Search PubMed⌕ Search

Biomedical subjects

D Pette

Publications and source records attributed to D Pette.

At least 127 records · Page 7Linked to original sources
PubMed1992

Effect of thyroid status on the expression of metabolic enzymes during chronic stimulation.

The effect of thyroid status on the expression of cytochrome c oxidase (CYTOX) and the activities of citrate synthase (CS) and phosphofructokinase (PFK) were examined in chronically stimulated (10 Hz; 35 days) and contralateral, nonstimulated rat tibialis anterior muscle of hypothyroid, hyperthyroid, and euthyroid animals. Stimulation increased CYTOX activity by 2.7-, 3.2-, and 4.9-fold in hyperthyroid, euthyroid, and hypothyroid animals, respectively, to similar absolute values. CS displayed similar increases. Stimulation reduced PFK activity in hypothyroid and euthyroid animals to 45% and 60% of control values. This effect was abolished with hyperthyroidism. Thus stimulation and thyroid hormone act antagonistically on PFK activity. Stimulation increased CYTOX subunit III (mitochondrially encoded) mRNA by 2.5- and 2.9-fold in hyperthyroid and euthyroid animals. Similar increases were observed in the nuclear-encoded mRNAs of CYTOX subunit VIc in euthyroid muscle. In hyperthyroid and euthyroid conditions, the mRNA changes paralleled the increases in enzyme activity. In hypothyroid muscle, the increase in mRNA was less for subunit VIc than III, suggesting that hypothyroidism upsets the coordinate expression of nuclear and mitochondrial genes. Further, the increases in CYTOX activity exceeded that of both subunit mRNAs in hypothyroid muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Altered gene expression in fast-twitch muscle induced by chronic low-frequency stimulation.

Increased neuromuscular activity via chronic low-frequency stimulation induces multiple fast-to-slow transitions in phenotypic properties that ultimately lead to fiber type conversions in the fast-twitch muscle of small mammals. Most of these alterations occur in an ordered sequence and result from the sequentially altered expression of myofibrillar and other protein isoforms. These changes relate to altered levels of specific mRNAs, followed by alterations in protein synthesis. As shown by the exchange of myosin heavy chain isoforms, protein degradation may be an additional control factor involved in the rearrangement of the myofibrillar apparatus. The degree of the various fast-to-slow transitions is species dependent and may be related to differences in thyroid hormone levels. It is suggested that the drastically and persistently depressed phosphorylation potential of the ATP system possibly serves to trigger the transformation process.

Animals↗
PubMed1992

Fast-to-slow transition in myosin heavy chain expression of rabbit muscle fibres induced by chronic low-frequency stimulation.

An in situ-hybridization assay using a digoxigenin-labeled cRNA probe specific for the slow myosin heavy chain (HCI) was established. Type I fibres of normal rabbit muscles were stained with this probe. The reaction product was confined to the perinuclear regions of the subsarcolemmal space and extended along the I-bands into the fibre core region. Myosin HCI mRNA was also detected in transforming fibres of low-frequency stimulated rabbit fast-twitch muscles. Its intracellular distribution resembled that of normal type I fibres, but higher amounts of the message were present in fibres undergoing a fast-to-slow transition. The number of HCI mRNA-positive fibres in stimulated muscles increased in a time-dependent manner and correlated with the amount of myosin HCI protein in these muscles. These findings support the notion that enhanced transcription of the slow myosin HC gene leads to an increased translation of HCI mRNA during the stimulation-induced fibre transformation. Finally, the progressive increase in fibres expressing myosin HCI mRNA indicates that the fast-to-slow fibre conversion occurs in a sequential manner. The pre-existing type IIA fibres appear to transform first, whereas fibre types IIB and IID have to first reach the IIA state. Adult muscle fibers represent versatile entities and may be transformed in response to altered functional demands. Although the majority of normal muscle fibers express only a single myosin HC isoform (for review see Pette and Staron, 1990), the coexistence of two or more myosin HC isoforms has been shown in transforming adult muscle fibers (Staron, Gohlsch, Pette, 1987; Termin, Staron, Pette, 1989).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Separation of active and inactive (nonphosphorylating) Ca(2+)-ATPase in sarcoplasmic reticulum subfractions from low-frequency-stimulated rabbit muscle.

