Myosin isoenzyme changes in several models of rat cardiac hypertrophy

We studied the effect of chronic mechanical overloading on the isoenzyme composition of rat cardiac myosin in several experimental models: aortic stenosis (AS), aortic incompetence (AI), aortocaval fistula (ACF), overload of the non-infarcted area after left coronary ligation (INF), and overload of the spontaneously hypertensive rats (SHR). Samples of the left and right ventricles were isolated from these hearts, and myosins were analyzed by electrophoresis in non-dissociating conditions. The myosin isoenzymes were called V1, V2, and V3 in order of decreasing mobility, according to the nomenclature of Hoh et al. Controls of the Wistar and Wistar Kyoto (WKY) strains were almost exclusively V1, A slow age-dependent shift toward V3 was observed in the left ventricles of adult Wistar rats, which at 30 weeks of age (body weight 600 g) contained approximately 15% of this form. In all models of cardiac hypertrophy, an isoenzymic redistribution was observed with a significant increase in V3. The level of V3 was statistically correlated with the degree of hypertrophy in the AS, (n = 11, r - 0.6, P less than 0.05), the AI (n = 14, 4 = 0.88, P less than 0.001), and the AS + AI(n = 14, 4 = 0.69, P less than 0.01) but not in the ACF (n = 16, r = 0.46). The isoenzymic changes could account for the decreases in both myosin ATPase activity and cardiac contractility described previously in our laboratory and by others. They also demonstrate that changes in myosin isoenzymes represent a general response of the rat heart, to chronic mechanical overloading.

Use of antibodies against dodecylsulfate-denatured heavy meromyosins to probe structural differences between muscular myosin isoenzymes

Heavy meromyosin, a tryptic myosin fragment, was purified from rabbit fast twitch muscles and rat cardiac ventricles. Both types of heavy meromyosin were denatured by sodium dodecylsulfate and used to immunize guinea-pigs after chromatography on Sephadex G-10 to remove excess dodecylsulfate. Micro-complement fixation analysis showed that the antisera were specific to a denatured configuration of heavy meromyosin and myosin, and hardly recognized the native proteins. Cross-reactions performed with both rabbit skeletal and rat cardiac antisera indicated that the antigenic structures of denatured myosins varied according both to species (man, rabbit, rat or mouse), and to muscle-type (red skeletal slow twitch, while skeletal fast twitch, cardiac atria or cardiac ventricles). Denatured heavy meromyosin chromatography on Sephadex G-200 in the presence of 0.1% sodium dodecylsulfate enabled separation of several polypeptides groups. Of these, a polypeptide of Mr 29000 was the most reactive and exhibited the same immunological specificities as the whole myosin molecule. The use of antibodies against denatured heavy meromyosin in conjunction with micro-complement fixation therefore provides a discriminant means, not only for estimating the structural relationship between several myosin isoenzymes, but also for localizing constant and variable regions in the heavy chains of these isoenzymes.

Experimental systolic and diastolic overloading in rats: total proteins turnover rate. Enzymatic and structural properties of myosin

The fractional turnover rate of the total cardiac proteins has been measured by using the continuous infusion technique with 3H lysine. It augments by a factor of 3 in systolic as well as in diastolic overloading, but in the former the peak was reached within the first week after operation and in the later the peak was not reached until the 14th day. The myosin structure and enzymatic properties have been studied in several huge hypertrophic hearts (around 100% hypertrophy). In this condition the burst size of myosin is normal, as well as its K+ ATPase, but there is a sharp decline in the Ca2+ ATPase activity. Moreover, antibodies against native or defolded heavy meromyosin exhibit, a vertical shift in microcomplement fixation when made to react with molecules extracted from hypertrophied hearts. The normal isozymic pattern of rat heart myosin, as shown in non dissociating electrophoresis, was reversed.

