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L Gorza

Publications and source records attributed to L Gorza.

54 records · Page 3Linked to original sources
PubMed1988

Slow-to-fast transformation of denervated soleus muscles by chronic high-frequency stimulation in the rat.

1. Adult soleus muscles were denervated and stimulated directly for 2-130 days with 'fast' (short pulse trains at 100 Hz) or 'slow' (continuously at 10 Hz, or long pulse trains at 15 Hz) stimulus patterns. 2. At the end of the period of stimulation isometric twitches and tetani and isotonic shortening velocities were measured. Frozen cross-sections were later examined with antibodies against myosin heavy chains specific for adult fast, adult slow and fetal myosin. 3. Isometric twitch duration (twitch time-to-peak and half-relaxation time) decreased during intermittent 100 Hz stimulation to values that were almost as fast as in the normal extensor digitorum longus (EDL) (95 and 94% transformation). The major part of the decrease occurred between 2 and 21 days after the onset of stimulation, and was accompanied by post-tetanic potentiation of the twitch, 'sag' in tension during an unfused tetanus, lower twitch/tetanus ratio and marked shifts to the right (higher frequencies) of the tension-frequency curve of the muscle. In contrast, during 10 or 15 Hz stimulation the isometric twitch duration remained slow, the twitch continued to show post-tetanic depression and absence of 'sag', while the twitch/tetanus ratio increased. 4. Denervation per se led to a slight increase and, then, after about a month, to a moderate and gradual decrease in twitch duration. The twitch/tetanus ratio increased markedly and post-tetanic depression became less pronounced or disappeared. Muscle weight and particularly tetanic tension were markedly reduced and these reductions were to a large extent counteracted by electrical stimulation. 5. Implantation of sham electrodes had no effect on twitch duration of denervated or innervated control muscles, but reduced tetanic tension in the innervated control muscles. 6. Maximum isotonic shortening velocity of the whole muscle (mm/s) increased during intermittent 100 Hz stimulation to a value as fast as in the normal EDL (110% transformation). Since the muscle fibres also increased in length (35%) maximum intrinsic shortening velocity (fibre lengths/s) was only incompletely transformed (55%). The increase in Vmax occurred between 7 and 14 days after the onset of stimulation. 7. All the fibres stimulated intermittently at 100 Hz were strongly labelled with anti-fast myosin and more than 90% were in addition weakly labelled by anti-slow myosin. Weak and variable labelling with anti-fast myosin was first detected 7 days after the onset of stimulation. In contrast, essentially all the fibres stimulated at 10 or 15 Hz showed no binding of anti-fast but strong binding of anti-slow myosin.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1988

Nodal myosin distribution in the bovine heart during prenatal development: an immunohistochemical study.

A novel type of cardiac myosin heavy chain, immunologically related to the myosin isoforms expressed during skeletal muscle development, has recently been described in sinoatrial and atrioventricular nodal fibers of the adult bovine heart (Gorza et al, J Cell Biol 1986; 102:1758-1766). The tissue-specific expression of this myosin type has been utilized in the present study to investigate the differentiation of nodal fibers during cardiac development. In 4-6-week-old bovine embryos, reactivity for nodal myosin was observed in a cluster of cardiac fibers in the sinus venosus wall, corresponding to the sinoatrial node primordium and in a number of fibers localized in the left atrial wall, especially in proximity to vascular orifices, possibly corresponding to the postulated left-sided sinoatrial node. In contrast, reactivity for nodal myosin was not detected in the atrioventricular node until 12 weeks of gestation. Before this stage, fibers reactive for nodal myosin were also seen scattered in the left atrial wall and interatrial septum, raising the possibility that atrioventricular nodal fibers may derive from the left-sided sinoatrial node. Reactivity for nodal myosin was never seen in normal atrial and ventricular myocardium, nor in the ventricular conduction tissue, indicating that nodal myosin does not represent a primordial myosin form, but is rather a specific marker of a distinct muscle cell lineage.

Animals↗
PubMed1987

Myosin isoform expression in rat rhabdomyosarcoma induced by Moloney murine sarcoma virus.

