Biomedical subjects

A L Serrano

Publications and source records attributed to A L Serrano.

At least 19 recordsLinked to original sources

PubMed2003

Sleep disorder in alien hand syndrome.

A 63-year-old right-handed woman developed an alien hand syndrome (AHS) after an acute infarction in the territory of the left anterior cerebral artery. The uncontrolled hand movements were present during the daytime and eventually disturbed sleep. Polysomnography revealed that these motor actions only appeared when the patient was awake. These awakenings emerged mostly from NREM sleep stage 2 during the first half of the night. There was no evidence of any epileptiform activity, dyssomnia or parasomnia. These movements were controlled making her wear an oven mitt during sleep. The temporal distribution of this motor activity seems to follow the progressive hyperpolarization of anterior horn neurons that occurs when sleep deepens. The accommodation of the grasp reflex in AHS probably helps control this unwanted motor activity.

Anterior Horn Cells↗

PubMed2002

Effects of transcutaneous short-term electrical stimulation on M. vastus lateralis characteristics of healthy young men.

Fifteen healthy, untrained male subjects (mean age +/- SD, 22 +/- 5 years) were used to examine the plasticity of myosin heavy chain phenotype, size, oxidative capacity and capillarization of skeletal muscle fibre types with short-term electrical stimulation (ES). Ten subjects were electro-stimulated on both quadriceps muscles with a frequency of 45-60 Hz, with 12 s of stimulation followed by 8 s of recovery for a total of 30 min per day, 3 days per week for 6 weeks. The remaining five subjects served as controls. Two vastus lateralis muscle biopsy samples were removed from each subject before (week 0) and after (week 6) ES training. A standardized exercise test on a cycle ergometer was performed by each subject before and after the experimental period and several indicators of whole-body aerobic capacity were estimated. The so-called electromyographic threshold was also determined during the tests. Muscle biopsy samples were analysed by electrophoresis, immunohistochemistry and quantitative histochemistry. Myosin heavy chain (MHC) composition, muscle fibre type distribution, fibre areas, oxidative capacity and capillaries of each fibre type were estimated. Muscular changes with ES revealed an increase of fibres expressing MHC-IIA, and a decrease of fibres expressing MHC-IIX and MHC-I, as well as an increase of the oxidative capacity and mean number of capillaries of fast-twitch (type II) fibres with minimal muscle fibre hypertrophy. These adaptations seem related to a bi-directional transformation from both MHC isoforms I and IIX towards the MHC-IIA isoform. The aerobic performance and electromyographic variables at the whole-body level were not altered by ES. These results indicate that the particular short-term ES training protocol tested in the present study induces significant adaptations in histochemical and metabolic machineries of human skeletal muscle. The results also offer new perspectives for realistic applications of ES in various clinical situations and sport training.

Adult↗

PubMed2001

Calcineurin controls nerve activity-dependent specification of slow skeletal muscle fibers but not muscle growth.

Nerve activity can induce long-lasting, transcription-dependent changes in skeletal muscle fibers and thus affect muscle growth and fiber-type specificity. Calcineurin signaling has been implicated in the transcriptional regulation of slow muscle fiber genes in culture, but the functional role of calcineurin in vivo has not been unambiguously demonstrated. Here, we report that the up-regulation of slow myosin heavy chain (MyHC) and a MyHC-slow promoter induced by slow motor neurons in regenerating rat soleus muscle is prevented by the calcineurin inhibitors cyclosporin A (CsA), FK506, and the calcineurin inhibitory protein domain from cain/cabin-1. In contrast, calcineurin inhibitors do not block the increase in fiber size induced by nerve activity in regenerating muscle. The activation of MyHC-slow induced by direct electrostimulation of denervated regenerating muscle with a continuous low frequency impulse pattern is blocked by CsA, showing that calcineurin function in muscle fibers and not in motor neurons is responsible for nerve-dependent specification of slow muscle fibers. Calcineurin is also involved in the maintenance of the slow muscle fiber gene program because in the adult soleus muscle, cain causes a switch from MyHC-slow to fast-type MyHC-2X and MyHC-2B gene expression, and the activity of the MyHC-slow promoter is inhibited by CsA and FK506.

Animals↗

PubMed2001

Regulatory elements governing transcription in specialized myofiber subtypes.

