The effect of chronic alcohol ingestion on the contractile proteins of the rat heart.

With increasing duration of alcohol consumption the amounts of total myofibrillar proteins in CFY rats decreased slightly, but significantly (from 63.3 +/- 5.7 mg X g wet muscle weight to 54.9 +/- 5.9 mg X g-1 after 12 weeks on alcohol). Similar slight changes could be observed in the case of sarcoplasmic proteins. No significant changes were observed in the composition of the myofibrillar proteins. The densitiometrically calculated percentage ratios of myosin/actin, myosin light chains (LC1/LC2) and troponin components remained the same in the alcoholic animals. The same distribution of native myosin isoenzymes was found in the ventricles of the alcoholic animals as in the controls. We found no electrophoretically detectable evidence that a change in the composition of the myofibrillar proteins is responsible for the decreased contractility of the rat heart following chronic alcohol ingestion.

The effect of 4-aminopyridine-induced increased neuromuscular activity on the metabolism of developing muscles in chick embryos.

Chick embryos were treated with 4-aminopyridine (4 X 100 micrograms) during a critical stage of muscle development, and the effect of enhanced neuromuscular activity upon energy metabolism was studied in two fast-twitch muscles and a slow-tonic muscle. In the slow-tonic muscles of treated embryos, the specific activities of creatine kinase (CK) and lactate dehydrogenase (LDH) were reduced by 11 and 21%, respectively, compared with control values, whereas the ratios of the CK-MB isoforms and the LDH-H subunits increased to 125 and 135% of the control values, respectively. No significant changes could be shown in the enzymatic pattern of fast muscles. These results indicate that a moderate increase in neuromuscular activity of the chick embryo primarily influences the metabolism of developing slow muscles, promoting the development of an enzyme profile characteristic of slow oxidative fibres.

Effect of weightlessness on the function of rat skeletal muscles on the biosatellite "Cosmos-1129".

Isometric tension of glycerinated fibrils of different skeletal muscles was studied in white rats carried in the biosatellite "Cosmos-1129" for 18.5 days. Expression and trends of the changes in contractile properties of muscle preparations depend on their functional specialization. The most sensitive reaction was displayed by the soleus muscle which consists predominantly of slow fibres.

Effect of weightlessness on myofibrillar proteins of rat skeletal muscles with different functions in experiment of biosatellite "Cosmos-1129".

The composition of contractile and regulatory proteins was studied in rat muscles with different functions. The rats were exposed to weightlessness for 18.5 days during a space journey in biosatellite Cosmos-1129. Under the effect of weightlessness the myosin light chain composition changed, the quantity of myosin LC-3 subunits increased in the soleus and extensor digitorum longus (EDL) while it decreased in the triceps and brachialis muscles. The experiments showed changes in the subunit composition of the TN-TM complex, too. The results obtained are in favour of a possible adequate transformation of fibril phenotypes of some (antigravitational) muscles under the effect of spaceflight.

Experimental studies on hypokinesis of skeletal muscle with different functions. VI.

In rabbits, the right hind limb was immobilized by means of plaster cast for 1, 2, 4 or 6 weeks and the activities of some metabolic enzymes: GOT, GPT, LDH, aldolase and acid phosphatase (in part of lysosomal origin), were examined in the slow m. soleus, and in the fast m. gastrocnemius. The former muscle is known to have mainly an oxidative, while the latter mainly a glycolytic type of metabolism. The activities of enzymes highly involved in the metabolism of the muscle diminished for a certain time during atrophy, then a relative rise occurred. Acid phosphatase activity likewise decreased after an initial relative increase. Reduction of enzymatic activities is explained by the activation of proteolytic enzymes, on the basis of measurements performed in these experiments and of results published by others. The decrease of enzymatic activity was more marked in the muscle which in normal state exhibits higher activity than in the other type of muscle studied. Thus, in the gastrocnemius a high rate of degradation of glycolytic enzymes was observed, while in the soleus degradation of oxidative enzymes prevailed. This phenomenon leads to the dedifferentiation of the muscle cell during immobilization.

Experimental investigations on the hypokinesis of skeletal muscles with different functions, V.

The composition of myofibrillar proteins was studied in the soleus and gastrocnemius muscles of rabbit hind limbs immobilized by plaster cast in experiments lasting 1--4 weeks. The amounts of actin, M protein and C protein increased relative to the normal composition. The ratio of the light chain peptides of the fast muscle myosin changed from 1 : 2 : 1 to 1 : 2 : 0.5 as a result of 4 weeks of disuse. The LC-1 : LC-2 ratio of slow myosin did not change considerably while the amount of fast LC-3 peptide, hardly detectable in soleus muscle, increased more than tenfold. The amount of tropomyosin decreased significantly in both muscles. The submolecular composition of troponin changed, mostly in the slow muscle; TN--C and TN--I decreased significantly, whereas there was an increase in the TN--T values. It is concluded that the phenotype of the structural proteins of muscles with different functions is de-differentiated by disuse, while the genetic functions of the muscle cells is reprogrammed to the synthesis of contractile proteins (e.g. myosin) characteristic of the other type of muscle.

Effect of plaster-cast immobilization on the contractile properties of rabbit skeletal muscles of various functions.