Myosin isoform expression was analyzed in experimental rhabdomyosarcoma (RMS) using monoclonal antibodies (mAbs) and immunofluorescence techniques. Tumors induced by inoculating newborn rats with Moloney murine sarcoma virus (Mo-MSV) were examined 30-90 days after birth. Nine tumors and two lymph node metastases were studied by direct, indirect, and double immunofluorescence assays using a panel of five anti-myosin mAbs. The mAb BF-45 was specifically reactive with embryonic myosin heavy chain (MHC), mAb BF-34 was specific for a neonatal MHC epitope, mAb BF-B6 was directed against an epitope present in both embryonic and neonatal MHC, and mAbs BF-F3 and BF-32 detected epitopes present in adult MHC isoforms. Anti-desmin antibodies were also used for comparison. The results of this study show that: (1) the majority of neoplastic cells stained for desmin while only a minority of neoplastic cells were labeled by anti-myosin antibodies; (2) myosin positive tumor cells contained predominantly embryonic and neonatal MHC types but rare RMS cells reacted exclusively with anti-adult myosin antibodies; and (3) adult and embryonic MHC phenotypes were occasionally detected within the same tumor cell especially in RMS with the longest latencies. Together these results would suggest that the mechanism(s) regulating MHC gene expression in skeletal muscle cells can be altered by the transforming activity of Mo-MSV.

Animals↗
PubMed1987

Fibre types in extraocular muscles: a new myosin isoform in the fast fibres.

We report on the existence of a myosin heavy chain (MHC) isoform with unique structural properties in extraocular (EO) muscles. Differences in MHC composition are apparent using a polyclonal antibody prepared against myosin isolated from bovine EO muscle myosin. In enzyme immunoassays and western blotting experiments, this anti-EO myosin antibody reacted specifically with the heavy chains of EO muscle myosin and not with the heavy chains of other myosins. The distribution of this new MHC isoform in the globe rotating muscles from different mammalian species was analysed using a panel of specific anti-myosin antibodies and comparing the histochemical myosin ATPase profile of muscle fibres with their isomyosin content. Most fibres which display a type 2 ATPase reaction pattern were selectively labelled by anti-EO antibodies. A few type 2 fibres were found to react with both anti-EO and anti-2A myosin antibodies and others, located almost exclusively in the orbital layers, reacted with anti-foetals as well as anti-EO antibodies. The presence of a distinct form of myosin in EO muscle fibres is probably related to the particular functional characteristics of these muscles, which are known to be exceptionally fast-contracting but display a very low tension output.

Animals↗
PubMed1986

Fetal myosin immunoreactivity in human dystrophic muscle.

We report immunofluorescence observations on normal and dystrophic human muscle using an antibody (anti-bF) raised against bovine fetal myosin and specific for fetal myosin heavy chains. In rat skeletal muscle, anti-bF was previously found to react selectively with myosin isoforms expressed during fetal and early postnatal development and in regenerating muscles. Anti-bF stained most fibers in human fetal and neonatal muscle, whereas only nuclear chain fibers of muscle spindles were labeled in normal adult muscle. In muscle biopsies from patients with Duchenne's muscular dystrophy, numerous extrafusal fibers were stained: some were small regenerating fibers, others were larger fibers presumably resulting from previous regenerative events. Fetal myosin immunoreactivity in Duchenne's dystrophy appears to reflect the reexpression of fetal-specific myosin isoforms and provides a new valuable tool for identifying regenerating fibers and following their destiny in dystrophic muscle.

Adolescent↗
PubMed1986

Embryonic myosin heavy chain as a differentiation marker of developing human skeletal muscle and rhabdomyosarcoma. A monoclonal antibody study.

Hybridoma cell lines were obtained from the fusion of NS-O myeloma cells with spleen cells of mice immunized with bovine fetal skeletal myosin. A stable hybridoma clone, BF-G6, produced immunoglobulin G1 k antibodies reacting specifically with embryonic-type myosin heavy chains present in fetal but not in neonatal or adult human skeletal muscle, as determined by enzyme immunoassay and immunoblot analysis. Fetal but not adult skeletal muscle fibers were stained by this monoclonal antibody in indirect immunofluorescence assays; smooth muscle cells and cardiac muscle cells, as well as non-muscle cells were also unreactive. Solid tumors of infants and children were tested for reactivity with BF-G6 by immunofluorescence and immunoperoxidase staining. Embryonic myosin heavy chain was expressed in rhabdomyosarcomas but not in other types of tumor, except for Wilms' tumor. Rhabdomyosarcoma cells isolated from a bone marrow metastasis and grown in vitro for several months were also labelled by BF-G6. Embryonic myosin heavy chain can thus be used as a specific differentiation marker of normal and neoplastic skeletal muscle tissue.

Adolescent↗
PubMed1986

Myosin types and fiber types in cardiac muscle. III. Nodal conduction tissue.

