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Biomedical subjects

G Antonutto

Publications and source records attributed to G Antonutto.

At least 37 records · Page 2Linked to original sources
PubMed1995

The concept of lactate threshold. A short review.

The anaerobic threshold (AT) is a widely used tool for investigating aerobic performance characteristics in physiological of pathological conditions. The aim of the present paper is to show that, when the lactate concentration in blood [Lab] is constant in time, regardless of its absolute level, the whole body energy sources for muscular work are entirely aerobic. In fact, [Lab] can remain constant if, and only if, La production is equal to La removal. Since this last is an entirely aerobic process, it can be shown that the net anaerobic energy yield from La production is nil, even if some muscle fibres are indeed producing La at a non trivial rate. These conditions will be defined as "unevenly aerobic" to distinguish them from: (1) the traditional "evenly aerobic" ones, in which the net La production is also zero, but because neither La production nor La removal are significantly increased, and (2) "true anaerobic" conditions wherein La production exceeds La removal and therefore [Lab] increases continuously in time. Comparison of unevenly versus evenly aerobic conditions shows that in the former case the depletion of the glycogen stores is faster in the muscles (or muscle fibres) that are producing La than in those which remove it. Hence the La producing fibres may become crucial in setting the duration (or intensity) of performance. AT, irrespective of its precise mode of assessment, is presumably a measure of the exercise intensity corresponding (or close) to the transition between evenly and unevenly aerobic conditions, thus explaining why AT is a good estimate of the subjects' training status and/or performance capacity.

Aerobiosis↗
PubMed1994

Assessment of cardiac output from noninvasive determination of arterial pressure profile in subjects at rest.

The stroke volume of the left ventricle (SV) was calculated from noninvasive recordings of the arterial pressure using a finger photoplethysmograph and compared to the values obtained by pulsed Doppler echocardiography (PDE). A group of 19 healthy men and 12 women [mean ages: 20.8 (SD 1.6) and 22.2 (SD 1.6) years respectively] were studied at rest in the supine position. The ratio of the area below the ejection phase of the arterial pressure wave (A(s)) to SV, as obtained by PDE, yielded a "calibration factor" dimensionally equal to the hydraulic impedance of the system (Zao = A(s).SV-1). The Zao amounted on average to 0.062 (SD 0.018) mmHg.s.cm-3 for the men and to 0.104 (SD 0.024) mmHg.s.cm-3 for the women. The Zao was also estimated from the equation: Zao = a.(d + b.HR + c.PP + e.MAP)-1, where HR was the heart rate, PP the pulse pressure, MAP the mean arterial pressure and the coefficients of the equation were obtained by an iterating statistical package. The value of Zao thus obtained allowed the calculation of SV from measurements derived from the photoplethysmograph only. The mean percentage error between the SV thus obtained and those experimentally determined by PDE amounted to 14.8 and 15.6 for the men and the women, respectively. The error of the estimate was reduced to 12.3 and to 11.1, respectively, if the factor Zao, experimentally obtained from a given heart beat, was subsequently applied to other beats to obtain SV from the A(s) measurement in the same subject.

Adult↗
PubMed1993

Effects of prolonged cycle ergometer exercise on maximal muscle power and oxygen uptake in humans.

The mechanical power (Wtot, W.kg-1) developed during ten revolutions of all-out periods of cycle ergometer exercise (4-9 s) was measured every 5-6 min in six subjects from rest or from a baseline of constant aerobic exercise [50%-80% of maximal oxygen uptake (VO2max)] of 20-40 min duration. The oxygen uptake [VO2 (W.kg-1, 1 ml O2 = 20.9 J)] and venous blood lactate concentration ([la]b, mM) were also measured every 15 s and 2 min, respectively. During the first all-out period, Wtot decreased linearly with the intensity of the priming exercise (Wtot = 11.9-0.25.VO2). After the first all-out period (t greater than 5-6 min), and if the exercise intensity was less than 60% VO2max, Wtot, VO2 and [la]b remained constant until the end of the exercise. For exercise intensities greater than 60% VO2max, VO2 and [la]b showed continuous upward drifts and Wtot continued decreasing. Under these conditions, the rate of decrease of Wtot was linearly related to the rate of increase of VO2 [(dWtot/dt) (W.kg-1 x s-1) = 5.0 x 10(-5) -0.20.(VO2/dt) (W.kg-1 x s-1)] and this was linearly related to the rate of increase of [la]b [(dVO2/dt) (W.kg-1 x s-1) = 2.3 x 10(-4) + 5.9 x 10(-5).(d[la]b/dt) (mM.s-1)].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Energetics of best performances in middle-distance running.