Skeletal myofibers of vertebrates acquire specialized metabolic and physiological properties as a consequence of developmental cues in the embryo and different patterns of contractile activity in the adult. The myoglobin gene is regulated stringently in muscle fibers, such that high myoglobin expression is observed in mitochondria-rich, oxidative myofibers (Types I and IIa) compared with glycolytic fibers (Type IIb). Using germ-line transgenesis and somatic cell gene transfer methods, we defined discrete regions of the murine and human genes encoding myoglobin that are sufficient to confer muscle- and fiber type-specific expression to reporter genes. Mutational analysis confirms the importance of A/T-rich, MEF2-binding motifs in myoglobin gene regulation, as suggested by previous studies using different experimental approaches. In addition, we demonstrated a previously unsuspected role for an intragenic E-box motif as a negative regulatory element contributing to the tightly regulated variation in myoglobin gene expression among particular myofiber subtypes.

Animals↗

PubMed2001

Immunolabelling, histochemistry and in situ hybridisation in human skeletal muscle fibres to detect myosin heavy chain expression at the protein and mRNA level.

The distribution of muscle fibres classified on the basis of their content of different myosin heavy chain (MHC) isoforms was analysed in vastus lateralis muscle biopsies of 15 young men (with an average age of 22 y) by correlating immunohistochemistry with specific anti-MHC monoclonal antibodies, myofibrillar ATPase (mATPase) histochemistry and in situ hybridisation with probes specific for MHC beta-slow, MHC-IIA and MHC-IIX. The characterisation of a large number of individual fibres was compared and correlated on a fibre-to-fibre basis. The panel of monoclonal antibodies used in the study allowed classification of human skeletal muscle fibres into 5 categories according to the MHC isoform they express at the protein level, types I, I+IIA, IIA, IIAX and IIX. Hybrid fibres coexpressing two isoforms represented a considerable proportion of the fibre composition (about 14%) and were clearly underestimated by mATPase histochemistry. For a very high percentage of fibres there was a precise correspondence between the MHC protein isoforms and mRNA transcripts. The integrated methods used demonstrate a high degree of precision of the immunohistochemical procedure used for the identification and quantification of human skeletal muscle fibre types. The monoclonal antibody S5-8H2 is particularly useful for identifying hybrid IIAX fibres. This protocol offers new prospects for muscle fibre classification in human experimental studies.

Adult↗

PubMed2001

Coordinated changes of kinematics and muscle fibre properties with prolonged endurance training.

The objective of this study was to investigate the relationship between kinematic variables and muscle characteristics by determining (1) if heavy endurance training alters these variables and (2) if such modifications occur in a coordinated manner. Fifteen Andalusian stallions age 41-45 months were used. Five horses were used as controls and 10 horses underwent a training programme based on aerobic exercise for 8 months. Intensity of exercise was adjusted individually for each horse according to a standardised exercise test. Stride kinematic characteristics at the trot were analysed by videography and gluteus medius muscle biopsies were removed before and after the experiment. Muscle samples were analysed immunohistochemically for fibre types and fibre sizes. After training, stride frequency increased (6%, P < 0.05), whereas stride duration and stance time of the stride decreased (6 and 10% respectively, P < 0.05 in both). The percentage of type IIA fibres increased (25%, P < 0.01), whereas the percentage of type IIX fibres decreased (80%, P < 0.001). Training had no significant effect on the percentage of types IIAX and I fibres. After training, mean lesser fibre diameters of types I and IIA fibres increased (13 and 10%, respectively; P < 0.05). These results suggest that prolonged endurance training alters kinematic and muscle fibre properties in a coordinated manner, reflecting a greater stability and more efficient propulsion associated with an increase in muscle fatigue resistance and strength. This adaptive response has an impact on athletic performance.

Adaptation, Physiological↗

PubMed2000

Early and long-term changes of equine skeletal muscle in response to endurance training and detraining.

