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Biomedical subjects

D Pette

Publications and source records attributed to D Pette.

At least 217 records · Page 12Linked to original sources
PubMed1983

Changes in transcriptional activity of chronically stimulated fast twitch muscle.

mRNAs extracted from rabbit soleus, normal and 28-day, indirectly stimulated tibialis anterior muscles were translated in an in vitro system. Analysis for translation products by 2-dimensional electrophoresis showed fast myosin light chains in tibialis anterior, and slow myosin light chains in soleus muscle. The stoichiometry of the in vitro translated light chains varies from that seen in normal fast and slow twitch muscles. The stimulated muscle contained mRNA coding, both for fast and slow myosin light chains, although the pattern of slow myosin light chains appears not to be complete at this point of time of the transformation process.

Animals↗
PubMed1983

Two telestimulation systems for chronic indirect muscle stimulation in caged rabbits and mice.

Telestimulation systems are described for chronic indirect muscle stimulation in caged rabbits and mice. Both systems use a 5 MHz carrier frequency transmission and consist of a transmitter and a receiver. The latter is fixed to the back of the animal. The system for rabbits uses pulse width modulation for transmitting stimulation frequency and amplitude. Duration of the stimulation impulse is generated in the receiver. Clock batteries in the receiver generate impulse energy. The impulse amplitude varies by only 1%. In the system used for mice, impulse energy is transmitted together with the stimulation frequency. This is achieved by a receiver containing two separate coils which are opposed to each other in an angle of 80 degrees C. In contrast to the rabbit system, the duration of the stimulation impulse is generated by the impulse width of the 5 MHz carrier. The amplitude of the stimulation impulse depends on the amplitude of the carrier. Due to the geometry of induction coil and receiver, impulse intensity varies at maximum by only 10%.

Animals↗
PubMed1983

Ipsi- and contralateral fibre transformations by cross-reinnervation. A principle of symmetry.

Cross-reinnervation of rabbit soleus muscle by the peroneal nerve induces a 90% transformation of slow into fast fibres. These changes are reflected in corresponding transformations of the enzyme activity pattern of energy metabolism, the isozyme pattern of lactate dehydrogenase and, in confirmation of previous results (Srihari et al. 1981), transitions from a slow to a fast type myosin light chain pattern. The transformation process appears to be complete after 6 months. Similar changes, although less extensive are also found in the soleus muscle of the contralateral leg. Fibre type transitions in the contralateral muscle are not accompanied by fibre type grouping, as seen in the cross-reinnervated muscle and therefore these changes appear to result from a transformation of the motor units themselves. This phenomenon is interpreted as a compensatory process in maintaining symmetry within the neuromotor system.

Animals↗
PubMed1983

Relationships between early alterations in parvalbumins, sarcoplasmic reticulum and metabolic enzymes in chronically stimulated fast twitch muscle.

The present study compares the time courses of the early changes in parvalbumin content, in the properties of the sarcoplasmic reticulum (SR) and in activity and isozyme patterns of metabolic enzymes in chronically (12 h/day) stimulated fast twitch tibialis anterior (TA) muscle of the rabbit. Under the chosen conditions of stimulation, the first significant changes appeared after 6 days. Except for the delayed reduction in pyruvate kinase, the time course of the changes were the same. After 14 days of stimulation, parvalbumin decreased to 37% and Ca2+-ATPase activity of the SR to 29% of normal values. The transformation of the SR was also reflected by a 64% decrease of the 115000-Mr Ca2+-pumping peptide and a 5-fold increase in a 30000-Mr peptide. Following an identical time course, the mitochondrial activities of citrate synthase, 3-hydroxyacyl-CoA dehydrogenase and ketoacid-CoA transferase increased 2.9, 3.0 and 3.7-fold respectively. A similar time course was observed in the M to H-type transition of the lactate dehydrogenase isozymes. The cause of these changes is discussed as it relates to altered transcriptional and/or translational activities. It is suggested that an increase in free intracellular Ca2+ caused by increased contractile activity, which is then perpetuated by the decrease in Ca2+-binding and sequestering capacities, might be the signal for such altered synthetic activities.

Animals↗
PubMed1983

Fibre type specific transformations in the enzyme activity pattern of rat vastus lateralis muscle by prolonged endurance training.