Myosin isoenzyme redistribution in chronic heart overload

Since the first observation by Spann et al., it has become clear that in cardiac hypertrophy induced by a mechanical overloading, the velocity of shortening of the cardiac muscle (Vmax) is reduced (see ref. 2 for review). Most authors agree that this mechanical alteration is accompanied by a decrease in the Ca2+-dependent ATPase activity of myosin (see ref. 3 for review). The molecular basis of such changes was unknown because the structural modifications of the myosin molecule were ill-defined. Nevertheless, it has recently been shown that, like skeletal muscle myosin, cardiac myosin is composed of several polymorphic forms, comparable to isoenzymes. In the skeletal muscle, new functional requirements can induce changes in both contractile activity and type of myosin isoenzyme synthesised. We now report that an increase in cardiac work produced by mechanical overloading in rats induces the preferential synthesis of a cardiac myosin isoenzyme characterised by specific immunological and electrophoretic properties and exhibiting a lower ATPase activity. This adaptive change could account for the reduced shortening speed of this hypertrophied cardiac muscle.

Contractile protein isozymes in muscle development: identification of an embryonic form of myosin heavy chain

The nature of the myosin heavy chain in embryonic muscle tissue, cultured muscle cells, and several adult muscles was investigated. After denaturation with sodium dodecyl sulfate, purified rat myosins were subjected to partial proteolytic cleavage or immunological analysis using microcomplement fixation. Three types of myosin heavy chains could be demonstrated by both approaches. Whereas adult muscles contain fast- or slow-type myosin heavy chains, embryonic tissue and cultured muscle cells harbor a distinct embryonic form. The existence of this distinct form further characterizes the isozymic transitions of contractile proteins during muscle development.

Induction of specific anti-actin antibodies and their measurement by ELISA technique

Using the ELISA technique we have been able to quantify antibodies directed against actin and to follow the kinetics of antibody production. Specific anti-actin antisera have been raised in rabbits by immunization with chemically modified white muscle rabbit actin. Two or three dinitrophenyl groups linked per actin molecule were sufficient to break natural tolerance, while linkage of three phosphorylcholine groups to actin was not.

Detection of antibodies specific to sodium dodecyl sulfate-treated proteins

Heavy meromyosin (HMM) denatured by sodium dodecyl sulfate (SDS) was injected into guinea pigs, either in the presence of 1 mg SDS/mg protein or after chromatography on Sephadex G-10 to remove detergent excess. Antigen-antibody interactions were analyzed by the microcomplement fixation technique. When HMM was injected in the presence of excess of SDS, the microcomplement fixation curves exhibited two maxima; one was specific to the random coil configuration of heavy meromyosin or myosin, and the other was common to several SDS-protein complexes. The latter peak disappeared when the excess SDS was removed from the immunogen by chromatography. Results showed the presence of antibodies directed either against SDS or against the non-specific SDS protein link.

The big rib sign: localization of basal pulmonary pathology in lateral projection utilizing differential magnification of the two hemithoraces

Basal pulmonary pathology which silhouettes the hemidiaphragm in lateral view may not be detectable in routine postero-anterior projection. In such cases, correct lateralization of pathology to the left or right hemithorax depends on accurate identification of the silhouetted left and right hemidiaphragm in lateral view. A prospective analysis of the sensitivity and accuracy of five techniques for identifying the left and right hemidiaphragms in more than 100 patients revealed that the most accurate method for lateralizing juxtadiaphragmatic pathology was the "big rib" sign, a technique based upon the relative difference in magnification between the left and right ribs. Techniques based upon the visceral gas bubble or upon obscuration of the anterior portion of the left hemidiaphragm by the heart proved less useful. Techniques based upon the position and configuration of the major fissures or upon higher and lower position of the two hemidiaphragms were ineffective.

[Role of tropomyosin in the sensitivity of (Na+ + K+) ATPase to ouabain]

EDTA treatment of isolated plasma membranes from MF2S cells increased 1,000 fold the sensitivity of (Na+ + K+) ATPase activity to ouabain. The original sensitivity of the enzyme to the drug is recovered after addition of tropomyosin together with Ca++ ions to the treated membranes.

Species-dependent immunological differences between various mammalian cardiac tropomyosins

Antisera were produced from guinea-pigs against purified pig or rat cardiac tropomyosins and antigen-antibody interactions were analyzed by the micro-complement fixation technique. Immunoadsorption with purified tropomyosins coupled with CN Br-activated Sepharose 4B enabled us to establish that these antisera were only specific to tropomyosin and not to other contractile proteins. Direct cross-reactions and competition experiments performed with both the above antisera indicated quantitative differences in the maximum amount of complement fixed by tropomyosins from various heterologous species (man, beef, pig, rabbit, rat and mouse). These data provide direct evidence that mammalian cardiac tropomyosin is species-specific.