Twenty-four 4-year-old Andalusian (Spanish breed) stallions were used to examine the plasticity of myosin heavy chain (MHC) phenotype and the metabolic profile in horse skeletal muscle with long-term endurance-exercise training and detraining. Sixteen horses underwent a training programme based on aerobic exercises for 8 months. Afterwards, they were kept in paddocks for 3 months. The remaining eight horses were used as controls. Three gluteus medius muscle biopsy samples were removed at depths of 20, 40 and 60 mm from each horse before (month 0), during (month 3) and after (month 8) training, and again after 3 months of detraining (month 11). MHC composition was analysed by electrophoresis and immunohistochemistry with anti-MHC monoclonal antibodies. Fibre areas, oxidative capacity and capillaries were studied histochemically. The activities of key muscle enzymes of aerobic (citrate synthase and 3-hydroxy-acyl-CoA-dehydrogenase) and anaerobic (phosphofructokinase and lactic dehydrogenase) metabolism and the intramuscular glycogen and triglyceride contents were also biochemically analysed. Early changes with training (3 months) included hypertrophy of type IIA fibres, a reduction of MHC-IIX with a concomitant increase of MHC-IIA, a rise in the number of high-oxidative fibres and in the activities of aerobic muscle enzymes and glycogen content. Long-term changes with training (8 months) were a further decline in the expression of MHC-IIX, an increase of slow MHC-I, additional increases of high-oxidative fibres, capillary density, activities of aerobic enzymes and endogenous glycogen; intramuscular lipid deposits also increased after 8 months of training whereas the activities of anaerobic enzymes declined. Most of exercise-induced alterations reverted after 3 months of detraining. These results indicate that endurance-exercise training induces a reversible transition of MHC composition in equine muscle in the order IIX-->IIA-->I, which is coordinated with changes in the metabolic properties of the muscle. Furthermore, a dose-response relationship was evident between the duration (in total) of training and the magnitude of muscle adaptations.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed2000

Myosin heavy chain profile of equine gluteus medius muscle following prolonged draught-exercise training and detraining.

Fourteen 4-year old Andalusian mares were used to examine the plasticity of myosin heavy chain (MHC) composition in horse skeletal muscle with heavy draught-exercise training and detraining. Seven horses underwent a training programme based on carriage exercises for 8 months. Afterwards, they were kept in paddocks for 3 months. The remaining seven animals were used as control horses. Three gluteus medius muscle biopsies were removed at depths of 20, 40 and 60 mm from each horse before (month 0), during the training (months 3 and 8) and after detraining (month 11). Myosin heavy chain composition was analysed by electrophoresis and immunohistochemically with anti-MHC monoclonal antibodies. Fibre areas, oxidative capacity and capillaries were studied histochemically. After 8 months of training, MHC-IIX and IIX fibres decreased whereas MHC-I and type I and I + IIA fibres increased. Neither MHC-IIA nor the percentage of IIA fibres changed when the data were considered as a whole, but the proportion of MHC-IIA increased in the superficial region of the muscle after 8 months of training. Mean areas of type II fibres were not affected by training and detraining, but the cross-sectional of type I fibres increased after 3 month of training and not further increases were recorded afterward. The percentage of high-oxidative capacity fibres and the number of capillaries per mm2 increased with training. Most of these muscular adaptations reverted after detraining. These results indicate that long term draught-exercise training induces a reversible transition of MHC composition in equine muscle in the order IIX --> IIA --> I. The physiological implication of these changes is an impact on the velocity of shortening and fatigue resistance of muscle fibres.

Animals↗

PubMed2000

Ras is involved in nerve-activity-dependent regulation of muscle genes.

Gene expression in skeletal muscle is regulated by the firing pattern of motor neurons, but the signalling systems involved in excitation-transcription coupling are unknown. Here, using in vivo transfection in regenerating muscle, we show that constitutively active Ras and a Ras mutant that selectively activates the MAPK(ERK) pathway are able to mimic the effects of slow motor neurons on expression of myosin genes. Conversely, the effect of slow motor neurons is inhibited by a dominant-negative Ras mutant. MAPK(ERK) activity is increased by innervation and by low-frequency electrical stimulation. These results indicate that Ras-MAPK signalling is involved in promoting nerve-activity-dependent differentiation of slow muscle fibres in vivo.

Amino Acid Substitution↗

PubMed1999

How is muscle phenotype controlled by nerve activity?

Motor neurons are known to affect muscle growth and fiber type profile (fast/slow, oxidative/glycolytic) by regulating muscle gene expression. However, the mechanism by which the information contained in specific action potential patterns is decoded by the transcriptional machinery of muscle fiber nuclei remains to be established. This is a basic issue in nerve/muscle biology, which has major implications in neurology, sport medicine and aging. We describe here a general strategy aimed at identifying the signal transduction pathways mediating the effects of nerve activity. This approach is based on the overexpression of constitutively active or dominant negative transduction factors in regenerating skeletal muscle.

