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Biomedical subjects

D Pette

Publications and source records attributed to D Pette.

At least 235 records · Page 13Linked to original sources
PubMed1981

Correlation between ultrastructural and functional changes in sarcoplasmic reticulum during chronic stimulation of fast muscle.

Chronic indirect stimulation of fast twitch rabbit muscle (tibialis anterior and extensor digitorum longus) with a frequency of 10 Hz induced a progressive transformation of the sarcoplasmic reticulum (SR). Ultrastructural changes as studied by electron microscopy of freeze-fractured vesicles consisted in a decrease of intramembranous particles of the concave (A) face and an increase of particles in the convex (B) face. The asymmetry of the membrane proved to be lowered. Changes in the particle density of the A face were mainly confined to the 7-9 nm particles. Electrophoretic analyses revealed a decrease in the 115,000-Mr Ca2+ transport ATPase. The reduced density of the 7-9 nm particles correlated well with decreased activities in Ca2+-dependent ATPase as well as with decreases in initial and maximum Ca2+ uptake.

Animals↗
PubMed1981

Ipsi-and contralateral changes in rabbit soleus myosins by cross-reinnervation.

Cross reinnervation of soleus muscle in the adult rabbit induces changes in myosin light chain and isomyosin patterns. The transformation of the light chain pattern consists of a decrease in LC1's and LC2, and an induction of the three fast type myosin light chains. The transition in the isomyosin pattern consists of a decrease of the slow type isomyosin SM and an induction of fast type isomyosins FM1, FM2, and FM3 normally seen in fast-twitch rabbit muscle. An additional isomyosin of intermediate electrophoretic mobility, which resembles isomyosin 4 of rat muscle, is induced. These changes are not restricted to the cross-reinnervated soleus muscle but are also seen, although to a lesser extent, in the contralateral soleus muscle. It is suggested that the altered afferent activity brought about by cross-reinnervation, is neurally transmitted to the opposite side and leads to a change in efferent activity to the contralateral muscle.

Amino Acids↗
PubMed1981

Microphotometric measurement of initial maximum reaction rates in quantitative enzyme histochemistry in situ.

Final reaction product formation was recorded microphotometrically for succinate dehydrogenase in cross-sectioned muscle fibers at initial rate conditions and during prolonged incubations. Incubations with gel films and aqueous reaction medium both showed a decline of reaction rates. Maximum reaction rates could only be determined at initial rate conditions during the first minute of the incubation. Reaction rates recorded in different areas of the same tissue section were found to change with time to different degrees. From these results it was concluded that quantitative histochemical measurements of enzyme reactions in situ can only be valid if measured under initial maximum velocity conditions.

Animals↗
PubMed1981

Electrophoretic analyses of myofibrillar proteins from the body wall muscles of Ascaris suum.

A myofibrillar protein extract has been isolated from the muscle of Ascaris suum. Two-dimensional electrophoresis of this extract revealed that the myosin light chain 1 (ALC1) migrates as 3 components with approximate isoelectric points in the range of 5.3-5.6. The most acidic component of ALC1 appeared to be phosphorylated when the myofibrillar extract was incubated for 10 s with catalytic subunit of cAMP dependent protein kinase and [gamma-32P] ATP. The myosin light chain 2 (ALC2) migrated as a single component in isoelectric focusing with an approximate isoelectric point of 5.5 Actin was resolved into 2 components with identical molecular weight but isoelectric points differing by approximatley 0.2 pH units. A protein was tentatively identified in the myofibrillar extract as tropomyosin. It migrated as a single band with an approximate isoelectric point of 5.0 and a molecular weight of 39 000. None of the troponin components could be identified in the myofibrillar extract. It is postulated that muscle contraction in A. suum muscle could be controlled by phosphorylation of myosin.

Actins↗
PubMed1981

Comparison of enzyme activities among single muscle fibres within defined motor units.

1. Muscle fibres from single motor units of rat extensor digitorum longus were depleted of their glycogen by electrical stimulation and identified by the periodic acid-Schiff stain after treatment in a medium that selectively enhanced glycogen content in the non-depleted fibres. 2. Malate dehydrogenase (MDH) and fructose-1,6-diphosphatase (FDPase) activities were studied quantitatively in single dissected fibres of individual motor units and in fibres selected randomly from the same muscle. 3. In contrast to the large variability of MDH and FDPase in muscle fibres taken randomly, the muscle fibres from the same motor units had similar enzyme activities. 4. The resistance to fatigue of the motor units correlated well with the capacity of aerobic oxidative metabolism, as judged by the activity of MDH in the muscle fibres.

Animals↗
PubMed1981

Succinate dehydrogenase activity in fibres classified by myosin ATPase in three hind limb muscles of rat.