The effect of plaster-cast immobilization was studied on the ATP-Ca++-induced contraction of glycerinated muscle fibres on myofibrillar superprecipitation and on the ATPase activity of gastrocnemius and soleus muscles obtained from rabbit hind limb. Following 28 days of immobilization the ATP-Ca++-induced tension of glycerinated muscle fibres prepared from the gastrocnemius and soleus muscles decreased significantly. Decreases in superprecipitation and in myofibrillar ATPase activity were less significant. It seems reasonable to conclude that the changes in the physiological parameters of isolated muscle fibres have been due to the alterations in the myofibrillar proteins induced by reduced activity of the muscles.

Changes in the contractile proteins of skeletal muscles induced by steroid myopathy.

The effect of chronic dexamethasone treatment was investigated on the myofibriller proteins of slow (soleus) and fast (semimembranous) muscles. The relative quantities of actin, protein C and protein M increased, while the myosin, troponin inhibitor and calcium binding components showed a relative decrease in both muscle types. The amount of troponin regulatory component and alpha-actinin decreased only in the fast muscle, while tropomyosin decreased significantly in the slow muscle. The isoenzyme pattern of fast muscle myosin was altered as a consequence of decreased myosin (LC-3 subunit.

Changes in the aerobic and anaerobic metabolism of skeletal muscle subjected to plaster cast immobilization.

The effect of immobilization for different periods (7, 14, 28 and 42 days) on the aerobic and anaerobic metabolism of rabbit muscles with different functions was studied by measuring the total activity of LDH and MDH as well as the distribution of their isoenzymes. The results showed that on plaster casting the characteristic aerobic metabolism of m. soleus declined with a concomitant increase in glycolytic processes. In m. gastrocnemius the anaerobic metabolism of the muscle was relatively decreased on immobilization, but glycolysis remained the prevailing energy yielding process. On immobilization the metabolism of m. soleus and that of m. gastrocnemius approached each other. This may indicate a certain dedifferentiation of the muscle tissue.

Changes in the sarcoplasmic proteins of skeletal muscles induced by experimental steroid myopathy.

The protein content and the relative distribution of cell compartments was investigated after 14 days of dexamethasone treatment in rabbits. The cell fractions were further analysed by SDS-PAGE. It was found that the loss of myofibrillar fraction was greater than that of the sarcoplasmic one. The susceptibility of fast-twitch fibres to steroid myopathy was more marked compared to the slow fibres. The sarcoplasmic proteins showed the following changes: myoglobin and myokinase decreased, while alpha-GPDH and LDH increased in both muscle types. On the other hand, the alterations of TPI, PGK, PGI, PK, ADA, phosphorylase kinase and phosphorylase b, were opposite in the two types of muscle. The results are in agreement with observations of others indicating that glucocorticoid treatment causes a shift in the equilibrium of synthesis and degradation of myofibrillar and sarcoplasmic proteins. The different susceptibility of fast versus slow muscles to steroid myopathy could be due to the activity-dependent regulatory mechanism of metabolic pathways.

[Investigations on the distribution of serum LDH isoenzymes of patients with carcinoma laryngis (author's transl)]. / Veränderung der Verteilung von Serum-LDH-Isoenzymen bei Patienten mit Kehlkopfkarzinom.

The distribution of lactate dehydrogenase (LDH) isoenzymes in healthy blood donors and in patients suffering histological identified tumor (neoplasms) laryngis was investigated. The values of 110 healthy persons (controls) proved to be comparable with the average data described in literature. The LDH distribution pattern of 90 tumour affected persons showed significant differences comparing with controls. The alteration appears as absolute increase in LDH-1 (H4) isoenzyme parallel with progressive decrease in the hybrid enzyme rations containing M subunits (LDH-2, LDH-3, LDH-4), and the LDH-5 consisting of four M sununits was undetectable. The conclusions drawn from our investigations seem to be in agreement with Warburg's conception, supposing that in malignant tumours the aerob glycolysis increases. The determination of LDH isoenzyme distributions for diagnostic purposes in clinical practice is recommended.

Experimental investigations on hypokinesis of skeletal muscles with different functions VII. Ultrastructural observations.

Ultrastructural investigations were carried out parallel with biochemical measurements on the limb muscles of rabbits immobilized by putting in plaster. The cellular structure of normal and immobilized (1--6 weeks) m. soleus and m. gastrocnemius (red tonic and white tetanic, respectively) were compared. During immobilization significant changes occurred in the cellular structure of m. soleus, while little change was observed in the white fibres of m. gastrocnemius. The fibres of m. soleus decreased in diameter and fatty infiltration set in. The myofibrils decreased in amount and their structure was damaged and disorganized but did not disappear completely. Mitochondria showed little damage, like membraneous structures in general, in number. Loss of material seems to be by way of vesicles formed by the heavily invaginated plasma membrane and by the deflation of the numerous vesicles observed. The red fibres of m. gastrocnemius behaved like the fibres of m. soleus; in the white fibres some focal disorganization was observed near the Z line. The cystae of mitochondria and the SR appear to be dilated.

Degradation of myones as a consequence of disuse and denervation.

After denervation or immobilization in both slow and fast muscles of rabbits a rapid decrease in weight and protein content and a focal degeneration of cell ultrastructure were observed. As a consequence marked changes in the ratio of soluble to myofibrillar protein and in regulatory proteins of myofibrillar system occurred.