Chronic low-frequency stimulation elicits in rabbit fast-twitch muscle a partial inactivation of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase and Ca(2+)-uptake activities. Inactive Ca(2+)-ATPase was enriched in a light microsomal fraction by sucrose density gradient centrifugation after calcium oxalate loading in the presence of ATP. This fraction showed a reduced specific activity and phosphoprotein formation of the Ca(2+)-transport ATPase. These results suggest that the inactivation of the Ca(2+)-ATPase as induced by increased contractile activity, is confined to a specific SR vesicle population.

Animals↗
PubMed1991

Altered glucose 1,6-bisphosphate and fructose 2,6-biphosphate levels in low-frequency stimulated rabbit fast-twitch muscle.

Glucose 1,6-bisphosphate (Glc-1,6-P2) and fructose 2,6-bisphosphate (Fru-2,6-P2) concentrations display pronounced increases in rabbit fast-twitch muscle during chronic low-frequency stimulation. These increases are first seen after stimulation periods exceeding 3 h and reach maxima after 12-24 h of stimulation (approximately 3-fold for Glc-1,6-P2 and 5-fold for Fru-2,6-P2). Both metabolites regress to normal values after stimulation periods longer than 4 days. The fact that their increases coincide with the replenishment of glycogen after its initial depletion, could point to a role of Glc-1,6-P2 and Fru-2,6-P2 in glycogen metabolism.

Animals↗
PubMed1991

Myosin heavy-chain-based isomyosins in developing, adult fast-twitch and slow-twitch muscles.

A modified method of electrophoresis under nondenaturing conditions made it possible to separate rat muscle extracts of defined myosin heavy chain (HC) and light chain (LC) composition into subsets of developmental, fast and slow myosin heavy-chain-based isomyosins. The fastest migrating isomyosins were the neonatal isomyosins (nM1, nM2, nM3), followed by the slightly slower migrating embryonic isomyosins (eM1, eM2, eM3, eM4). Of the nine adult fast isomyosins, the HCIIb-based isomyosins (FM1b, FM2b, FM3b) were the fastest migrating. These were followed by the HCIId-based isomyosins (FM1d, FM2d, FM3d). The HCIIa-based isomyosins (FM1a, FM2a, FM3a) were the slowest. Our results suggest that FM3a is identical with the so-called intermediate isomyosin (IM) described in the literature. The slow myosin heavy-chain-based isomyosins (SM1, SM2, SM3) migrated far behind the fast isomyosins. Whereas the gross electrophoretic mobilities of each of these isomyosin triplets is determined by the specific heavy chain complement, the different mobilities of the bands within each triplet result from different alkali light chain combinations. Thus, the fastest triplet bands of the neonatal (nM1) and adult fast isomyosins (FM1b, FM1d, FM1a) represent the LC3f homodimers, the slowest (nM3, FM3b, FM3d, FM3a) the LC1f homodimers, and the intermediate bands (nM2, FM2b, FM2d, FM2a) the LC1f/LC3f heterodimers. Different proportions of the adult fast isomyosin triplet bands indicate that the affinity for LC3f decreases in the order HCIIb, HCIId, HCIIa. The three slow isomyosins represent LC1sa (SM1) and LC1sb (SM3) homodimers and a LC1sa/LC1sb heterodimer (SM2). Circumstantial evidence suggests an inverse order in rabbit muscle where SM1 and SM3 most likely represent LC1sb and LC1sa homodimers, respectively.

