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Biomedical subjects

G Ferretti

Publications and source records attributed to G Ferretti.

At least 163 records · Page 9Linked to original sources
PubMed1995

Loss of muscle oxidative capacity after an extreme endurance run: the Paris-Dakar foot-race.

We measured changes in maximal oxygen uptake capacity (VO2max), ventilation, heart rate, plasma lactate and speed at the end of an incremental exercise test as a consequence of a relay foot race from Paris to Dakar in 6 subjects. Additionally, anthropometric measurements were taken and muscle biopsies from M. vastus lateralis were obtained before and after the race. The latter were analyzed with morphometric methods for fiber size, capillarity and muscle ultrastructural composition. Weight specific VO2max was significantly reduced from 62.4 to 60.5 ml/min.kg after the race while absolute VO2max and the other endurance related functional variables remained unchanged. Body fat, thigh cross-sectional area and thigh volume showed tendential reduction immediately after the race but regained pre-race values within a few days. Fiber size and capillarity were not affected by the race. Volume density of total mitochondria was significantly reduced from 6.98 to 4.89% of fiber volume. Both subsarcolemmal and interfibrillar mitochondria were significantly reduced by 59 and 21%, respectively. The volume density of satellite cell was increased about three-fold whereas the content of lipofuscin remained constant. It is concluded that extreme endurance events such as a multi-stage relay race may induce a considerable loss of oxidative capacity of skeletal muscle tissue.

Adipose Tissue↗
PubMed1995

Successful stenting of a pulmonary arterial stenosis after a single lung transplant.

A 44 year old patient with end stage idiopathic pulmonary fibrosis underwent single left lung transplantation. A perfusion lung scan performed 13 days after transplantation revealed deficient perfusion in the transplanted lung. Pulmonary angiography showed severe pulmonary artery anastomotic stenosis. Percutaneous insertion of a balloon expandable stent improved both pulmonary perfusion and respiratory function.

Adult↗
PubMed1995

Benign noninflammatory bronchial stenosis: treatment with balloon dilation.

PURPOSE: To assess the efficacy of balloon dilation in the treatment of acquired, noninflammatory bronchial stenosis of benign origin. MATERIALS AND METHODS: Balloon bronchoplasty was performed with fluoroscopic guidance 36 times in 19 bronchial stenoses in 16 consecutive patients, with use of a local anesthetic. RESULTS: Initial technical success was attained in all cases; clinical success was achieved in 13 (68%) of 19 bronchial stenoses. Six of the 19 stenoses were dilated unsuccessfully because they were caused by localized bronchomalacias. Of these initial successes, seven stenoses recurred but were redilated with success in four cases. At a mean follow-up of 21.6 months (range, 7-60 months), improvement in both fiberoptic bronchoscopy and respiratory status was seen in nine (69%) of 13 patients with fibrous stenoses. CONCLUSION: Balloon bronchial dilation can be proposed as the primary treatment in acquired, noninflammatory bronchial stenoses of various benign origins including stenoses after lung transplantation.

Adolescent↗
PubMed1995

Maximal exercise performance in chronic hypoxia and acute normoxia in high-altitude natives.

Maximal O2 uptake (VO2max) was determined on a bicycle ergometer in chronic hypoxia (CH) and during acute exposure to normoxia (AN) in 50 healthy young men who were born and had lived at 3,600 m altitude (La Paz, Bolivia). VO2max was significantly improved (approximately 8%) by AN. However, the difference in VO2max measured in CH and AN (delta VO2max) was lower than that reported in sea-level natives (SN) who exercised in chronic normoxia and acute hypoxia. It is shown that high-altitude natives (HN) and SN have a similar VO2max in normoxia, but highlanders can attain a greater VO2max when O2 availability is reduced by altitude exposure. In addition, in HN, the higher the subject's VO2max in hypoxia, the smaller his delta VO2max. These results contrast with the data obtained in 14 lowlanders acclimatized to high altitude who showed that their delta VO2max was positively related to their VO2max in hypoxia, as previously reported in SN who exercised in acute hypoxia (A. J. Young, A. Cymerman, and R. L. Burse. Eur. J. Appl. Physiol. Occup. Physiol. 54: 12-15, 1985). Furthermore, arterial O2 saturation of HN behaved differently from acclimatized lowland natives, inasmuch as it fell less during exercise both in CH and AN. HN with high aerobic capacity display a lower exercise ventilation and a reduced arterial saturation, which could explain their inability to improve VO2max with normoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1995

Training in hypoxia vs. training in normoxia in high-altitude natives.

