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Biomedical subjects

K Schwartz

Publications and source records attributed to K Schwartz.

At least 289 records · Page 16Linked to original sources
PubMed1979

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.

Adaptation, Physiological↗
PubMed1979

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.

Animals↗
PubMed1979

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.

Actins↗
PubMed1979

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.

Antibody Specificity↗
PubMed1979

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.

Aging↗
PubMed1979

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.

Adult↗
PubMed1978

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.

Affinity Labels↗
PubMed1978

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.

Computers↗
PubMed1978

[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.

Actins↗
PubMed1977

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.

Adenosine Triphosphatases↗
PubMed1977

Preparation of specific immune sera against rabbit skeletal, pig and human cardiac heavy meromyosins.

Antibodies were produced in guinea-pigs against heavy-meromyosin (HMM) and tested by immunodiffusion and microcomplement fixation (MCF). A similar response was obtained for HMM extracted either from human and pig left ventricles, or from rabbit white skeletal muscles. For each muscle, the antisera cross-react quantitatively with the native intact myosin and are highly specific. Thus, this procedure permits the preparation of muscle type-specific anti myosin antibodies, by a simpler means than those previously published.

Animals↗
PubMed1976

A comparative study of skeletal and cardiac tropomyosins: subunits, thiol group content and biological activities.

The subunit composition, the thiol group content and the biological activities of cardiac tropomyosins (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 alpha and beta on the different electrophoresis systems used, with a beta:alpha ratio respectively of I:4.2, I:4.6, I:4.8. The alpha-TM components from sheep skeletal and pig and sheep cardiac muscles were more positively charged than the rabbit skeletal alpha-TM component, as shown in alkaline urea electrophoresis system. The alphaalpha and alphabeta 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 beta 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.

Actomyosin↗