The sinoatrial (SA) and atrioventricular (AV) nodes are specialized centers of the heart conduction system and are composed of muscle cells with distinctive morphological and electrophysiological properties. We report here results of immunofluorescence and immunoperoxidase studies on the bovine heart showing that a large number of SA and AV nodal cells share a distinct type of myosin heavy chain (MHC) which is not found in other myocardial cells and can thus be used as a cell-type-specific marker. The antibody used in this study was raised against fetal skeletal myosin and reacted with fetal skeletal but not with adult skeletal MHCs. Both atrial and ventricular fibers, as well as fibers of the ventricular conduction tissue were unlabeled by this antibody. Specific reactivity was exclusively seen in most cells in the central portions of the SA and AV nodes and rare cells in perinodal areas. However, a number of nodal cells, particularly those located in the peripheral nodal regions, were unreactive with this antibody. The myosin composition of nodal tissues was also explored using two antibodies reacting specifically with alpha-MHC, the predominant atrial isoform, and beta-MHC, the predominant ventricular isoform. Most nodal cells were reactive for alpha-MHC and a number of them also for beta-MHC. Variation in reactivity with the two antibodies was also observed in perinodal areas: at these sites a population of large fibers reacted exclusively for beta-MHC. These findings point to the existence of muscle cell heterogeneity with respect to myosin composition both in nodal and perinodal tissues.

Animals↗
PubMed1986

[Cardiac myosins and myocardial contraction].

The contractile properties of cardiac muscle cells are determined by the molecular composition of the contractile apparatus and in particular by the structure of myosin. Three isoforms of myosin heavy chains have been recently identified in the mammalian heart: alpha and beta myosin heavy chains, present in atrial and ventricular myocardium, and nodal myosin heavy chain, present in sino-atrial and atrio-ventricular nodes. The alpha and beta isoforms are coded by two distinct genes whose expression is tissue and developmental stage-specific, and can be regulated by hormonal and mechanical factors. The relative concentration of the two isoforms is correlated with the maximal velocity of shortening and with the energy cost of force generation. In hyperthyroid myocardium the predominant isoform is the alpha, high ATPase myosin heavy chain and the contraction is fast but less economical; in hypothyroid and in mechanically overloaded myocardium the beta, low ATPase isoform is predominant and the contraction is slower and more economical.

Adenosine Triphosphatases↗
PubMed1986

Immunocytochemistry of rhabdomyosarcoma. The use of four different markers.

Fast myosin and slow myosin are specific markers of skeletal muscle, in addition to myoglobin. This study of 15 specimens of rhabdomyosarcomas from 13 patients using specific antisera for the three markers as well as for desmin led to positive findings in all cases with at least one antiserum. Desmin was present in all cases; fast myosin and myoglobin were present in 10 cases each. Slow myosin was present in six cases. It appears that the combination of several markers is helpful in differentiating rhabdomyosarcomas from other tumors. The markers considered were generally more abundant in neoplastic elements with large amounts of cytoplasm. This finding suggests that the larger cells of rhabdomyosarcomas are more differentiated than smaller rhabdomyoblasts, which were often negative with some of the antisera used.

Adolescent↗
PubMed1984

Myosin changes in hypertrophied human atrial and ventricular myocardium. A correlated immunofluorescence and quantitative immunochemical study on serial cryosections.

Two antigenically distinct types of myosin heavy chain, referred to as alpha and beta, have been identified in autoptic and bioptic specimens of human heart using specific antimyosin antibodies. By immunofluorescence heavy chain alpha was present in all atrial myocytes and in a variable number of ventricular myocytes. Heavy chain beta was present in all ventricular myocytes and in a number of atrial myocytes. Ventricular hypertrophy in patients with aortic stenosis, systemic hypertension or tetralogy of Fallot was characterized by an almost complete absence of fibres reactive with anti-alpha. A striking decrease in alpha chain reactivity and a parallel increase in beta chain reactivity was apparent in the hypertrophied left atria of patients with mitral stenosis. To quantify these myosin changes a novel procedure was developed whereby myosin was extracted from single cryosections serial to those processed for immunofluorescence and the relative amount of alpha and beta heavy chain was determined by enzyme immunoassay. Heavy chain alpha was less than 5% in most normal ventricular specimens and disappeared completely under the effect of pressure overload. On the other hand heavy chain beta was generally undetectable in the left atrial myocardium but increased up to 90% in biopsies of hypertrophied atria.

Adult↗
PubMed1984

Myosin types in the human heart. An immunofluorescence study of normal and hypertrophied atrial and ventricular myocardium.