To determine the interactions between endurance training and hypoxia on maximal exercise performance, we performed a study on sedentary high-altitude natives who were trained in normoxia at the same relative (n = 10) or at the same absolute (n = 10) intensity of work as hypoxia-trained subjects (n = 10). The training-induced improvement of maximal oxygen uptake (VO2max) in hypoxia-trained subjects was similar to that obtained in normoxia-trained sea-level natives submitted to the same training protocol (H. Hoppeler, H. Howald, K. Conley, S. L. Lindstedt, H. Claassen, P. Vock, and E. W. Weibel. J. Appl. Physiol. 59: 320-327, 1985). Training at the same absolute work intensity in the presence of increased oxygen delivery failed to provide a further increase in VO2max. VO2max was not improved to a greater extent by simultaneously increasing absolute work intensity and O2 delivery during the training sessions. In addition, training in normoxia is accompanied by an increased blood lactate accumulation during maximal exercise, leading to greater drops in arterial pH, bicarbonate concentration, and base excess. We conclude that, in high-altitude natives, 1) training at altitude does not provide any advantage over training at sea level for maximal aerobic capacity, whether assessed in chronic hypoxia or in acute normoxia; 2) VO2max improvement with training cannot be further enhanced by increasing O2 availability alone or in combination with an increased work intensity during the exercising sessions; and 3) training in normoxia in these subjects results in a reduced buffer capacity.

Adult↗
PubMed1995

Maximal rate of blood lactate accumulation during exercise at altitude in humans.

The lower peak lactate accumulation in blood ([La(b)]p) at altitude may be associated with a reduced maximal glycolytic flux. Based on certain assumptions, the latter can be indirectly evaluated in vivo, during short supramaximal exercises, by measuring the maximal rate of lactate accumulation in blood (delta [La(b)]max). delta [La(b)]max was determined on six white subjects at sea level (SL1), after approximately 1 wk (Alt1) and 4 wk (Alt2) of a 35-day sojourn at 5,050 m, and 1 wk after return to sea level (SL2). The subjects performed exercises of increasing duration (5, 15, 25, 35, 45 s or until exhaustion) on a bicycle ergometer at loads = 200% of the individual Wmax. The latter was previously determined in each condition as the greatest work rate that could be sustained for 2-4 min during an incremental exercise. Net [La(b)] accumulation (delta [La(b)]) was measured after each exercise bout. delta [La(b)] resulted to be linearly related to exercise duration. The slopes of the individual delta [La(b)] vs. exercise duration lines were taken as delta [La(b)]max. Exhaustion times were approximately 30-45 s in all conditions. [La(b)]p (in mM) during recovery after the exhaustive load was higher at SL1 (10.22 +/- 1.09; means +/- SD) than at Alt1 (5.08 +/- 0.82), Alt2 (8.13 +/- 2.67), and SL2 (8.18 +/- 1.43). delta [La(b)]max was lower at Alt1 (0.09 +/- 0.02) and at Alt2 (0.17 +/- 0.05) than at SL1 (0.25 +/- 0.05) and SL2 (0.23 +/- 0.06). Both [La(b)]p and delta [La(b)]max increased during acclimatization.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1995

Human intramuscular temperature and heat flow transients at rest.

A general model for heat exchange, comprising the major models in the literature, was developed. Temperature changes as a function of space and time were determined in six resting humans (age 32.7 +/- 4.5 yr) during temperature transients by magnetic resonance imaging (MRI), so that the exact solution of the model was obtained. These results allowed application of the model, e.g., the analysis of transient muscle heat flow changes, which could not be assessed by previous steady-state analyses. A microthermocouple was inserted in muscle vastus lateralis 2-3 cm below the skin surface. The measured temperature was used for calibrating the pixel intensity of a temporal series of transaxial magnetic resonance images obtained with a spin echo sequence around the microthermocouple position. After muscle temperature was increased by immersion in a controlled water bath, MRI acquisition was performed while muscle temperature was decreasing. Temperature maps relative to space and time inside a homogeneous region of interest were reconstructed by neural networks, showing specific temperature patterns. Subsequently calculated heat flows (with negative sign) appeared to increase linearly as temperature decreased, until a maximum was attained at a critical temperature, below which dramatic consistent heat flow changes were found. In conclusion, MRI is indeed a powerful technique, useful to study the determinants of muscle temperature and heat flow changes in space and time.

Adult↗
PubMed1995

[Upper airways and sleep apnea syndrome].

The imaging techniques of the upper airway (UA) now permit a description of the characteristics of pharyngeal collapse during the course of obstructive apnoea. The start is oropharyngeal with active movements anterior and posterior of the soft palate and a falling back of the tongue. The extension occurs almost systematically towards the hypopharynx. A displacement of the hyoid bone and of the cervical spine is noted synchronously with thoracoabdominal movements. These imaging techniques of UA show the occurrence of passive pharyngeal collapse during certain types of central apnoea. In snorers and in apnoeics, there is a reduction of the calibre of the pharynx. However, these abnormalities are not specific and do not enable the diagnosis to be confirmed nor an estimate of the severity of the sleep apnoea syndrome. Cephalometry and computed tomography of the pharynx should be carried out particularly when a uvulopalatopharyngoplasty (UPPP) is envisaged. For practical purposes, the existence on cephalometry of retrognathism with an MP-H > 24 mm and a PAS distance of < 5 mm is associated with a poor result for UPPP. The same thing applies when macroglossia or a reduction of the surface of the hypopharynx is found on computed tomography.