Animals↗
PubMed1991

Fiber type-specific distribution of parvalbumin in rabbit skeletal muscle. A quantitative microbiochemical and immunohistochemical study.

A highly sensitive sandwich ELISA for parvalbumin (PA), based on a fluorometric detection system, was developed. This assay detected PA concentrations as low as 20 pg/ml (2 pg per assay) and was used for measuring PA contents in fragments of single muscle fibers isolated from freeze-dried 100-150 microns thick cross sections. The fibers were typed according to their histochemically assessed mATPase in parallel cross sections. Type I fibers from rabbit tibialis anterior (TA) and vastus lateralis (VL) muscles contained extremely low PA concentrations (2-5 micrograms/g w.wt.). Type IIA fibers displayed slightly higher values with mean values of 17 and 29 micrograms/g w.wt. (range 5-65) in TA and VL, respectively. Much higher PA concentrations were found in type IIB fibers with wide ranges from 75-1150 micrograms/g w.wt. in TA and 440-1370 micrograms/g w.wt. in VL. Whereas the IIB fibers of the TA displayed a continuum, two subgroups were distinguishable according to their PA contents (means of 590 and 1230 micrograms/g w.wt.) in VL. Possibly, the population with the lower PA content which was histochemically defined as type IIB in the present study, corresponds to fiber type IID. The finding that PA is predominantly present in type IIB fibers was also confirmed by the parallel decay of PA and type IIB fibers during chronic low-frequency stimulation. The use of freeze substitution, or alternatively, of freeze-drying, made it possible to demonstrate PA immunohistochemically without artifacts and to evaluate the staining intensity by microphotometry.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Enzyme activities of fatty acid oxidation and the respiratory chain in chronically stimulated fast-twitch muscle of the rabbit.

Fast-twitch tibialis anterior muscle of the rabbit was subjected to chronic low-frequency (10 Hz, 10 h/day) stimulation for different time periods up to 28 days. Total cellular activities of carnitine:palmitoyl-CoA transferase, crotonase, 3-hydroxyacyl-CoA dehydrogenase, 3-keto-acyl-CoA thiolase, citrate synthase, NADH:cytochrome c oxidoreductase, succinate: cytochrome c oxidoreductase, and cytochrome c oxidase were measured in contralateral and stimulated muscles at various times. With the exception of crotonase, which increased only 1.6-fold after 28 days of stimulation, the other enzymes increased in parallel displaying 3-fold elevated absolute activities. These results, by supporting and extending our previous findings, indicate that the expression of the enzymes of the main metabolic systems of aerobic substrate oxidation, i.e. the citric acid cycle, the fatty acid oxidation and the respiratory chain, is regulated in a coordinate manner.

Animals↗
PubMed1990

Electrophoretic separation by an improved method of fast myosin HCIIb-, HCIId-, and HCIIa-based isomyosins with specific alkali light chain combinations.

An improved method of electrophoresis under nondenaturing conditions separated three electrophoretically distinct isomyosin triplets when applied to rat fast-twitch muscles displaying a predominance of one of the fast myosin heavy chain isoforms HCIIb, HCIId or HCIIa. The three isomyosin triplets, named FM1b-FM3b, FM1d-FM3d, FM1a-FM3a, corresponded to the three possible alkali light chain (LC) combinations (LC1f homodimer, LC1f/LC3f heterodimer, and LC3f homodimer) with each fast HC isoform. Different proportions of these various isomyosins suggested specific affinities of light chains LC1f and LC3f for the fast heavy chain isoforms.

Animals↗
PubMed1990

Chronic low-frequency stimulation of rabbit fast-twitch muscle induces partial inactivation of the sarcoplasmic reticulum Ca2(+)-ATPase and changes in its tryptic cleavage.