Action Potentials↗

PubMed1999

Analysis of myosin heavy chains at the protein level in horse skeletal muscle.

Combined methodologies of enzyme-linked immunosorbent assay (ELISA), sodium dodecyl sulphate polyacrilamide gel electrophoresis (SDS-PAGE), immunoblotting, traditional myofibrillar ATPase (mATPase) histochemistry and immunocytochemistry of whole biopsied samples were used to study myosin heavy chain (MHC) isoforms in the equine gluteus medius muscle. The ELISA technique allowed the quantification of the three MHC isoforms known to be present in different horse muscles: slow (MHC-I) and two fast (termed MHC-IIA and MCH-IIX). The SDS-PAGE method resolved MHCs in three bands: MHC-I, MHC-IIX and MHC-IIA from the fastest to the slowest migrating band and a quantification by densitometry for each MHC isoform was also possible. The identity of these three MHCs was confirmed by immunoblots with specific monoclonal antibodies. Five fibre types were defined immunohistochemically according to their MHC content: I, I + IIA, IIA, the hybrid IIAX and IIX. When quantitative data obtained with the four different methodologies were combined and compared, they were consistent and, when considered together, showed significant correlation. Nevertheless, the percentage of MHC-IIA histochemically derived was underestimated, while that of MHC-IIX was overestimated in comparison with the immunocytochemical determination of these MHC isoforms. The percentage of MHC-I obtained by ELISA technique was underestimated. In short, these integrated methods for the analysis of MHCs at the protein level demonstrate that equine skeletal muscle does not express the MHC-IIB, so type II fibres have been misclassified in numerous previous studies based upon the vary traditional mATPase histochemistry. They also offer new prospects for muscle fibre typing in equine experimental studies and veterinary medicine.

Animals↗

PubMed1999

Distribution of fast myosin heavy chain-based muscle fibres in the gluteus medius of untrained horses: mismatch between antigenic and ATPase determinants.

The distribution of muscle fibres classified on the basis of their content of different myosin heavy chain (MHC) isoforms was analysed in muscle biopsies from the gluteus medius of adult untrained horses by correlating immunohistochemistry with specific anti-MHC monoclonal antibodies and standard myofibrillar ATPase (mATPase) histochemistry. Percutaneous needle biopsies were taken at 3 depths (20, 40 and 60 mm) from 4 4-y-old Andalusian stallions. The percentage of 'pure' I MHC fibres increased whereas that for pure IIX MHC fibres decreased from the most superficial to the deepest sampling site. Within the fast fibres, types IIA and IIAX MHC-classified fibres were proportionately more abundant in the deepest sampling site than in the superficial region of the muscle. The immunohistochemical and histochemical characterisation of a large number of single fibres (n = 1375) was compared and correlated on a fibre-to-fibre basis. The results showed that 40% of the fibres analysed were pure type I (expressing only MHC-I); they showed correct matching between their antigenic and mATPase determinants. In contrast, within the fast fibres, a considerable proportion of fibres were found showing a mismatch between their immunohistochemical and mATPase profiles. The most common mismatched fibre phenotypes comprised fibres displaying coexpression of both fast MHCs when analysed by immunocytochemistry, but showing an mATPase profile similar to typical IIX fibres (moderate mATPase reaction after preincubation at pH 4.4). Considered altogether, the total mismatched fibres represented only 4.2% of the whole fast fibre population in the superficial region of the muscle, but their proportion increased to 15.6% and 38.4% in the middle and deep regions, respectively, of gluteus medius. It is concluded that a considerable number of hybrid fast MHC IIAX fibres are present in the gluteus medius of untrained horses, suggesting that equine type II fibres have probably been misclassified in numerous previous publications based on the use of histochemistry alone. This has important implications in attempts to study the physiological properties of fast fibre types adequately in horses.

Animals↗

PubMed1999

Skeletal myosin heavy chain composition and carriage training.