Adult↗
PubMed1995

[Left ventricular insertion of a permanent pacemaker (radiographic aspect)].

We report a case of inadvertent transarterial permanent pacing of the left ventricule that was not diagnosed on routine chest radiography or ECG. The malposition was diagnosed because of the rupture of the mitral valve cordage 2 months after pacemaker implantation. We emphasize the radiographic appearance of this rare malposition.

Cardiac Pacing, Artificial↗
PubMed1995

[Progress in tomodensitometry. Applications in cancerology].

Since 1992, spiral CT scanners replace conventional CT units in radiology departments. In the first part of this paper, we present some technical considerations concerning spiral CT (continuous rotation and emission of the source-detector; continuous translation of the patient at a constant rate through the gantry), as well as advantages and limitations of volumic acquisition. The main advantages can be summerized as: reduction of the acquisition time, optimization of contrast enhancement with intravenous opacification, and post processing allowing retrospective creation of overlapping images, multiplanar reconstructions, and 3-D reconstructions. Spiral CT improves lesions detection and characterization. Disadvantages are due to contrast media injection and radiation exposure. Then we describe clinical applications in the carcinologic field concerning pharyngo-laryngeal tumors, bronchogenic carcinoma, mediastinal tumors, pulmonary nodules, sub-diaphragmatic tumors. However, tumors of brain, spine, bone, and soft tissue are better explorated with MRI. Authors conclude on the future improvements of spiral CT.

Adult↗
PubMed1994

Is interhemispheric transfer time related to age? A developmental study.

In simple visuomotor reaction time tasks, the difference between reaction time (RT) in the uncrossed hand/hemifield condition from RT in the crossed hand/hemifield, known as CUD (crossed-uncrossed difference), has been interpreted as reflecting interhemispheric transmission time (IHTT). Several studies in normal adults have found a CUD of a few milliseconds (3-4), while an abnormally long CUD has been reported in patients who underwent a surgical section of the corpus callosum or in congenital acallosal subjects. The corpus callosum, which is the most important structure for interhemispheric transfer of information, completes its myelination approximately by age ten. It has been hypothesized that the functional maturity of the corpus callosum coincides with the termination of the myelination cycle. No developmental study has focused on the development of IHTT, in relation to callosal maturation. The purpose of our study has been to investigate the development of interhemispheric transfer of visuomotor information in children aged seven to eleven, using a simple RT task with lateralized visual stimuli. The results indicate an age-related decrease of CUD, which we interpret as reflecting the maturation of the corpus callosum during childhood years.

Cerebral Cortex↗
PubMed1994

Hard metal lung disorders: analysis of a group of exposed workers.

The experience gained during the last 5 years in the study of 36 male workers exposed to hard metal dusts (10 engaged in mixing, 12 in presintering, three in sintering and 11 in grinding) is presented. The mean age was 33.2 years (S.D., 11.8) and the mean number of years of exposure was 9.4 (S.D., 7.6). All subjects received a physical examination, chest X-rays, pulmonary function test (VC, FEV1, expiratory flows, RV, DLCO, and metacholine bronchial provocation test), skin tests, bronchoalveolar lavage (BAL) and determination of trace metals in BAL, blood, urine, pubic hair and toe nails. Two cases of bronchial asthma, six cases of interstitial lung disease and one case with both disorders were identified; eight of these cases presented at BAL signs of alveolitis with different cytologic features. Among the other 27 asymptomatic subjects, two showed an aspecific bronchial hyperreactivity, four showed a reduced DLCO, 12 showed an inverted ratio of CD4/CD8 lymphocytes in BAL without signs of alveolitis while one subject presented both an aspecific bronchial reactivity and a reduced DLCO. The presence of aspecific bronchial hyperreactivity in asymptomatic subjects might represent a preclinical indicator of a possible evolution towards bronchial asthma. An altered DLCO, alone or associated with an inverted CD4/CD8 ratio of BAL lymphocytes, might constitute an early sign of a possible evolution towards interstitial lung disease. The association of aspecific bronchial reactivity and reduced DLCO might indicate the possible evolution towards a mixed form.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Standardisation of 31phosphorus-nuclear magnetic resonance spectroscopy determinations of high energy phosphates in humans.