Two distinct myosin heavy chain isoforms, referred to as alpha and beta, were identified in the human heart with specific antimyosin antibodies. By indirect immunofluorescence, myosin heavy chain alpha was found to be a major component of atrial myosin and a minor component of ventricular myosin, while heavy chain beta was found to be a major component of ventricular myosin and a minor component of atrial myosin. In the normal heart, there was marked individual variability in the proportion of ventricular myocytes reactive for heavy chain alpha. Atrial myocytes staining for heavy chain beta were rare in the left atrium and more numerous in the right atrium, especially in the crista terminalis and in the interatrial septum. Surgical and autoptic specimens from hypertrophied left ventricles of patients with mitral regurgitation showed a myosin immunoreactivity pattern similar to that of normal specimens. Very rare muscle cells reactive for heavy chain alpha were seen in the hypertrophied left ventricles of subjects with hypertension and in the hypertrophied right ventricles of subjects with tetralogy of Fallot. A dramatic transformation of myosin heavy chain composition was observed in hypertrophied left atria of patients with mitral stenosis, with a shift to heavy chain beta in a large proportion of atrial myocytes. The findings indicate that chronic exposure to hemodynamic overload can induce marked changes in the myosin heavy chain composition of human atria, whereas it affects only slightly that of the ventricles.

Adult↗
PubMed1983

Myosin isoenzymes in normal and hypertrophied human ventricular myocardium.

We tested the hypothesis that hypertrophy of the human heart is associated with the redistribution of ventricular isomyosins. Human cardiac myosin was isolated from autopsy samples of left ventricular free wall of patients with cardiac hypertrophy and of fetal, young, and adult subjects without heart disease. The following parameters were studied: electrophoretic migration in denaturing and non-denaturing conditions; immunological cross-reactivities with three different types of antibodies; and early phosphate burst size and steady state ATPase activities stimulated by K+-EDTA, Ca++, Mg++, and actin. The antibodies were chosen for their ability to recognize selectively the rat V1 and V3 cardiac isomyosins. The first type was a monoclonal antibody, CCM-52, prepared against embryonic chick cardiac myosin, the second was an anti-beef atrial myosin, and the third was an anti-rat V1 myosin. CCM-52 reacted with a greater affinity with rat V3 than with rat V1, and was a probe of mammalian V3. Anti-beef atrial myosin and anti-rat V1 myosin both recognized specifically beef atrial and rat V1 myosins, and were thus considered as probes of mammalian V1. Under non-denaturing conditions, human myosins migrated as rat V3 isomyosin; under denaturing conditions, no difference was observed in any of the electrophoretic parameters between all samples tested, except for the fetal hearts which contained a fetal type of light chain. The immunological studies indicated that human myosins were composed mostly of a V3 type (HV3), but contained also some V1 isomyosin. A technique was developed to quantify the amount of human VI isomyosin which was found to range from almost 0 to 15% of total myosin, and to vary from one heart to the other, regardless of the origin of the heart. Enzymatic studies showed no significant difference between normal, hypertrophied, and fetal hearts in any of the activities tested. However, there was a significant correlation between Ca++-stimulated ATPase activities and HV1 amount (at 0.05 M KCl, n = 18, r2 equal 0.49, P less than 0.01; at 0.5 M KCl, n = 18, r 2 = 0.5, P less than 0.01). These data demonstrate the heterogeneity of human ventricular myosin, which appears to be composed, as in other mammalian species, of V1 and V3 isoforms of different ATPase activities (V1 greater than V3). However it seems that V1 to V3 shifts do not appear to be of physiological significance in the adaptation of human heart to chronic mechanical overloads.

Actins↗
PubMed1982

Fetal myosin heavy chains in regenerating muscle.

There are several lines of evidence for the existence of a distinct class of myosins in developing muscle. Using various biochemical and immunological approaches, Whalen et al. recently suggested that two myosin heavy chain isozymes appear sequentially in rat muscle development, preceding the definitive adult myosins. It is unknown whether these myosins are present only in developing fast muscles or whether they also occur in developing slow muscles. Pyrophosphate of gel electrophoresis studies have suggested that fast-twitch and slow-twitch muscles synthesize the same fetal myosin isozymes early in development. Immunocytochemical studies with antibodies directed against adult fast and slow myosins show differences in myosin composition between fetal muscle fibres but interpretation of these findings is complicated by cross-reactions of these antibodies with fetal isomyosins. We have used a more direct immunocytochemical approach to identify the myosin types present in developing muscle fibres. An antibody specific for bovine fetal myosin and cross-reactive with rat fetal myosin has been prepared. We report here that the fetal myosin heavy chains recognized by this antibody show a heterogeneous fibre distribution in fetal and neonatal rat muscle, disappear progressively during postnatal development and are transiently expressed in regenerating muscle.