Three different myosin heavy chain (MHC) isoforms have been identified in the equine gluteus medius muscle: the slow or MHC-I and the 2 fast MHC-IIA and MHC-IIX isoforms. They are distributed in 3 fibre types containing a single MHC (I, IIA, IIX) and 2 hybrid types co-expressing 2 isoforms (I + IIA, IIA + IIX). The aim of this study was to determine if heavy carriage training alters skeletal MHC composition in horses. Fourteen Andalusian mares age 42-46 months were used. Seven horses were used as controls to estimate the effects of growth on muscle. The remaining 7 horses underwent a training programme based on carriage exercise for 8 months. The intensity of exercise was individually adjusted to each horse according to a standardised exercise test. Gluteus medius muscle biopsies were analysed biochemically for MHC composition by electrophoresis, immunohistochemically for fibre types with specific anti-MHC monoclonal antibodies, and histochemically for fibre type areas, fibre oxidative capacity and capillaries. After training, MHC-IIX decreased and MHC-I increased. The percentages of type IIX and IIAX (i.e. fibres co-expressing MHCs IIA and IIX) fibres decreased, whereas the percentage of type I fibres increased. Neither MHC-IIA composition nor type IIA fibre percentage changed with training. The training had no significant effect on fibre areas and capillaries, but the percentage of fibres with high oxidative capacity increased. The control group showed no changes in muscle variables after the 8 month training period. These results suggest that carriage training alters MHC composition in equine skeletal muscle, reflecting a conversion of MHC isoforms in the order IIX-->IIA-->I and suggesting a reduction in the velocity of shortening of the muscle, but an increase in fatigue resistance.

Animals↗

PubMed1998

Neural regulation of myosin gene expression in regenerating skeletal muscle.

Excitation-transcription coupling, namely the process whereby plasma membrane depolarization leads to gene activation or inactivation, is still a black box for most muscle genes. Muscle regeneration is a useful model system to ask basic questions concerning the triggering signals and the transduction pathways involved in activity-dependent gene regulation. We report ongoing research in our laboratory concerning (1) myosin heavy chain changes in regenerating muscle in the presence and absence of the nerve, as well as changes induced by electrical stimulation, (2) identification of activity response elements in the promoter of a slow myosin light chain gene, and (3) potential approaches to define the transduction pathways induced by neural or electrical activity and implicated in muscle gene regulation.

Animals↗

PubMed1996

Myosin isoforms and muscle fiber characteristics in equine gluteus medius muscle.

BACKGROUND: To date, four different myosin heavy chain (MyHC) isoforms have been identified in adult skeletal muscle of a number of species: types I, IIa, IIx or IId, and IIb. The aim of this study was to investigate the distribution of various MyHC isoforms in the equine gluteus medius and gluteus profundus muscles in relation with several morphometric variables of muscle fibers. METHODS: Samples from different depths of the gluteus medius muscle (2, 4, 6, and 8 cm) and gluteus profundus muscle of five sedentary horses were examined by MyHC gel electrophoresis, monoclonal antibodies staining against fast, slow and neonatal MyHC isoforms, myosin adenosine triphosphatase (m-ATPase) activity, nicotinamide adenine dinucleotide tetrazolium reductase, alpha-glycerophosphate dehydrogenase, and alpha-amylase-PAS. Data about relative frequencies, sizes, and capillaries of the various histochemical fiber types were collected by morphometry. RESULTS: Three MyHC isoforms were present in the gluteus medius muscle. Two of them comigrated with type I and IIa MyHC isoforms of rat diaphragm (used as a control). The third isoform showed an electrophoretic mobility closer to type IIx than to the IIb MyHC isoform of rat diaphragm. Only two MyHC isoforms (type I and IIa) were detected in the gluteus profundus muscle. In both muscles, type I fibers (high m-ATPase activity at pH 4.5) only reacted with the anti slow-MyHC antibody and both type IIA and IIB fibers (low and moderate m-ATPase activity at pH 4.5, respectively) only reacted with the anti fast-MyHC antibody. No cross-reactivity of fibers positive for both antibodies was found except for the scarce type IIC fibers. Fiber types and capillaries were heterogeneously distributed across the gluteus medius muscle. The deeper regions of this muscle were found to contain a higher percentage of type I fibers, a large number of capillaries and a lower proportion of type IIB fibers compared to the superficial regions of the muscle. The gluteus profundus muscle had more abundant and larger type I fibers than the deepest sampling site of the gluteus medius muscle. CONCLUSIONS: These results show the existence of three different MyHC isoforms in the equine gluteus medius muscle and that fiber types and MyHC isoforms are heterogeneously distributed within this muscle. The distribution of slow-twitch and fast-twitch MyHCs among the fibers determined by immunohistochemistry was in agreement with histochemically identified type I and type II fibers, respectively.

