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Biomedical subjects

J F Hoh

Publications and source records attributed to J F Hoh.

At least 37 records · Page 2Linked to original sources
PubMed1990

Localization of human cardiac beta-myosin heavy chain gene (MYH7) to chromosome 14q12 by in situ hybridization.

The genes coding for each human cardiac myosin heavy chain (alpha-MHC and beta-MHC, MYH6 and MYH7, respectively) are tightly linked and the alpha-MHC gene has been assigned to chromosome 14. In order to provide a more precise regional localization, in situ hybridization experiments were carried out using a 3H-labeled probe derived from a beta-MHC genomic clone. The results demonstrated that the human cardiac MHC genes are located within the q12 band of chromosome 14.

Chromosome Banding↗
PubMed1989

Immunocytochemical analysis of the perinatal development of cat masseter muscle using anti-myosin antibodies.

The developmental changes in myosin gene expression in the masseter muscle of embryonic and juvenile kittens were examined immunocytochemically using anti-myosin heavy chain antibodies of various specificities. In the mature cat, this muscle contains only two phenotypes, the majority of fibres are superfast, the rest being slow fibres. In foetal tissues, the histological appearance of bundles of myotubes, comprising a large central myotube surrounded by a rosette of smaller myotubes, strongly suggest the existence in the jaw muscle of primary and secondary fibres during development. Immunocytochemical data are consistent with the hypothesis that there are four types of fibre; two types of primary fibre as well as two types of secondary fibre. (1) Slow primaries stain strongly with an anti-slow myosin antibody throughout the period under study. These fibres transiently express embryonic but not foetal myosin. (2) Superfast primaries stain for embryonic/foetal and slow myosins in the perinatal period but progressively replace these myosins with superfast myosin during postnatal development. (3) Superfast secondaries initially express embryonic/foetal myosins, but later, beginning around the time of birth progressively replace these myosins with superfast myosin. These fibres do not express slow myosin. (4) Slow secondaries, which initially also express embryonic/foetal myosins, but which postnatally express slow or slow and superfast myosins and express only slow myosin in the adult. These four types of fibres are homologous to the four isotypes of limb muscle fibres and may be derived from distinct lineages of myoblasts.

Animals↗
PubMed1989

Regeneration of cat posterior temporalis muscle in culture.

Cat posterior temporalis muscle has a rapid speed of contraction associated with a unique superfast myosin isoform. Superfast myosin expression appears to be an intrinsic property of the muscle fibres and satellite cells, though in culture they failed to express superfast myosin. We have, therefore, cultured this muscle in a system which had previously been shown to encourage the expression of an adult phenotype. The presence of nerve cells resulted in effective regeneration of cat posterior temporalis muscle and even the formation of functional neuromuscular junctions. However, superfast myosin was not found even in mature, contracting, innervated cultures. Thyroid hormone, a known regulator of myosin isoform expression, also failed to elicit superfast myosin expression. Different culture conditions may allow a different outcome, but under circumstances in which mouse muscle expresses an adult phenotype, cat posterior temporalis muscle fails to do so.

Animals↗
PubMed1988

Immunocytochemical and electrophoretic analyses of changes in myosin gene expression in cat limb fast and slow muscles during postnatal development.

Changes in myosin synthesis during the postnatal development of the fast extensor digitorum longus (EDL) and the slow soleus muscles of the kitten were examined using immunocytochemical techniques supplemented by pyrophosphate gel electrophoresis and gel electrophoresis-derived enzyme linked immunosorbent assay (GEDELISA) of myosin isoforms. The antibodies used were monoclonals against heavy chains of slow and fast myosins and a polyclonal against foetal/embryonic myosin. In both muscles in the newborn kitten, there was a population of more mature fibres which stained strongly for slow but weakly for foetal/embryonic myosin. These fibres were considered to be primary fibres. They formed 4.8% of EDL fibres and 26% of soleus fibres at birth, and continued to express slow myosin in adult muscles. The less mature secondary fibres stained strongly for foetal/embryonic myosin, and these could be divided into two subpopulations; fast secondaries in which foetal/embryonic myosin was replaced by fast myosin, and slow secondaries in which the myosin was replaced by slow myosin. At 50 days the EDL had a large population of fast secondaries (83% of total fibres) and a small population of slow secondaries which gradually transformed into fast fibres with maturity. The vast majority of secondary fibres in the soleus were slow secondaries, in which slow myosin synthesis persisted in adult life. There was a restricted zone of fast secondaries in the soleus, and these gradually transformed into slow fibres in adult life. It is proposed that the emergence of primary fibres and the two populations of secondary fibres is myogenically determined.