[Biochemistry of myocardium taken at autopsy. Preliminary report]

The findings after biochemical analysis of heart muscle taken at autopsy are given in this preliminary communication. Human myosin is made up of two heavy sub-units and two light sub-units: it is similar to cardiac myosin found in other mammals, but is different in certain characteristics, particularly immunological ones. Tropomyosin is made up of two different sub-units. The normal human heart contains 1 mg of collagen and 130 microgram of desoxyribonucleic acid (DNA) per 100 mg of fresh tissue. The degree of cardiac hypertrophy correlates with the increase total DNA within the heart, and with the lowering of myofibrillary Ca2+ ATPase, the concentration in the collagen remaining unchanged providing there is no ischaemic heart disease. These techniques may be used to quantify several factors, such as the degree of sclerosis or the nuclear mass in ill-understood conditions such as the primary cardiomyopathies.

Fluorescent photoaffinity labeling: adenosine 3',5'-cyclic monophosphate receptor sites

An approach to the study of protein receptor sites in protein mixtures or supramolecular assemblies by using fluorescence spectroscopy is described. This approach, fluorescent photoaffinity labeling, combines the merits of photoaffinity labeling to attain site-directed reactivity with the probing power of fluorescent ligands. A fluorescent photoaffinity label for cyclic AMP receptor sites of cyclic AMP-dependent protein kinases was synthesized in both unlabeled and radioactive forms. The probe, 8-azido-1,N(6)-ethenoadenosine 3',5'-cyclic monophosphate, mimics cyclic AMP in its ability to stimulate the phosphotransferase activity of the protein kinases and strongly competes with cyclic AMP for its binding sites in all preparations so far tested. Photolysis, after equilibration of protein kinase and 8-azido-1,N(6)-ethenoadenosine 3',5'-cyclic monophosphate in the dark, effects binding of the intermediate nitrene irreversibly and specifically to the cyclic AMP sites with the development of fluorescence. Excess reagent and low molecular weight photolytic products are removable by dialysis. Studies of a crude beef heart preparation containing cyclic AMP-dependent protein kinase suggest that the cyclic AMP binding sites are hydrophobic in nature and strongly immobilize the adenine moiety of the cyclic nucleotide.

Modifying the pattern of prescribing multiple pairs of glasses

The New York City Medicaid program uses computerized monitoring techniques as part of its effort to control the quality and utilization of services. The system can identify certain aberrant patterns of practice. For optometric services, one such practice by some providers is the prescribing of separate distance and near eyeglasses in lieu of bifocals. Sending a notification letter to these providers succeeded in modifying the practice. Computerized monitoring and association roles for professionals are discussed.

Immunochemical evidence for the species-specificity of mammalian cardiac myosin and heavy meromyosin

Structural differences between various myosins were investigated by means of antibodies to heavy meromyosin, a tryptic subfragment of myosin. Heavy meromyosin was purified from rabbit white skeletal and from pig and human cardiac muscles by gel filtration, and antisera were produced in guinea pigs. Analyses, carried out with the quantitative micro-complement fixation technique, indicated that the antibodies were specific to heavy meromyosin and myosin and not to other contractile proteins. For each muscle type, the corresponding intact myosin reacted, and the degree of dixation was always lower than with heavy meromyosin (50 and 70% fixation respectively). This vertical shift was the same for the three muscle types, indicating that the heavy meromyosin represent corresponding fragments of the myosin molecule from one muscle to the other. Antisera to pig or human cardiac heavy meromyosin clearly distinguished antigens (heavy meromyosins, myosins, or crude extracts) from the ventricles of various heterologous species. Relative to pig, the immunological distances were 50 for the rabbit, 73 for the rat and greater than 100 for human and mice. Relative to human, these values were 20 for the rat, 60 for the rabbit, 72 for the pig. These data provide direct evidence that mammalian cardiac myosin is species-specific.