Oxygen consumption (VO2) and blood lactate concentration were determined during constant-speed track running on 16 runners of intermediate level competing in middle distances (0.8-5.0 km). The energy cost of track running per unit distance (Cr) was then obtained from the ratio of steady-state VO2, corrected for lactate production, to speed; it was found to be independent of speed, its overall mean being 3.72 +/- 0.24 J.kg-1 x m-1 (n = 58; 1 ml O2 = 20.9 J). Maximal VO2 (VO2max) was also measured on the same subjects. Theoretical record times were then calculated for each distance and subject and compared with actual seasonal best performances as follows. The maximal metabolic power (Er max) a subject can maintain in running is a known function of VO2max and maximal anaerobic capacity and of the effort duration to exhaustion (te). Er max was then calculated as a function of te from VO2max, assuming a standard value for maximal anaerobic capacity. The metabolic power requirement (Er) necessary to cover a given distance (d) was calculated as a function of performance time (t) from the product Crdt-1 = Er. The time values that solve the equality Er max(te) = Er(t), assumed to yield the theoretical best t, were obtained by an iterative procedure for any given subject and distance and compared with actual records.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Blood lactate during leg exercise in microgravity.

Venous blood lactate concentration ([La]b) was measured in five male subjects (age: 30-50 years; BW: 72-84 kg, VO2max:2.2-3.6 l min-1) during cycloergometric exercise in microgravity obtained by parabolic flight maneuvers of approximately 25 s duration. The subject(s) exercised at 30, 60, 90 and 120 W (60 RPM) for at least 7 min at each intensity. Three consecutive parabolas with approximately 3 min interval were performed at each workload. [La]b was determined at rest and immediately after 60, 90 and 120 W exercise. The day after the flight experiments, the subject(s) underwent the same experimental protocol on the ground and the blood samples were taken at the very same time intervals as on the aircraft. [La]b in flight and control didn't show any appreciable difference once the values are plotted as a function of the relative exercise intensities expressed as a percent of the individual VO2max corrected for the moderate hypoxia prevailing inside the aircraft (cabin barometric pressure = 590 mmHg).

Adult↗
PubMed1992

Artificial gravity in Space: vestibular tolerance assessed by human centrifuge spinning on Earth.

Artificial gravity created by the astronauts themselves, without any external power supply, by pedalling on coupled counterrotating bicycles along the inner wall of the space module (Twin Bikes System, TBS), was previously suggested (Antonutto et al., 1991) to prevent musculo-skeletal decay and cardiovascular deconditioning during long term space flights. To investigate whether this unusual rotating environment would determine abnormal stimulations of the vestibular system due to Coriolis cross coupled accelerations, thus leading to acute motion sickness (AMS), the conditions of a rotating environment were reproduced in a human centrifuge. A cycloergometer was fixed to the arm of the centrifuge, the rotation speed of which was equal to that yielding 1 g at the feet level in the TBS (i.e. ranging from 19 to 21 RPM). The ergometer position was such that the combination of the horizontal and gravitational acceleration vectors was 1.414 at the inner ear level and was aligned along the head to feet axis. Three subjects, pedalling at 50 W on a cycloergometer during centrifuge's spinning, were asked to move the head following an AMS' provocation protocol. None of them developed any AMS symptoms. This supports the look of the TBS as tool for avoiding musculo-skeletal and cardiovascular deconditioning during long term space flights.

Adult↗
PubMed1991

Pedalling in space as a countermeasure to microgravity deconditioning.