Animals↗
PubMed1988

Immunocytochemical and electrophoretic analyses of changes in myosin gene expression in cat posterior temporalis muscle during postnatal development.

Changes in myosin gene expression during the postnatal development of the homogeneously superfast kitten posterior temporalis muscle were examined using immunocytochemical techniques supplemented by pyrophosphate gel electrophoresis and gel electrophoresis-derived enzyme linked immunosorbent assay (GEDELISA) of myosin isoforms. The antibodies used were polyclonals directed against the heavy chains of superfast and foetal myosins and monoclonals against the heavy chains of slow and fast myosins. The fibres of the posterior temporalis in the newborn kitten stained almost uniformly with the anti-foetal myosin antibody and the largest of these fibres stained strongly for superfast myosin. A subpopulation of fibres staining for superfast myosin also stained lightly for slow myosin. These slow staining fibres were evenly distributed in the centres of muscle fibre bundles, reminiscent of primary fibres in limb fast muscle. During subsequent development, slow myosin staining disappeared and superfast myosin replaced foetal myosin so that by 50 days the muscle was virtually homogeneously superfast as in the adult. Fast myosin was never expressed at any stage. It is proposed that fibres staining transiently for slow myosin are superfast primary fibres which are homologous to fast primary fibres recently described in regions of limb muscles devoid of slow fibres in the matured animal. Other jaw-closing muscles have significant populations of slow fibres in the mature animal and it is postulated that there exists in these muscles a second class of jaw primary fibres, the slow primary fibres, in which slow myosin synthesis would be sustained in the adult. It is suggested that the myogenic cells of jaw-closing and limb muscles are of two distinct types preprogrammed to express different muscle genes.

Animals↗
PubMed1988

Myogenic and neurogenic regulation of myosin gene expression in cat jaw-closing muscles regenerating in fast and slow limb muscle beds.

Immunocytochemical techniques were used to study changes in myosin gene expression during the regeneration of the cat posterior temporalis muscle transplanted into the bed of either the fast extensor digitorum longus (EDL) or the slow soleus muscle. Strips of the posterior temporalis, a homogeneously superfast muscle, were treated with Marcaine and then transplanted into limb muscle beds which had been completely cleared of host muscle fibres. The regenerates were examined 6 to 224 days after surgery. Early regenerates in both muscle beds reacted with antibodies against the heavy chain of foetal, slow and superfast myosins, but not with antibodies against fast myosin. In the long-term, regenerates innervated by the EDL nerve expressed only superfast myosin whereas in the regenerates innervated by the soleus nerve most fibres expressed only slow myosin and only a few fibres reacted exclusively with the anti-superfast myosin antibody even after 210 days. In contrast, EDL and soleus muscles regenerating in their own beds expressed foetal, slow and fast myosin, but did not express superfast myosin. The isometric contraction times of the various types of regenerates reflected the types of myosin synthesized. It is concluded that jaw and limb muscle cells exist as two distinct allotypes, each having a distinct repertoire for the expression of adult isomyosins, and that within that repertoire isomyosin gene expression can be modulated by the nerve. Thus, myosin gene expression in skeletal muscle fibres is regulated by both myogenic and neurogenic mechanisms.

Animals↗
PubMed1988

Adrenaline increases the rate of cycling of crossbridges in rat cardiac muscle as measured by pseudo-random binary noise-modulated perturbation analysis.

The mechanism of action of adrenaline on cardiac contractility in rat papillary muscles containing V1 and V3 isomyosins was analyzed during barium-activated contractures at 25 degrees C by frequency domain analysis using pseudo-random binary noise-modulated perturbations. The analysis characterizes a frequency (fmin) at which dynamic stiffness of a muscle is a minimum, a parameter that reflects the rate of cycling of crossbridges. We have previously shown that fmin for V1- and V3-containing papillary muscles were 2.1 +/- 0.2 Hz (mean +/- SD) (n = 10) and 1.1 +/- 0.2 Hz (n = 8), respectively, and that these values were independent of the level of activation. The present study's goal was to determine whether the inotropic action of adrenaline was associated with an increased rate of crossbridge cycling. The results show that a saturating dose of adrenaline increased fmin in V1 hearts by 49 +/- 2% (n = 11). The action on V3 hearts was significantly less; the increase in fmin was 26 +/- 2% (n = 6). The increase in fmin for V1 hearts was shown to be sensitive to the beta-blocking agent propranolol. These results suggest that adrenaline significantly increases the rate of crossbridge cycling by a beta-receptor-mediated mechanism. We conclude that the increased contractility of the heart in the presence of adrenaline arises not only from more complete activation of the contractile proteins but also from the increased rate at which each crossbridge can transduce energy.

