fibres in the posterior latissimus dorsi still expressed both embryonic and neonatal myosins up to at least 60 days post-hatch, and the remaining fibres expressed the neonatal isoform; the neonatal isoform was present in some fibres even in the adult posterior latissimus dorsi. We have therefore demonstrated in situ four different heavy chain isoforms in two different fast muscles. Early embryonic, late embryonic, neonatal and eventually adult isoforms are expressed in each muscle and more than one isoform often coexists in the same fibre.     

Activation of the skeletal α-actin promoter during muscle regeneration

Little is known conerning promoter regulation of genes in regenerating skeletal muscles. In young rats, recovery of muscle mass and protein content is complete within 21 days. During the initial 5–10 days of regeneration, mRNA abundance for IGF-I, myogenin and MyoD have been shown to be dramatically increased. The skeletal -actin promoter contains E box and serum response element (SRE) regulatory regions which are directly or indirectly activated by myogenin (or MyoD) and IGF-I proteins, respectively. We hypothesized that the skeletal -actin promoter activity would increase during muscle regeneration, and that this induction would occur before muscle protein content returned to normal. Total protein content and the percentage content of skeletal -actin protein was diminished at 4 and 8 days and re-accumulation had largely occurred by 16 days post-bupivacaine injection. Skeletal - actin mRNA per whole muscle was decreased at day 8, and thereafter returned to control values. During regeneration at day 8, luciferase activity (a reporter of promoter activity) directed by –424 skeletal -actin and –99 skeletal -actin promoter constructs was increased by 700% and 250% respectively; however, at day 16, skeletal -actin promoter activities were similar to control values. Thus, initial activation of the skeletal - actin promoter is associated with regeneration of skeletal muscle, despite not being sustained during the later stages of regrowth. The proximal SRE of the skeletal -actin promoter was not sufficient to confer a regeneration-induced promoter activation, despite increased serum response factor protein binding to this regulatory element in electrophoretic mobility shift assays. Skeletal -actin promoter induction during regeneration is due to a combination of regulatory elements, at least including the SRE and E box. © Kluwer Academic Publishers.     

Fibre types inLimulus telson muscles: morphology and histochemistry

Summary Using a variety of techniques, we have demonstrated the presence of at least two fibre types inLimulus median telson levator muscle. By light and electron microscopy, large (21 56 m² mean cross-sectional area) fibres have A-bands of 4.1 m, one-half I bands of 2.15 m and Z lines 0.5 m in width. Few mitochondria are found in these fibres, which comprise 54% of those present in a given microscope field and which occupy 82% of the total cross-sectional area. Small fibres (484 m² mean cross-sectional area) have A bands of 6.3 m, one-half I bands of 3.1 m and Z lines between 0.5 and 1.0 m in width and are rich in mitochondria. Although small fibres comprise nearly one-half (46%) of the fibres in a field, they occupy only 18% of the total cross-sectional area.Histochemical staining for alkaline-stable myofibrillar ATPase activity and mitochondrial reduced -nicotinamide adenine nucleotide (-NADH) tetrazolium reductase activity confirms the presence of two fibre types. The large fibres react positively for the myofibrillar ATPase activity and negatively for the mitochondrial enzyme activity. The reverse is seen with the small fibres. Some fibres of intermediate size, having intermediate staining characteristics, were also observed. Native gel electrophoresis of both myofibrillar and purified myosin preparations supports the observed differences in myofibrillar ATPase activity in that two myosin isozymes are resolved on pyrophosphate gels. Although the thick filaments isolated from unstimulated small fibres are longer (>6.0 m) than those isolated from unstimulated large fibres (4.26 m), all have a similar appearance with respect to the arrangement of myosin heads on their surfaces, and similar diameters. The implications of the observed heterogeneity of fibre types is discussed with reference to previously reported phenomena inLimulus telson muscle, including changes in length of thick filaments on fibre stimulation and the shape of the length-tension curve obtained from fibre bundles.     