Persistently increased contractile activity as induced by low-frequency stimulation in fast-twitch rabbit muscle elicits a partial inactivation of the sarcoplasmic reticulum Ca2(+)-ATPase function with regard to Ca2+ transport and ATP hydrolysis. Electron microscopy showed no differences in the frequency and structure of the two-dimensional Ca2(+)-ATPase crystals between microsomal fractions from normal and stimulated muscles. However, differences existed between the tryptic digestion of the Ca2(+)-ATPase in both the membrane-bound and solubilized enzyme at the first tryptic cleavage site, named T1 (Arg505). This followed from a delayed appearance of the A and B fragments of the Ca2(+)-ATPase in the electrostimulated muscle. No differences existed with regard to the second tryptic cleavage site, named T2 (Arg198). Confirming previous results, fluorescein isothiocyanate (FITC) binding to the enzyme of the chronically stimulated muscle was markedly reduced. The FITC-labeled fraction of the enzyme from both the normal and the stimulated muscle followed similar time courses of tryptic cleavage. The fraction of Ca2(+)-ATPase that did not bind TITC was identified by immunoblot analysis as the trypsin-resistant form. In view of the vicinity of T1, the FITC- and the ATP-binding sties, these results point to a modification of the enzyme in that region leading to an inactivation of about 50% of the sarcoplasmic reticulum Ca2(+)-ATPase molecules.

Animals↗
PubMed1990

Antagonistic effects of chronic low frequency stimulation and thyroid hormone on myosin expression in rat fast-twitch muscle.

This study investigates effects of chronic low frequency stimulation (CLFS) on myosin heavy (MHC) and light chain (MLC) expression in fast-twitch muscles in hypothyroid, euthyroid, and hyperthyroid rats. The changes at both the mRNA and protein level indicated antagonistic effects of thyroid hormone and CLFS: under euthyroid conditions, CLFS mainly elicited a MHCIIb----MCHIId----MHCIIa transition. Whereas CLFS did not induce the slow MHCI in the euthyroid state, this isoform was present in the hypothyroid state and was further enhanced with CLFS indicating the suppressive effect of thyroid hormone to be stronger than the inductive influence of CLFS. Hyperthyroidism alone suppressed the expression MHCIIa and enhanced a MHCIId to MHCIIb transition. This shift to the faster MHC isoforms was only partially counteracted by CLFS. Thus, it appeared that thyroid hormone had a graded suppressive effect on the expression of MHC isoforms in the order MHCIId less than MHCIIa less than MHCI. Elevated neuromuscular activity partially counteracted these hormone effects. Changes in MLC mRNAs were consistent with those in the MHC pattern, i.e. increases or decreases in MHCIIb led to corresponding changes in the expression of MLC3f. A similar relationship existed for the slow MHCI and the slow MLC isoforms.

Animals↗
PubMed1990

Rapid and reversible changes in myosin heavy chain expression in response to increased neuromuscular activity of rat fast-twitch muscle.

Chronic 10 Hz stimulation of rat fast-twitch muscle induced rapid and reversible changes in the tissue levels of fast myosin heavy chain (HC) mRNA isoforms. These changes consisted of a rapid decrease in HCIIb mRNA and a progressive increase in HCIIa mRNA. After 15 days, the HCIIb mRNA normally amounting to approximately 80%, had decreased to less than 5% of the sum of the two HC mRNA isoforms. HCIIb mRNA was again detectable one day after cessation of stimulation and progressively increased at the expense of HCIIa mRNA with ongoing recovery. These results point to a down-regulation of the HCIIb gene by the applied stimulus pattern which, conversely, enhances the expression of the HCIIa gene.

Animals↗
PubMed1990

Changes in free and bound forms and total amount of hexokinase isozyme II of rat muscle in response to contractile activity.