Animals↗
PubMed1986

Influence of V1 and V3 isomyosins on the mechanical behaviour of rat papillary muscle as studied by pseudo-random binary noise modulated length perturbations.

Experiments were done on four-week-old rats, containing biochemically verified V1 only, and thyroidectomized adult rats, treated with propylthiouracil, verified to contain V3 only. Contracture tension was induced in isolated papillary muscles either by high potassium solution or 0.5 mmol l-1 Ba2+. Small amplitude length perturbations with peak-to-peak value not exceeding 0.15% L0 were applied to the activated muscle. Both the applied length perturbations and the corresponding resulting force changes were analysed by computer for dynamic stiffness and phase values. In order to reduce data acquisition time, pseudo-random binary noise length changes, rather than the conventional sinusoidal length changes, were used. The plot of the dynamic stiffness against frequency displays a minimum, akin to a resonance phenomenon. The frequency, fmin, at which this resonance occurs, reflects crossbridge kinetics. It was found that the fmin values for the two types of papillary muscles differed by a factor of two. Experiments were also done on chemically skinned muscles containing V1 or V3 isomyosin activated by different concentrations of either barium or calcium ions. It was found that fmin values of skinned fibres were higher than those obtained from intact fibres. However, for each type of muscle the fmin was independent of the activator used as well as the level of activation. The ratio of fmin for V3 to that for V1 remained the same as for intact preparations. We conclude that the difference in mechanical parameters did not arise a possible difference in excitation-contraction coupling mechanism, but rather is a difference in the dynamic properties of the two types of crossbridges.

Animals↗
PubMed1984

Myosin isoenzymes in single muscle fibres of Xenopus laevis: analysis of five different functional types.

An analysis has been performed of the native myosin isoenzyme composition of isolated skeletal muscle fibres from Xenopus laevis with well-defined isotonic contraction properties. Fast twitch 'white' (type 1) fibres contained three isomyosins; fast twitch 'red' (type 2) fibres showed two major myosin bands with migration velocities very similar to those of the two slower bands in type 1. Slow twitch (type 3) fibres yielded a single, slowly migrating band as did slow tonic (type 5) fibres, whereas the myosin from type 4 (very slow twitch, 'intermediate') fibres migrated with a somewhat higher mobility. The results suggest that amphibian skeletal muscle may possess the principal fibre types found in mammals and birds.

Adenosine Triphosphatases↗
PubMed1983

Myosin isoenzymes in fast-twitch and slow-twitch muscles of normal and dystrophic mice.

An analysis of the native myosin isoenzyme composition, myosin light-chain distribution and histochemical profile of fast-twitch and slow-twitch muscles of normal and dystrophic (129 REJ dy/dy) mice has been performed, and the results correlated with the known contractile abnormalities of murine dystrophic muscles. Normal mouse slow-twitch soleus contained two isomyosins (slow myosin, SM and intermediate myosin, IM) which were electrophoretically distinct from the three major isomyosins (FM1, FM2, FM3) of fast-twitch extensor digitorum longus (e.d.l.) muscle. The calcium-activated ATPase activities of FM1, FM2, FM3 and IM at pH 9.2 were each much higher than that of SM, and this difference is reflected in the histochemical profile of muscle, as demonstrated with the myofibrillar ATPase reaction at alkaline pH. E.d.l. Type II fibres retained myofibrillar ATPase activity following pre-incubation of histochemical sections at pH 4.6, and were therefore classified Type IIB, whereas soleus Type II fibres did not, and were classified Type IIA. It was concluded that Type I (slow) fibres contain SM, Type IIA (intermediate) fibres contain IM, and Type IIB (fast) fibres contain FM1-FM3. Each electrophoretically distinct myosin contained a different combination of the five skeletal myosin light chains (LCs). Thus different normal muscles, which differed in their isomyosin profiles, differed also in their light-chain composition. Analysis of the distribution of native myosins (FM1, FM2, FM3, IM, SM, in order of decreasing gel migration rate) in dystrophic muscles revealed increased proportions of the slower-migrating forms, when compared with the distribution in the corresponding normal muscles. The shift in isomyosin distribution would explain the known decrease in the proportion of myosin light chain (LCf3) in murine dystrophic muscle. The abnormal isomyosin distribution in the dystrophic muscle is correlated with its altered histochemical characteristics, and with well-established abnormalities in its isometric and isotonic properties. It is concluded that the altered isomyosin distribution in murine dystrophic muscle would result in decreased power output per unit muscle mass when compared with normal muscle. The possibility is considered that defective myelination of the innervating nerve may contribute to these abnormalities by preventing higher frequency impulses from reaching muscle.