The alterations in activity patterns of representative enzymes in energy metabolism were investigated in the superficial (white) and deep (red) portions of the fast vastus lateralis muscle of the adult rat in response to prolonged endurance training. It was found that following 15 weeks of extreme training (final running duration: 210 min per day, 27 m/min at 15 degree grade), increases in the activities of marker enzymes of the citric acid cycle (citrate synthase), beta-oxidation (3-hydroxyacyl CoA dehydrogenase), and ketone body utilization (3-ketoacid CoA transferase) as well as of glutamate pyruvate transaminase occurred in both regions of the muscle, with the greatest increase being observed in the superficial portion (2.6-4.2-fold). Pronounced increases were also seen for hexokinase which showed highest activities after 7 weeks of training. Conversely, decreases were noted for various glycogenolytic, glycolytic and gluconeogenic enzymes (phosphorylase, glyceraldehydephosphate dehydrogenase, pyruvate kinase, lactate dehydrogenase and fructose-1,6-diphosphatase). Reduction in the activities of these enzymes was most pronounced in the deep portion of the muscle. These results demonstrate a fundamental rearrangement of the energy metabolism of the muscle in response to prolonged, high intensity training. In the case of the deep portion of the vastus lateralis muscle, which has been shown to be composed of a large percentage of fast oxidative-glycolytic fibres (FOG), the enzyme profile becomes similar to the slow oxidative (SO) fibre. In the superficial portion which contains predominantly fast glycolytic fibres (FG), the enzyme profile becomes similar to FOG fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

An automated micropipet especially designed for use with the oil-well technique.

A high-precision microprocessor-controlled micropipetting unit which is applicable for serial enzyme or substrate microdeterminations with the oil-well technique is described. Positioning of the reaction wells, pipetting of microliter and submicroliter volumes, as well as measurements of incubation times are performed automatically following an adjustable present program.

Autoanalysis↗
PubMed1983

Response of succinate dehydrogenase activity in fibres of rabbit tibialis anterior muscle to chronic nerve stimulation.

Succinate dehydrogenase activity (SDH) was estimated kinetically in individual muscle fibres from the rabbit tibialis anterior, in cryostat sections using computer-linked microphotometry to record initial reaction velocities. These were correlated with fibre type based on myofibrillar actomyosin ATPase staining. Analysis of type IIA and IIB fibre populations in control muscles demonstrated wide variations in SDH activity between fibres of identical myosin ATPase type, with a considerable overlap in oxidative activities of the IIA and IIB populations. Muscles chronically stimulated via the peroneal nerve, using two different frequency patterns, showed increases in SDH activity which were primarily located in the type IIB fibres. This increase was observed both in muscles stimulated continuously at 10 Hz, and when similar numbers of stimuli were applied in brief trains at higher frequency. An earlier onset and more rapid rate of increase of SDH activity was seen with 10 Hz stimulation than with higher frequency, though the levels after 14 days of either pattern of stimulation were not significantly different.

Adenosine Triphosphatases↗
PubMed1982

The control of glucose 1,6-bisphosphatase by Ca2+ and calmodulin.

1. The control of glucose 1,6-bisphosphatase activity, the enzyme that degrades glucose 1,6-bisphosphate, a metabolite that regulates hexose phosphate metabolism, has been examined in a rat muscle extract. 2. The enzyme has been found to be activated by physiological Ca2+ concentrations. Ca2+ can be replaced by Sr2+ and Mn2+, but the effects are not so pronounced. 3. The Ca2+ effect is inhibited by EGTA. Trifluoperazine also inhibits enzyme activity. This effect can be reversed by adding exogenous calmodulin.

Animals↗
PubMed1982

The control of glucose 1,6-bisphosphate by developmental state and hormonal stimulation in cultured muscle tissue.

1. The concentration of glucose 1,6-bisphosphate, a potent regulator of muscle glucose metabolism, was examined in embryonic muscle cells in culture. 2. The concentration in fused myotubes was twice that in unfused myoblasts. 3. The effect of various hormones and agonists on the glucose 1,6-bisphosphate concentration in both pre- and post-fusion muscle cells was examined. In pre-fusion cells no effect of adrenaline or cyclic AMP was observed, but stimulation by vasopressin, adrenaline + propranolol, ionophore A23187 and dibutyryl cyclic GMP significantly decreased glucose 1,6-bisphosphate. In post-fusion cells similar effects were observed, except that stimulation by adrenaline and by dibutyryl cyclic AMP significantly increased metabolite concentration. 4. All effects increased with time (over a 1 h period), except for that of vasopressin, which was transient. 5. The changes in glucose 1,6-bisphosphate concentration were accompanied by changes in the fructose 1,6-bisphosphate/fructose 6-phosphate ratio, implying an effect on phosphofructokinase activity.

Animals↗
PubMed1982

The breakdown of phosphatidylinositol in myoblasts stimulated to fuse by the addition of Ca2+.