Animals↗
PubMed1982

Myosin types and fiber types in cardiac muscle. II. Atrial myocardium.

Antibodies were produced against myosins isolated from the left atrial myocardium (anti-bAm) and the left ventricular myocardium (anti-bVm) of the bovine heart. Cross-reactive antibodies were removed by cross-absorption. Absorbed anti-bAm and anti-bVm were specific for the myosin heavy chains when tested by enzyme immunoassay combined with SDS gel electrophoresis. Indirect immunofluorescence was used to determine the reactivity of atrial muscle fibers to the two antibodies. Three populations of atrial muscle fibers were distinguished in the bovine heart: (a) fibers reactive with anti-bAm and unreactive with anti-bVm, like most fibers in the left atrium; (b) fibers reactive with both antibodies, especially numerous in the right atrium; (c) fibers reactive with anti-bVm and unreactive with anti-bAm, present only in the interatrial septum and in specific regions of the right atrium, such as the crista terminalis. These findings can be accounted for by postulating the existence of two distinct types of atrial myosin heavy chains, one of which is antigenically related to ventricular myosin. The tendency for fibers labeled by anti-bVm to occur frequently in bundles and their preferential distribution in the crista terminalis, namely along one of the main conduction pathways between the sinus node and the atrioventricular node, and in the interatrial septum, where different internodal tracts are known to converge, suggests that these fibers may be specialized for faster conduction.

Adenosine Triphosphatases↗
PubMed1981

Myosin types and fiber types in cardiac muscle. I. Ventricular myocardium.

Antisera against bovine atrial myosin were raised in rabbits, purified by affinity chromatography, and absorbed with insolubilized ventricular myosin. Specific anti-bovine atrial myosin (anti-bAm) antibodies reacted selectively with atrial myosin heavy chains, as determined by enzyme immunoassay combined with SDS-gel electrophoresis. In direct and indirect immunofluorescence assay, anti-bAm was found to stain all atrial muscle fibers and a minor proportion of ventricular muscle fibers in the right ventricle of the bovine heart. In contrast, almost all muscle fibers in the left ventricle were unreactive. Purkinje fibers showed variable reactivity. In the rabbit heart, all atrial muscle fibers were stained by anti-bAm, whereas ventricular fibers showed a variable response in both the right and left ventricle, with a tendency for reactive fibers to be more numerous in the right ventricle and in subepicardial regions. Diversification of fiber types with respect to anti-bAm reactivity was found to occur during late stages of postnatal development in the rabbit heart and to be influenced by thyroid hormone. All ventricular muscle fibers became strongly reactive after thyroxine treatment, whereas they became unreactive or poorly reactive after propylthiouracil treatment. These findings are consistent with the existence of different ventricular isomyosins whose relative proportions can vary according to the thyroid state. Variations in ventricular isomyosin composition can account for the changes in myosin Ca2+-activated ATPase activity previously observed in cardiac muscle from hyper- and hypothyroid animals and may be responsible for the changes in the velocity of contraction of ventricular myocardium that occur under these conditions. The differential distribution of ventricular isomyosins in the normal heart suggests that fiber types with different contractile properties may coexist in the ventricular myocardium.

Animals↗
PubMed1981

Isomyosin distribution in normal and pressure-overloaded rat ventricular myocardium. An immunohistochemical study.

We have used affinity-purified antibodies reacting with guinea pig soleus muscle and ventricular myosin heavy chains to analyze the distribution of specific isomyosin in the ventricular myocardium of normal and renal hypertensive rats. Immunofluorescent staining of cardiac tissue sections with the two antimyosins revealed striking variations in reactivity among ventricular muscle fibers, reactive fibers being more numerous in the left compared to the right ventricle and in subendocardial compared to subepicardial layers. The response of the ventricular myocardium changed during development: all fibers were stained in the newborn rat, whereas most fibers were unreactive in 1-month-old animals. The number of reactive fibers increased again in subsequent stages leading to a mixed pattern in adult animals. The normal mixed pattern of reactivity was transformed into a uniformly positive pattern in hypertensive rats 2 months after surgery. This complete transformation was observed in 20 out of 23 hypertensive animals examined. These findings indicate that the two antimyosins cross-react with a particular type of ventricular myosin heavy chain, whose distribution varies in different muscle cells and whose relative concentration changes during development and during cardiac hypertrophy induced by systemic hypertension. We suggest that differences in pressure load may be responsible for both regional variations in isomyosin distribution and for isomyosin changes in hypertensive animals.

Animals↗