Increased contractile activity as induced by chronic low-frequency stimulation evoked in rat fast-twitch muscle an almost immediate increase in the ratio between structure-bound and free hexokinase. In addition, an up to 14-fold rise in total hexokinase activity occurred after two weeks of stimulation indicating that glucose phosphorylation became a limiting step of glucose utilization under these conditions. The increase in hexokinase activity was transitory as prolonged stimulation led to a leveling off and steep decline with an apparent half-life of 2.5 days after three weeks of stimulation. The transient increase in glucose phosphorylating capacity can be explained by previous observations indicating that prolonged stimulation leads to a shift from a carbohydrate-based to a fatty-acid-based energy metabolism. Using an isozyme-specific sandwich ELISA, it was shown that both increases and decreases in total hexokinase activity were matched by corresponding changes in the amount of hexokinase isozyme II protein. Increases in both total hexokinase activity (3-4-fold) and hexokinase II protein content were also observed after denervation in rat fast-twitch muscle. In view of reports in the literature, it is suggested that the elevations in hexokinase II observed with increased contractile activity and denervation relate to enhanced glucose uptake and utilization.

Animals↗
PubMed1990

Chronic stimulation-induced effects point to a coordinated expression of carbonic anhydrase III and slow myosin heavy chain in skeletal muscle.

Chronic low-frequency stimulation of rat fast-twitch muscle induces 3.7-fold elevations in cytochrome c oxidase activity, but remains without effect on carbonic anhydrase III (CAIII) mRNA and protein. This is in contrast with the situation in the rabbit where chronic stimulation elicits more than 10-fold elevations in CAIII activity and mRNA content which coincide with an enhanced expression of the slow myosin heavy chain (HCI). Since chronic stimulation of rat muscle does not enhance the expression of HCI, we conclude that CAIII is expressed in parallel with HCI and, therefore, is present only in type I and C fibers.

Animals↗
PubMed1990

Fast and slow isoforms of troponin I and troponin C. Distribution in normal rabbit muscles and effects of chronic stimulation.

Polyclonal antibodies were raised against troponin I (TnI) and troponin C (TnC) purified from fast-twitch and slow-twitch rabbit muscles. These antibodies were used to elucidate the distribution of fast and slow isoforms of TnI and TnC in normal and chronically stimulated rabbit hind limb muscles by immunoblots of one-dimensional and two-dimensional electrophoreses. In contrast to the multiplicity of fast and slow troponin T (TnT) isoforms, TnI and TnC were present as unique fast and slow isoforms. Whereas no charge variants were detected for slow TnI, fast TnI was present in at least three charge variants. As judged from the results of alkaline phosphatase digestion, these charge variants represent differently phosphorylated forms. Fast and slow TnC both exist as two charge variants which, however, were unaffected by alkaline phosphatase treatment. Chronic low-frequency stimulation of fast-twitch muscles induced progressive increases in the slow isoforms of TnC and TnI at the expense of their fast isoforms. The extent of the fast-to-slow transition was more pronounced in the case of TnC than in that of TnI. Long-term stimulated muscles with a complete fast-to-slow transition, at the level of the TnT isoforms, still contained fast and slow isoforms of both TnI and TnC. The coexistence of fast and slow isoforms of the three troponin subunits in the transforming muscle was interpreted as indicating the presence of hybrid troponin molecules composed of fast and slow isoforms. Studies at the mRNA level showed changes similar to those at the protein level. However, in long-term stimulated muscles, the fast-to-slow transition of TnI was more pronounced at the mRNA level than at the protein level.

Animals↗
PubMed1990

Rapid up- and down-regulation of hexokinase II in rat skeletal muscle in response to altered contractile activity.

An up to 14-fold increase in total hexokinase activity induced by low-frequency stimulation in rat fast-twitch muscle was followed by a rapid decay in enzyme activity after cessation of stimulation. In vivo labeling revealed that these alterations were related to rapid changes in [35S]methionine incorporation into hexokinase II. A recovery period of 15 h after cessation of stimulation was sufficient to normalize the approximately 30-fold elevated [35S]methionine incorporation.

Animals↗