A procedure is described for standardising the determination of adenosine 5'-triphosphate and phosphocreatine concentration ([ATP] and [PC], respectively, in absolute arbitrary units) in human muscle by nuclear magnetic resonance (NMR) spectroscopy. The individual 31phosphorus (31P)-NMR spectra obtained on equal hemispherical tissue volumes (muscle plus skin and fat) were corrected for the thickness of the skin and of the subcutaneous fat. The volumes investigated were standardised using an external reference. The procedure described made possible the comparison of high energy phosphate concentrations among different subjects. It was applied to the assessment of [ATP] and [PC] in four groups of sedentary subjects (children, and adults aged 20-35, 35-50 and over 50 years), and in a group of athletes (volleyball players). The [ATP] and [PC] were not statistically different in the groups investigated.

Adenosine Triphosphate↗
PubMed1994

Determinants of peak muscle power: effects of age and physical conditioning.

The relationships between absolute peak muscle power (Wpeak), muscle cross sectional area (CSAtot, i.e. the sum of both thigh and calf CSA) and muscle high energy phosphate concentration (adenosine 5'-triphosphate [ATP] and phosphocreatine concentrations [PC]) were studied in 47 subjects classified into five groups: A, 10 sedentary (S) subjects aged 20-35 years; B, 9 S aged 35-50 years; C, 9 S aged more than 50 years; D, 13 children aged 8-13 years; and E, 6 athletes (top level volleyball players) aged 24 (SD 3) years. The Wpeak was measured during a maximal vertical high jump off both feet on a force platform. The CSAtot was measured anthropometrically. The [ATP] and [PC] were determined by 31Phosphorus nuclear magnetic resonance spectroscopy. The Wpeak decreased with age, was 65% lower in D than in A, and 43% higher in E than in A. The CSAtot did not vary with age, was 45% smaller in D than in A, and 15% greater in E than in A. The [ATP] and [PC] were essentially the same in all groups. The changes observed in Wpeak were only partially accounted for by changes in CSAtot. Therefore, in addition to the variables investigated, other factors appear to have been involved in the determination of Wpeak with increasing age and training. An important role may be played by hormonal, particularly at puberty, and neural factors.

Adenosine Triphosphate↗
PubMed1994

Pygmy locomotion.

The hypothesis that Pygmies may differ from Caucasians in some aspects of the mechanics of locomotion was tested. A total of 13 Pygmies and 7 Caucasians were asked to walk and run on a treadmill at 4-12 km.h-1. Simultaneous metabolic measurements and three-dimensional motion analysis were performed allowing the energy expenditure and the mechanical external and internal work to be calculated. In Pygmies the metabolic energy cost was higher during walking at all speeds (P < 0.05), but tended to be lower during running (NS). The stride frequency and the internal mechanical work were higher for Pygmies at all walking (P < 0.05) and running (NS) speeds although the external mechanical work was similar. The total mechanical work for Pygmies was higher during walking (P < 0.05), but not during running and the efficiency of locomotion was similar in all subjects and speeds. The higher cost of walking in Pygmies is consistent with the allometric prediction for smaller subjects. The major determinants of the higher cost of walking was the difference in stride frequency (+9.45, SD 0.44% for Pygmies), which affected the mechanical internal work. This explains the observed higher total mechanical work of walking in Pygmies, even when the external component was the same. Most of the differences between Pygmies and Caucasians, observed during walking, tended to disappear when the speed was normalized as the Froude number. However, this was not the case for running. Thus, whereas the tested hypothesis must be rejected for walking, the data from running, do indeed suggest that Pygmies may differ in some aspects of the mechanics of locomotion.

Adult↗
PubMed1994

Modified fluidity and lipid composition in lipoproteins and platelet membranes from diabetic patients.

The interaction between lipoproteins and the platelet membrane has been proved to cause a modification in cellular functions. We studied 12 men with insulin-dependent diabetes mellitus (IDDM), 14 men with noninsulin-dependent diabetes mellitus (NIDDM), and 26 age-matched healthy men on the same diet. We determined fluidity by measuring the fluorescence polarization (P) of the probe 1,6-diphenyl-1,3,5-hexatriene (DPH) both in platelet membranes and in lipoproteins isolated by ultracentrifugation in NaBr density gradient. The lipid composition of lipoproteins and of platelet membranes was determined by enzymatic methods. The fluidity of platelet membranes was significantly increased both in patients affected by NIDDM and in subjects with IDDM compared with normal subjects. Low-density lipoproteins (LDL) showed an increased fluidity only in NIDDM patients. A percent increase in the triglyceride content was observed in all lipoprotein fractions in diabetic subjects. Increased phospholipid content was found in the platelet membranes from IDDM and NIDDM patients. The change in LDL fluidity observed in NIDDM patients might determine altered interactions between the lipoprotein and cellular receptors. The role of lipoproteins in the modulation of the platelet membrane properties in diabetes mellitus deserves further studies.

Adult↗