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D Pette

Publications and source records attributed to D Pette.

At least 19 recordsLinked to original sources
PubMed1992

Time-dependent increases in Na+,K(+)-ATPase content of low-frequency-stimulated rabbit muscle.

Chronic low-frequency stimulation of rabbit fast-twitch muscle induced time-dependent increases in the concentration of the sarcolemmal Na+,K(+)-ATPase and in mitochondrial citrate synthase activity. The almost twofold increase in Na+,K(+)-ATPase preceded the rise in citrate synthase and was complete after 10 days of stimulation. We suggest that the increase in Na+,K(+)-ATPase enhances resistance to fatigue of low-frequency-stimulated muscle prior to elevations in aerobic-oxidative capacity.

Animals↗
PubMed1992

Inactivation of sarcoplasmic-reticulum Ca(2+)-ATPase in low-frequency-stimulated muscle results from a modification of the active site.

Molecular changes underlying the partial inactivation of the sarcoplasmic-reticulum (SR) Ca(2+-) ATPase in low-frequency-stimulated fast-twitch muscle were investigated in the present study. The specific Ca(2+)-ATPase activity, as well as the ATP- and acetyl phosphate-driven Ca2+ uptakes by the SR, were reduced by approx. 30% in 4-day-stimulated muscle. Phosphoprotein formation of the enzyme in the presence of ATP or Pi was also decreased to the same extent. Measurements of ATP binding revealed a 30% decrease in binding to the enzyme. These changes were accompanied by similar decreases in the ligand-induced (ATP, ADP, Pi) intrinsic tryptophan fluorescence. A decreased binding of fluorescein isothiocyanate (FITC) corresponded to the lower ATP binding and phosphorylation of the enzyme. Moreover, Pi-induced changes in fluorescence of the FITC-labelled enzyme did not differ between SR from stimulated and contralateral muscles, indicating that Ca(2+)- ATPase molecules which did not bind FITC were responsible for the decreased Pi-dependent phosphorylation, and therefore represented the inactive form of the enzyme. No differences existed between the Ca(2+)-induced changes in the intrinsic fluorescence of SR from stimulated and contralateral muscles which fit their similar Ca(2+)-binding characteristics. Taking the proposed architecture of the Ca2(+)-ATPase into consideration, our results suggest that the inactivation relates to a circumscribed structural alteration of the enzyme in sections of the active site consisting of the nucleotide-binding and phosphorylation domains.

Adenosine Triphosphate↗
PubMed1992

Changes in myosin heavy-chain isoform synthesis of chronically stimulated rat fast-twitch muscle.

Chronic low-frequency stimulation was used for studying the adaptive potential of rat fast-twitch muscle to increased neuromuscular activity. The sequential exchange of myosin heavy chain isoforms HCIIb with HCIId and HCIIa was studied at the translational level using an in-vivo-labeling technique with [35S]methionine. Alterations in heavy chain isoform synthesis, i.e. a decrease in the labeling of HCIIb concomitant with an enhanced labeling of HCIId/IIa, were detectable already two days after the onset of stimulation. This time course corresponds to the previously observed alterations in the amounts of HCIIb and HCIIa mRNAs. However, significant changes in the relative protein amounts of HCIIb and HCIId/IIa were recorded only after an 8-day stimulation period. This delay at the protein level was interpreted to relate to the slow turnover of HCIIb which was estimated from its decay in long-term stimulated muscles with an approximate value of 14.7 days. Therefore, protein degradation seems to be an important post-translational regulatory step in the remodeling process of the thick filament.

Animals↗
PubMed1992

Metabolite patterns related to exhaustion, recovery and transformation of chronically stimulated rabbit fast-twitch muscle.

Rabbit fast-twitch tibialis anterior muscle was subjected to chronic low-frequency stimulation (10 Hz, 24 h/day). Measurements of the time course of changes in the concentration of metabolites of energy metabolism were performed in order to test the hypothesis whether or not alterations in the metabolite profile might represent possible signals for triggering muscle fibre type transformation. Most of the investigated metabolites displayed triphasic changes in response to persistently increased contractile activity. During the first 15 min of stimulation, drastic reductions were observed for adenosine triphosphate (ATP, 56%), phosphocreatine (PCr, 60%) and glycogen (76%), as well as 3- to 4-fold and 10-fold increases for glucose and lactate, respectively. This early metabolic perturbance coincided with a rapid reduction of isometric force. The next phase, extending to 4 days of stimulation, was characterized by a nearly complete recovery of ATP and PCr, and an overshoot in glycogen. The first signs of metabolic recovery were already detectable in 60-min-stimulated muscle when isometric force was still markedly depressed. These results demonstrated an impressive capability of the muscle to recover with ongoing stimulation from an initial, dramatic disturbance in energy metabolism. During the final phase, extending to 50 days, the metabolite profile approached that of a slow-twitch muscle with moderate reductions in total adenine nucleotides, ATP, total creatine, PCr and glycogen. A conspicuous result was the finding that, contrary to the recovery of most metabolites, the ratio of ATP to the product of free adenosine diphosphate and resting free inorganic phosphate was persistently depressed with ongoing stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
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↗