A system consisting of two mechanically coupled counter rotating bicycles, moving on the inner wall of a cylindrical space module, is proposed to prevent microgravity deconditioning. The two pedalling subjects generate a centrifugal acceleration vector (ac) simulating gravity. This last depends on the peripheral velocity (v) and on the radius of gyration (R): ac = v2/R. Since R is constant and equal to the inner radius of the space module, any desired value of ac can be achieved by selecting the appropriate v value. The corresponding mechanical (w) and metabolic (VO2) powers can then be calculated on the basis of the biomechanical and anthropometric characteristics of the system and subjects. It is shown that if R = 2 m, in order to attain ac = 1 g at the feet, v = 4.5 m s-1, w = 60 W and VO2 = 1.2 litres min-1. However if R = 6 m, then v = 7.8 m s-1, w = 140 W and VO2 = 3 litres min-1. The average arterial pressures prevailing at the head and feet levels in the two above conditions can also be calculated as 95, 150 and 80, 170 mmHg, respectively for a mean arterial pressure of 100 mmHg at the aortic bulbus. In conclusion, by selecting appropriately the radial dimensions of the space module in order to minimize: (1) vestibular disturbances, (2) head to feet centrifugal acceleration gradients and (3) manufacturing costs, it may be possible to combine exercise and simulated gravity, with no need for additional external power.

Aerospace Medicine↗
PubMed1983

Amyloidosis of specialized mesodermal tissues in non-myelomatous monoclonal gammopathy. A pathogenetic hypothesis.

The follow-up and the pathological findings of a previously described case of non-myelomatous monoclonal gammopathy with relapsing localized amyloid masses of the shoulder joints are reported. The peculiar "mesodermal" distribution of amyloid deposits, strictly limited to tissues lined by mesothelial or endothelial cells emphasizes the role of local factors in the pathogenesis of amyloidosis thus supporting the hypothesis that amyloid deposition can be related also to some differentiated tissues with peculiar local susceptibility. The morphological findings of the present case enable the Authors to suggest a pathogenic mechanism for amyloid deposition.

Aged↗
PubMed1983

Alpha-heavy chain disease. Report of a case with spontaneous regression.

The occurrence of alpha-heavy chain disease in an Italian adult, working in Libya, is reported, characterized by a spontaneous clinical and immunological recovery. It is suggested that the patient could have acquired the disease during his stay in an endemic area of alpha-heavy chain disease, and that the observed spontaneous remission could be related to the removal of environmental pathogenic factors, following his departure from Libya.

Adult↗
PubMed1980

Pseudotumoral (para-articular) amyloidosis in non-myelomatous monoclonal gammopathy.

A case of non-myelomatous monoclonal gammopathy, with the unusual presenting features of recurrent "pseudotumoral" localized amyloid deposits in intimate relation with the shoulder joints, is described. The peculiar anatomo-clinical features, which make this case quite different from the most reported ones of amyloid arthropathy and of localized amyloidosis, are discussed. The pathogenetic implications are analyzed with special reference to the various known mechanisms, none of which seems to provide a completely satisfactory explanation of the genesis of this form.

Aged↗
PubMed1980

Pathology of ocular tissues in amyloidosis.

Ocular involvement was found in 29 autopsied individuals with generalized vascular amyloidosis. It may be present both in clinically primary and secondary amyloidosis. In the latter form the choroid and the sclera are particulary involved, whereas in the orbit the most frequently affected tissues in both forms are the extraocular muscles. However, in most cases amyloid deposits are localized in the vessels of the aterial circle of Zinn-Haller. The retina showed no involvement in 28 of 29 cases while optic nerve fibres never were affected. The optic nerve dural sheath was slightly involved in 8 cases.

Aged↗
PubMed1979

Amyloidosis of the pancreas: histochemical differentiation between insular and extrainsular deposits.

The results of a study of eighty-two human pancreases affected by deposits of amyloid in the islets of Langerhans are presented. Two different types of amyloid deposits were observed, one affecting the exocrine tissue and the other affecting the islets. These deposits were found to be histochemically different and appeared to indicate two different aetiopathogenetic processes. The deposit found in the exocrine tissue is essentially perivascular and might be considered an extension to the pancreas of a systemic amyloidosis of the "senile type"; the islet deposits appear to be a completely different phenomenon that could become part of the biology and pathology peculiar to the so called APUD system. The coexistence of the two types of amyloid in the human pancreas would seem, therefore, to represent a casual event.

Aged↗