1. Succinate dehydrogenase (SDH) activity was assessed in situ in single fibres of cross-sectioned extensor hallucis longus, extensor digitorum longus, and soleus muscles of rat by means of microphotometric recordings of initial maximum reaction rates. 2. Each fibre assessed for SDH activity was subjectively classified into myosin subgroups by its histochemical reaction for myofibrillar actomyosin ATPase (myosin ATPase) following preincubation at pH 4.6 according to Brooke & Kaiser (1970). 3. The majority of fibres classified into myosin types I and IIa were highly reactive for SDH, such that those myosin groups could be interchangeable with the metabolic subgroups of Peter, Barnard, Edgerton, Gillespie & Stempel (1972); myosin I = slow-twitch oxidative, myosin IIa = fast-twitch oxidative glycolytic. 4. The myosin type IIb fibres, however, demonstrated marked variability in activity levels of SDH. Over 40% of those fibres had high SDH activity, and thus could not be equated with the metabolic subgroup fast-twitch glycolytic. 5. The histochemical reaction for myosin ATPase in muscle fibres therefore cannot be used as a reliable means to predict the fibres' metabolic characteristics.

Adenosine Triphosphatases↗
PubMed1980

Do enzyme activities vary along muscle fibres?

Distribution of succinate dehydrogenase activity along muscle fibres has been studied qualitatively by histochemistry on single micro-dissected rat muscle fibres and quantitatively by comparative kinetic microphotometry on longitudinal muscle sections. Qualitative staining reactions showed no appreciable variations in enzyme activity along the fibres regardless of fibre type. By quantitative assessment, minor variations were found along fibres but were within the range of the experimental error. These variations are of the same magnitude as those observed in enzyme activities of pieces of the same fibre by means of quantitative microchemical methods, performed in our laboratory (Spamer and Pette 1979; Nemeth et al. 1980a, b). Our results provide evidence that the enzyme levels are the same along the course of a muscle fibre.

Animals↗
PubMed1979

Activities of malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase and fructose-1,6-diphosphatase with regard to metabolic subpopulations of fast- and slow-twitch fibres in rabbit muscles.

Activities of malate dehydrogenase (MDH), 3-hydroxyacyl-CoA dehydrogenase (HAD) and fructose-1,6-diphosphatase (FDPase) were determined in single fibres dissected from freeze-dried rabbit psoas and soleus muscles. Slow-twitch fibres as determined by qualitative ATPase reaction represent a rather uniform population with regard to HAD and MDH activities. In these fibres the two enzymes are in constant proportions. FDPase is found at extremely low activities in slow-twitch fibres and because of its relatively high activity in fast-twitch fibres of soleus and psoas muscle it might be used as a marker enzyme. Fast-twitch fibres in psoas muscle represent a heterogeneous population with regard to activities of MDH as well as of HAD. The two enzyme activities are not proportional in fast-twitch psoas fibres. These findings suggest the existence of metabolic subpopulations of fast-twitch fibres having a wide range of aerobic oxidative capacities and having differences in their capacity to oxidizing fatty acids.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1979

Molecular transformations in sarcoplasmic reticulum of fast-twitch muscle by electro-stimulation.

Chronic electro-stimulation of fast-twitch rabbit muscle with the frequency pattern received by a slow-twitch muscle induces a progressive transformation of the sarcoplasmic reticulum. After 2 days stimulation activities of Ca2+-dependent ATPase and of Ca2+ transport begin to decrease, and are paralleled by a progressive decrease in Ca2+-dependent and Ca2+, Mg2+-dependent phosphoprotein formation, reduced rate of dephosphorylation and a rearrangement of the electrophoretic polypeptide and phosphoprotein patterns. These findings suggest a transformation of the sarcoplasmic reticulum to resemble that of a slow-twitch muscle. This transformation is paralleled by increase in time-to-peak of twitch contraction and half relaxation time and occurs before conversion of the myosin light chain pattern is observed. The parallel time course of changes in contractile properties of stimulated muscle and the molecular and functional properties of the sarcoplasmic reticulum emphasizes the definitive role of the latter in determining the twitch characteristics of fast and slow twitch muscles.

Adenosine Triphosphatases↗
PubMed1979

Independent development of contractile properties and myosin light chains in embryonic chick fast and slow muscle.

1. The contractile speeds and tetanus/twitch ratios of the slow anterior latissimus dorsi (ALD) and fast posterior latissimus dorsi (PLD) muscles were studied during embryonic development and correlated with the type of myosin light chains present in these muscles as studied by one and two dimensional polyacrylamide gel electrophoresis. 2. At a time when the contractions of PLD were slow, i.e. in 15 day old embryos, the myosin light chains in this muscle were of the fast type. The slow contraction of this muscle may be due to incomplete and slow activation of the contractile elements. The tetanus/twitch ratio of muscles from 15 day old embryos is low and increases sharply with age. This increase could be due to the maturation of the internal membrane system, and occurs at about the same time as the increase in the speed of contraction. 3. ALD muscles contract slowly during all stages of development, although their tetanus/twitch ratio also increases with age. At 13 days they contain a mixture of fast and slow type myosin light chains and with increasing age the proportion of the slow type myosin light chains increases at the expense of the fast type. The slow time course of contraction of ALD is consistent with the presence of slow type myosin light chains. 4. The possibility that the synthesis of the slow type myosin light chains in ALD is induced by early motor activity in chick embryos is discussed.