Adenosine Triphosphatases↗

PubMed1996

[Electrical status epilepticus during sleep].

INTRODUCTION: Sleep electrical status epilepticus (SESE) is a rare entity whose diagnosis depends or showing spike and wave complexes on the EEG during more than 85% of the duration of NoREM sleep. Typically it presents in children, most of whom have subjacent epilepsy. It is currently accepted that SESE is asymptomatic, although its persistence may give rise to severe neuropsychological sequelae. There are no references to sleep disorders in these patients. We present the case of a seven year old girl with SESE, hypersomnia and secondary nocturnal enuresis. CLINICAL CASE: The seven year old patient had a past history of simple partial crises with motor symptoms. There was progressive hypersomnia and nocturnal enuresis. The polysomnogram showed SESE. The Test for Multiple Latencies in Sleep (TMLS) showed pathological diurnal somnolence. HLA DR2 typing was negative. Neuropsychological study showed severe alterations in the language area, with a normal intelligence quotient. CONCLUSIONS: The new findings presented suggested that SESE is an intrinsic sleep disorder and not merely an EEG pattern. Since it occurs in children, sometimes with neuropsychological deficits, systematic TMLS should be done. The association of hypersomnia, changes in immediate visual memory and autistic regression suggest involvement of the limbic system.

Brain↗

PubMed1995

Activities of selected aerobic and anaerobic enzymes in the gluteus medius muscle of endurance horses with different performance records.

Biopsies of the gluteus medius muscle were taken at three different depths from 36 endurance horses aged 8.42 +/- 2.85 years and of both sexes. Twenty of the horses were considered to be excellent performers on the basis of the mean speed of their three fastest records in endurance events over the previous two or three years, whereas 16 were moderate performers. The biopsy samples were analysed for the activities of the enzymes citrate synthase (an indicator of citric acid cycle activity), 3-OH-acyl-CoA-dehydrogenase (an indicator of lipid oxidation) and lactate dehydrogenase (an indicator of anaerobic metabolism). The 20 excellent performers had higher activities of citrate synthase (P < 0.001) and 3-OH-acyl-CoA-dehydrogenase (P < 0.02) than the 16 moderate performers. The activities of citrate synthase and 3-OH-acyl-CoA-dehydrogenase increased by 65 per cent and 75 per cent, respectively, and the activity of lactate dehydrogenase decreased by 23 per cent in the samples taken at successively greater depths. There was a strong linear relationship between the ratios of the activities of lactate dehydrogenase/citrate synthase and lactate dehydrogenase/3-OH-acyl-CoA-dehydrogenase and the depth from which the samples were taken for both performance groups (P < 0.001). The intercepts of the regression lines were higher in the moderate than in the excellent performers (P < 0.001 and P < 0.01 for the two ratios), showing that the endurance horses with the better performance record had a greater aerobic capacity and a relatively lower anaerobic capacity in the gluteus medius muscle than the horses with a poorer record.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1995

Effects of a 3 month endurance training programme on skeletal muscle histochemistry in Andalusian, Arabian and Anglo-Arabian horses.

Twenty adult (5 to 14 years old) sedentary stallions of several breeds (8 Andalusians, 7 Arabians and 5 Anglo-Arabians) were endurance-trained for 3 months. Duplicate biopsies from 2 different depths (20 mm, superficial sampling site; 60 mm, deep sampling site) of the gluteus medius muscle were collected before and after training and after 3 months of detraining. Few significant changes in muscle fibre type composition were recorded in response to training. The percentage of type I fibres in the deep sampling site of the muscle in Andalusian horses and of type IIB oxidative fibres in the superficial region in Anglo-Arabians had increased significantly (P < 0.05) after training. The mean type I and IIA cross-sectional area was increased significantly (range P < 0.05 to P < 0.01) after 3 months' training in the deep site of the muscle in Arabian and Andalusian horses, but not in Anglo-Arabians. The changes seen in fibre sizes disappeared after the detraining period. The mean number of capillaries adjacent to type I fibres in the superficial sampling site of the muscle had increased significantly (P < 0.05) in response to training in Andalusian and Arabian horses. However, a significant decrease in the mean number of capillaries in contact with each fibre type relative to the mean area of that fibre type was observed associated with training in the deep region of the muscle for type I and IIA fibres in Arabians (P < 0.01) and for type I fibres in Andalusian horses (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