The effects of thyroid status on some properties of rat fast-twitch muscle

Summary The effects of different thyroid states on some histochemical and biochemical properties of fast-twitch muscle were studied using rat extensor digitorum longus (EDL) muscle. This muscle was found to be much less responsive to thyroidal influence than the slow-twitch soleus muscle. In EDL muscles of hypothyroid rats, fast slow conversions were observed in fibre type composition, myosin ATPase activity and light chain pattern, and in the subunit composition of lactate dehydrogenase, while the only significant slow fast conversion observed in thyrotoxicosis was a decrease in the proportion of slow-oxidative fibres. Denervation of the hypothyroid muscle produced the highest degree of fast slow transformation. These findings support the view that denervation and dysthyreosis alter gene expression in muscle by independent mechanisms.     

Neuronal mechanisms for pitch analysis in the time domain

Summary Many units in the auditory midbrain nucleus (MLD) of the Guinea fowl are found to be tuned to amplitude modulated tones (AM). For a given response maximum the relationship of the period _m of the modulation frequency f_m and the period _c of the carrier frequency f_c may be given by an empirical equation: m · _m + n · _c = 1 · ₁, where m, n and 1 are small integers typical for a unit. ₁ is a time constant of 0.4 ms. The temporal pattern of the neuronal response support these findings. The averages of spike trains oscillate with periods multiple to ₁. These oscillations are elicited by stimulus onsets and zero crossings of f_m and may be coupled strongly to f_m depending on f_c. Variation of f_m or f_c shifts the mean delay of the phase coupled activity proportional to m · _m and n · _c, respectively. These effects may be explained with activity phase coupled to f_c which coincides at the level of the recorded units with oscillations coupled to f_m. This is expressed by the above given periodicity equation. Psychophysical results with AM-stimuli indicate that the mechanisms described and the periodicity equation are adequate for the explanation of the analysis of periodicity pitch in humans. Hence the period corresponding to pitch is defined by m · _m + n · _c = 1 · ₁, where n and 1 are integers and ₁ = 0.4 ms. Plots of _p as a function of _c reveal steps at 0.4 ms intervals indicating that the neuronal time constant is the same in both species.Supported by the DFG, SFB 45     

Transient expression of myosin heavy chain MHCIα in rabbit muscle during fast-to-slow transition

The expression of an -cardiac-like myosin heavy chain, MHCI, was investigated at both the mRNA and protein levels in rabbit tibialis anterior muscle undergoing fast-to-slow transition by continuous chronic low-frequency stimulation (CLFS). According to sequence analyses of the PCR product, the MHCI isoform was found to be identical to the -cardiac MHC expressed in rabbit atrium. In muscles at different degrees of transformation, the upregulation of MHCI mRNA preceded that of the MHCI mRNA. At more advanced stages of the transformation, MHCI mRNA decayed while MHCI mRNA persisted at high levels. The expression of MHCI, therefore, was transitory. Studies at the protein level were based on immunoblotting using a monoclonal antibody (F88 12F8,1), characterized to be specific to MHCI in rabbit muscle. These studies revealed a similar relationship between initial increase and successive decline of the MHCI protein as seen at themRNA level. Immunohistochemistry of 30-day stimulated muscle revealed that up to 65% of the fibres expressed the MHCI isoform in combination with other adult MHC isoforms. The most frequent patterns of coexistence were MHCIIa+MHCI + MHCI (28%), MHCI+MHCI (18%), and MHCIIa + MHCI (11%). According to these combinations, the upregulation of MHCI may be assigned as an intermediate step in the transformation of existing fibres during theMHCIIa MHCI transition. A small fraction of fibres contained, in addition to the MHCI + MHCI and MHCIIa + MHCI combinations, developmental myosin, suggesting that MHCI was also expressed in regenerating fibres originating from satellite cell-derived myotubes.     

Effect of dehydroepiandrosterone on radioligand binding of [<Superscript>3</Superscript>H]-testosterone by androgen receptors in rat hypothalamus

Intramuscular injections of dehydroepiandrosterone in a dose of 0.7 mg/kg for 10 days significantly increased nuclear and cytoplasmic fractions of androgen receptors in the preoptic/ anterior hypothalamic area. Presumably, the effect of the neurosteroid is mediated by 5-reductase transformation of dehydroepiandrosterone into 5-dehydroepiandrosterone, which initiates the synthesis of androgen receptors.Translated from Byulleten Eksperimentalnoi Biologii i Meditsiny, Vol. 138, No. 10, pp. 435–438, October, 2004