1. The fusion of chick-embryo myoblasts to produce myotubes was studied. The myoblasts were grown for 50 h in medium containing 10--20 microM-Ca2+; during this period they achieve fusion competence. 2. A rapid breakdown of phosphatidylinositol is also observed on addition of 1.4 mM-Ca2+ to these cells. This Ca2+ concentration also stimulates rapid myoblast fusion. 3. The breakdown is complete within 15 min and shows the same dependence on Ca2+ concentration as the fusion process. 4. Fusion-incompetence myoblasts and cells where fusion is inhibited by sodium butyrate exhibit no phosphatidylinositol breakdown on Ca2+ addition. 5. The Ca2+ ionophore A23187 inhibits the Ca2+-stimulated breakdown by about 50%, but has no effect on fusion. 6. A concomitant increase in 1,2-diacylglycerol labelled and fall in phosphatidylinositol labelling was observed when the lipids were labelling with [14C]glycerol on increasing the Ca2+ concentration in the medium to 1.4 mM. 7. We propose that the breakdown of phosphatidylinositol with a resultant increase in 1,2-diacylglycerol content of the cell membrane promotes myoblast fusion.

Animals↗
PubMed1982

A comparison of two ATPase based schemes for histochemical muscle fibre typing in various mammals.

A comparative study was performed on the fibre populations in tibialis anterior muscles of mouse, rat, guinea pig, rabbit, cat and dog using the two different methods of histochemical staining for myofibrillar ATPase after acid (Brooke and Kaiser 1970) or alkaline preincubations (Guth and Samaha 1970). For all species a complete correspondence existed between type I (Brooke and Kaiser 1970) and beta fibres (Samaha et al. 1970). Gross correspondence (greater than 85%) existed between IIA and IIB (Brooke and Kaiser 1970) and alpha beta and alpha fibres (Samaha et al. 1970) respectively in mouse, guinea pig, rabbit, cat and dog. In the case of mouse and dog, this high degree of correspondence was based on the assumption that mouse tibialis anterior contains no type I and the dog no type IIB fibres. For the rat, a pronounced overlap existed between IIA fibres on the one hand and alpha beta and alpha fibres on the other hand as well as between IIB fibres and alpha beta and alpha fibres. These observations lead to the conclusion that the two classification schemes are not interchangeable for all species and that the two terminologies should be used only in relation with the methods from which they were derived.

Adenosine Triphosphatases↗
PubMed1982

A comparative microphotometric study of succinate dehydrogenase activity levels in type I, IIA and IIB fibres of mammalian and human muscles.

Activity levels of succinate dehydrogenase (SDH) were determined kinetically by means of comparative microphotometric measurements in situ. Activities were correlated with fibre types classified histochemically according to Brooke and Kaiser (1970). Analyses of tibialis anterior muscles in the mouse, rat, guinea pig, rabbit, cat and the human showed pronounced variations in the activity profiles of type I, type IIA and IIB fibres of these muscles. Large scattering of enzyme activity existed in three fibre populations. Overlaps of varying extent were found for the SDH profiles between the different muscles. Type I fibres reveal species differences in aerobic oxidative capacity. Whereas the majority of the IIB fibres in rabbit muscle tended to be low in SDH activity, the main fraction of this fibre population was characterized by high activities in mouse muscle. Similarly, the IIA fibre populations revealed opposite properties in mouse and rabbit muscles. These extremes as well as intermediate activity patterns indicate that no general scheme exists according to which the histochemically assessable myosin ATPase is correlated with the aerobic oxidative capacity of muscle fibres in various mammalian muscles.

Adolescent↗
PubMed1982

The effect of different patterns of long-term stimulation on contractile properties and myosin light chains in rabbit fast muscles.

Fast rabbit skeletal muscles (tibialis anterior and extensor digitorum longus) were stimulated for 2-28 days by electrodes implanted in the vicinity of the peroneal nerve to produce maximal contractions at two different frequency patterns: that occurring naturally in nerves to slow muscles (10 Hz continuously) or three bursts of tetani (40 Hz) per minute, each 5s in duration. Both types of frequency produced muscles more resistant to fatigue during isometric twitch contractions, and led to a prolongation of contraction time greater and more consistent with 10 Hz than with 40 Hz. The twitch/tetanus ration was significantly higher in muscles stimulated at 10 Hz for 3-4 weeks but was not different from controls in muscles stimulated at 40 Hz. Both types of stimulation led to the appearance of myosin light chains characteristic of slow muscles. Muscles stimulated for 4 weeks at 40 Hz developed greater twitch tension per gram, and had significantly smaller cross-sectional area of myofibrils than control muscles. It is concluded that long-term electrical stimulation of fast muscles can affect some muscle contractile properties to resemble those of slow muscles irrespective of frequency of stimulation, provided the total number of stimuli is comparable, the duration of stimulation is long enough (minimum 2 weeks) and all motor units are activated.

Animals↗