Animals↗
PubMed1982

Energetic consequences of thyroid-modulated shifts in ventricular isomyosin distribution in the rat.

Heat production (measured myothermically), force development and isomyosin distribution were measured in left ventricular papillary muscles from adult male rats in three thyroid states: hyperthyroid (T3), euthyroid (C) and hypothyroid (Tx). Rats were rendered hyperthyroid by daily injections of tri-iodothyronine and hypothyroid by radioisotopic thyroidectomy. Papillary muscle performance was measured both for trains of isometric twitches and for brief (2 s) tetani achieved by increasing the Ca2+ concentration and adding caffeine to the bathing solution. Resting metabolic rate was uninfluenced by thyroid state. Heat-stress relations were determined for both twitches and tetani by altering muscle length. Tx muscles showed an elevated stress-independent or activation heat (intercept of the heat-stress relation), a depressed stress-dependent heat (slope of the heat-stress relation), and greatly enhanced peak twitch and tetanic (Smax) stresses. When normalized for Smax, the maximal rates of tetanic stress development and heat production were depressed in the Tx group. In the T3 group, only the normalized maximal rate of tetanic stress development was significantly increased. The lack of significant effects on other mechanical and energetic parameters probably reflects an under-dosing of animals in this tri-iodothyronine-treated group, an interpretation supported by the modest change in isomyosin distribution resulting from the treatment regimen used. Separate isomyosin analyses of papillary muscles and their associated ventricles yielded excellent correlation demonstrating the suitability of papillary muscles as a model of ventricular wall tissue. By experimentally manipulating the thyroid state, the distribution of the three ventricular isomyosins were correspondingly altered with a shift toward a greater and lesser proportion of high activity myosin ATPase in the hyperthyroid and hypothyroid groups respectively. The average proportions of the myosin heavy chain associated with high actin-activated myosin ATPase were 86, 74 and 6% for groups T3, C and Tx respectively. The measured changes in papillary muscle energetics correlate well with these thyroid-induced changes in isomyosin distribution and can be explained in terms of altered crossbridge dynamics.

Analysis of Variance↗
PubMed1981

Isomyosins in human type 1 and type 2 skeletal muscle fibres.

Human myosin from different skeletal muscles was analysed in a non-denaturing gel system, and the isoenzyme composition correlated with the histochemical composition of the muscle. Two components (SM1 and SM2) were associated with type 1 (slow-twitch) fibres, and three (FM1, FM2 and FM3) with type 2 (fast-twitch) fibres. Light-chain analysis was performed in sodium dodecyl sulphate/polyacrylamide gels. There are three light chains (LCs1a, LCS1b and LCs2) in type 1 fibres, and three (LCf1, LCf2 and LCf3) in type 2 fibres. LCf1 and LCs1b co-migrate in sodium dodecyl sulphate gels. The ratio of LCf3/LCf2 is correlated with the distribution of the individual fast isoenzymes. These results explain apparent discrepancies in the literature concerning the light-chain distribution of human myosin.

Electrophoresis↗
PubMed1981

Contractile properties and ultrastructure of extensor digitorum longus and soleus muscles in spinal cord transected rats.

The spinal cord of rats 25 days of age was transected at the thoracic level, and the contractile properties as well as the ultrastructure of their extensor digitorum longus (EDL) and soleus muscles was examined. In the normally slow-twitch soleus muscle, the operation produces a marked reduction of contraction time as well as the appearance of other contractile characteristics of a fast-twitch muscle, namely, post-tetanic potentiation and cooling potentiation of the isometric twitch. This operation has little effect on the fast-twitch EDL. The ultrastructure of the EDL is similarly unaffected by the motor paralysis introduced by transection, but little change to the soleus structure was found, except for an increase in sarcoplasmic reticulum surface to fibre volume ratio. These results provide little evidence that muscle structure, especially the amount of sarcoplasmic reticulum, plays a major role in the determination of contractile speed, and confirms that structure may be regulated independently by the nerve.

Animals↗