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Biomedical subjects

A Veicsteinas

Publications and source records attributed to A Veicsteinas.

68 records · Page 4Linked to original sources
PubMed1978

Morphologic and metabolic studies in a case of oculo-cranio-somatic neuromuscular disease.

A case resembling the syndrome of "ophthalmoplegia plus" or "oculo-cranio-somatic neuromuscular disease" is reported. A biopsy of deltoid muscle showed that 23% of the fibers were "ragged-red fibers" and were all type 1. Study of their ultrastructure revealed clusters of abnormal skeletal muscle mitochondria in subsarcolemmal and intermyofibrillar spaces. A liver biopsy also revealed a considerable increase in the number and size of the mitochondria. In some instances the mitochondria contained osmiophilic rounded inclusions surrounded by myelin-like structures. Metabolic studies revealed an increase of blood lactate concentration after very light exercise, while the O2 consumption was increased within the expected range. It is concluded that: a) the association of ophthalmoplegia and ultrastructural alterations of the mitochondria in muscle fibers may represent a specific nosographic entity: b) mitochondrial abnormalities are not limited to the skeletal muscles and c) the dysmetabolic basis of such a clinico-pathological entity might lie in an alteration of the mechanism which regulates the mitochondrial oxidative phosphorylation.

Adult↗
PubMed1976

Pulmonary O2 diffusing capacity at exercise by a modified rebreathing method.

The rebreathing technique for the measurement of the pulmonary O2 diffusing capacity, DO2, previously developed for resting conditions [Cerretelli et al., J. appl. Physiol. 37, 526-532 (1974)] has been modified for application to exercise and simplified to one rebreathing maneuver only. The changes consist: 1) in administering in the course of a normoxic exercise a priming breath of an O2 free mixture just before the onset of rebreathing in order to achieve rapidly the appropriate starting PO2 values on the linear part of the O2 dissociation curve as required by the method; 2) in calculating mixed venous blood O2 tension by extrapolation of the alveolar to mixed venous blood PO2 equilibration curve, instead of determining it separately. While the mean DO2 value of 21 measurements on 5 subjects at rest was 30 ml-min-1 - Torr-1 +/- 3 (S.E.), in 2 subjects exercising on a bicycle ergometer, DO2 was found to increase from a resting value of about 32 ml- min-1 - Torr-1 to 107 ml - min-1 - Torr-1 for an eightfold increase of O2 uptake. The validity and the applicability of the method are critically discussed.

Humans↗
PubMed1976

Energetics of isometric exercise in man.

In isometric contractions of the plantar flexors (5-40% of maximal tension, Tmax), VO2 is linearly related to the force exerted, averaging 2 ml/min-kg of tension. At tension levels above 5% Tmax the lactic acid contribution to the overall energy demand is constant at about 20%. Therefore, up to at least 40% Tmax,-muscle blood flow is not totally occluded, though it is impaired even at low force levels. Below 5% Tmax no lactic acid (LA) accumulates in blood. The energy required for the development of the tension is linearly related to the force exerted up to 33% Tmax, thereafter increasing disproportionately. In the transition from rest to static contractions of the plantar and forearm flexors (30 and 40% Tmax, respectively) VO2 increases initially to 200% of the controls, leveling off later at 150%. During recovery, VO2 increases up to 200% of the initial resting level, due to the payment of a large O2 debt, decreasing then with a t 1/2 of about 30 s. The glycolytic component is relatively more important in isometric contractions of the forearm than of the plantar flexors. No LA accumulates in static contractions of the plantar flexors of 5-10 s duration interrupted by equal pauses.

Adult↗
PubMedDate not supplied

Muscle surface mechanical and electrical activities in myotonic dystrophy.

The dimensional changes of the muscle fibres of the active motor units generate a signal, labelled as mechanomyogram (MMG), related to the number and firing rate of the active fibres. Aim of the study was to evaluate if the root mean square (RMS) of the surface EMG, of the MMG and their relationship (electromechanical coupling efficiency, EMCE) are related to the clinical stage of patients affected by myotonic dystrophy. The EMG and the MMG were recorded during isometric contractions at 20%, 40% and 60% of the maximal voluntary contraction (MVC), in less (elbow flexors, EF) and more (finger flexors, FF) affected muscles in 10 myotonic dystrophy (DM) patients (duration of disease: 15-22 yr.; MDRS scale: 3-4) and in 10 age matched controls (C). It resulted that I) the MVC was only 30% lower in DM than in C (P > 0.05) for the EF but 74% lower (P < 0.001) for the FF; II) at the same relative force the MMG-RMS and the EMG-RMS in DM were significantly lower than in C (P < 0.05); III) the EMCE was almost the same in DM and C for EF but dramatically lower for FF. In conclusion these findings provide evidence that the EMCE changes due to the dystrophic process can be monitored by this new and non invasive technique. A good concurrence of clinical findings and experimental results was observed.

Adult↗