Age Factors↗
PubMed1979

The constant proportion enzyme group concept in the selection of reference enzymes in metabolism.

Comparative analyses of enzyme activity patterns reveal groups of enzymes with constant proportions and enzymes with variable proportions of their maximum activities. Constant proportion groups comprise enzymes of unbranched metabolic sequences or functionally related pathways. Ratios of constant proportion groups reflect metabolic correlations, which may be used as discriminative magnitudes of metabolic specialization. Comparison of closely related muscles reveals that differences in the absolute levels of the constant proportion group enzymes of glycolysis parallel differences in maximum glycolytic flux rates. This holds for near-equilibrium as well as for non-equilibrium enzymes. In any case, maximum enzyme activities are significantly higher than maximum metabolic flux rates. Maximum enzyme activities therefore do not permit conclusions on maximum metabolic capacities to be drawn. They may, however, be compared in closely related tissues or different metabolic conditions of a given tissue as relative magnitudes of maximum flux rates. Reference enzymes of constant proportion groups as well as of other enzymes which are representative of distinct metabolic pathways may be used in this sense for the evaluation of enzyme activity patterns. Selection of appropriate enzymes depends on the aim of the intended study, on a thorough knowledge of their individual properties, and on the possibility of measuring their maximum activity under reproducible conditions.

Animals↗
PubMed1979

Microphotometric determination of enzyme activities in cryostat sections by the gel film technique.

Use of the gel film technique in microphotometric determinations of enzyme activity is described. The microscope photometer is computer-controlled. It is programmed to deal with repetitive measurements at up to 12 selected positions within a tissue section and to evaluate recorded reaction rates statistically. Films of polyacrylamide gel with entrapped glucose-6-phosphate dehydrogenase are used as a model to demonstrate the correlation between local enzyme activity and the microphotometrically determined reaction rate. Enzyme activities at different positions in the same tissue section are determined and compared. Activity profiles of five enzymes (glutamate dehydrogenase, lactate dehydrogenase, malate dehydrogenase, succinate dehydrogenase, NAD-dependent tetrazolium reductase) in the liver are presented and show non-uniform intra-acinar distribution patterns. These results are interpreted in the light of the metabolic zonation of the hepatic acinus. Further applications of the method are discussed.

Animals↗
PubMed1979

Principle and method of kinetic microphotometric enzyme activity determination in situ.

An advanced apparative set-up is described for multipositional microphotometric recording of histochemical enzyme reactions in cryostat sections. It consists of a computer controlled microscope photometer with scanning stage. Measurements on the same tissue section may be performed at 12 preselected positions. These are repeatedly brought into the measuring beam in several measuring cycles. The complete measuring process, storage of measuring position coordinates, movements of the stage and statistical evaluation of the data is under computer control. By use of the gel film technique, extinction changes in tetrazolium coupled enzyme reactions can be measured continuously at initial rate conditions. Measurements are performed at identical conditions and can thus be analysed as relative enzyme activities.

Animals↗
PubMed1979

Kinetic microphotometric activity determination in enzyme containing gels and model studies with tissue sections.

The dependence of microphotometrically recorded reaction rate on local enzyme concentration was studied as a basic prerequisite of comparative microphotometric enzyme activity determinations at initial rate conditions in tissue sections. Polyacrylamide gels containing defined concentrations of glucose-6-phosphate dehydrogenase served as a model. Optimal conditions of preparing enzyme containing gels are reported. Measurements in which either thickness of gel sections or enzyme concentration was varied proved the linear relationship between local enzyme concentration and microphotometrically recorded reaction rate. Sections of enzyme containing gels as well as cross-sections of rat muscles were used as models for studying possible influences of heterogeneous chromophore distribution (distributional error). No such influences could be detected during the initial phase of the staining reaction which suggests that distributional error is of no significance for kinetic microphotometric enzyme activity determination at initial rate conditions.

Acrylamides↗
PubMed1979

Microphotometric studies on intraacinar enzyme distribution in rat liver.

Intraacinar distribution of succinate dehydrogenase (SDH), malate dehydrogenase (MDH), NADP-dependent isocitrate dehydrogenase (IDH), glutamate dehydrogenase (GluDH), lactate dehydrogenase (LDH) and NADH-tetrazolium dehydrogenase (TR) was studied in rat liver cryostat sections by multipositional microphotometric activity determinations. By statistical evaluation, activity of individual enzymes could be related to the acinar topography. Activity was evaluated with regard to distance of measuring position either from afferent (portal) or efferent (hepatic) vessels. Two independent distribution curves were obtained for each enzyme. Acinar distribution of all the enzymes studied followed sigmoid courses with maximal activity of SDH, MDH and LDH in zone 1 ("periportal") and GluDH, IDH, TR in zone 3 ("pericentral"). For all enzymes, maximum activity gradients were confined to zone 2 of the acinus. Data were also evaluated as ratios of activities in zone 1 and zone 3. The following ratios zone 1/zone 3 were obtained: SDH = 1.9, MDH = 1.7, IDH = 0.5, GluDH = 0.5, LDH = 1.3 and TR = 0.6.

Animals↗