B. Grassi, G. Ferretti, B. Kayser, M. Marzorati, A. Colombini, C. Marconi and P. Cerretelli
Section of Physiology, Istituto di Technologie Biomediche Avanzate, Consiglio Nazionale delle Ricerche, ...Milan, Italy.
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.
This collection of original articles and surveys treats linear and nonlinear aspects of the theory of partial differential equations. Phase space analysis methods, also known as microlocal analysis, ...have yielded striking results over the past years and have become one of the main tools of investigation. Equally important is their role in many applications to physics, for example, in quantum and spectral theory. Contributors: H. Bahouri, M. Baouendi, E. Bernardi, M. Bony, A. Bove, N. Burq, J.-Y. Chemin, F. Colombini, T. Colin, P. Cordaro, G. Eskin, X. Fu, N. Hanges, G. Métivier, P. Michor, T. Nishitani, A. Parmeggiani,L. Pernazza, V. Petkov, F. Planchon, M. Prizzi, D. Del Santo, D. Tartakof, D. Tataru, F. Treves, C.-J. Xu, X. Zhang, E. Zuazua
Oxygen consumption (VO2) in ml.kg-1.min-1, blood lactate concentration (La in mM) and dynamic friction of the skis on snow (F) in N were measured in six athletes skiing on a level track at different ...speeds (v) in m.min-1 and using different methods of propulsion. The VO2 increased with v and F, the latter depending mostly on snow temperature, as did La. The VO2 was very much affected by the skiing technique. Multiple regression equations gave the following results: with diagonal stride (DS), VO2 = -23.09 + 0.189 v + 0.62 N; with double pole (DP), VO2 = -30.95 + 0.192 v + 0.51 N; and with the new skating technique (S), VO2 = -32.63 + 0.171 + 0.68 N. In terms of VO2 DS is the most expensive technique, while S is the least expensive; however, as F increases, S, at the highest speed, tends to cost as much as DP. At speeds from 18 to 22 km.h-1, the speeds measured in the competitions, the F for DS and DP can represent from 10% to 50% of the energy expenditure, with F ranging from 10 to 60 N; with S this range increases to 20%-70%. This seems to depend on the interface between the skis and the snow and on the different ways the poles are used.
The average maximal peak torques of the knee extensor and knee flexor muscles were measured during one, two or three series of 20 maximal contractions at an angular velocity of pi rad s -1 . After ...the first series, a 10 min rest was allowed before the second series of contractions. In one case only was a third series of contractions performed. Various sequences of contractions of the dominant and contralateral limbs were tested. Capillary blood lactate concentration (LA cap ) was determined in the blood samples taken from an earlobe during each recovery. The difference between peak capillary blood lactate concentration and the concentration that would have occurred without any previous contraction (deltaLA cap ) was taken as the index of metabolic comparison between the exercise bouts. The mechanical power output during the first series of contractions was similar to that in the second and third series, but the lactate elevation was significantly higher in the first series. The discrepancy between the constancy of the power output and the decrease in lactate elevation was even more evident if deltaLA cap was calculated as the difference between peak capillary blood lactate concentration and the value measured immediately before the second or third series. The decrease in lactate elevation was not affected by the change of the contracting limb from the first to the second series. In conclusion, the capillary blood lactate concentration profile during intermittent maximal exercise cannot be considered a suitable technique for evaluating lactate production. Each series lasted about 20 s.
Motor fluctuations not controlled by pharmacological therapy are often encountered in long-term Parkinson's disease (PD). Neurosurgery treatment represented by deep brain stimulation (DBS) was ...considered a valid alternative to pharmacological treatment. Unfortunately this method is most effective in patients under age of 70. Recently it has been suggested that extradural motor cortex stimulation (EMCS) could be a valid cost-effective alternative to DBS to control motor symptoms in patients affected by Parkinson's disease. The relevant non-invasive surgical technique makes this treatment particularly indicated in geriatric patients. Brain atrophy, cognitive impairment, psychiatric symptoms are not an absolute contraindication to the treatment. We submitted to EMCS an outpatient afferent to our geriatric department, a woman 68 yrs old. The patient showed an improvement of 35% as measured by the Unified Parkinson Disease Rating Scale (UPDRS) scale after the surgery. If our findings will be confirmed in larger series, a new dimension will be added to the treatment of PD.
Twenty-four Mediterranean fin whales were tracked in open sea with a method based on the assessment of the animal differential position in respect of the observer's absolute position aboard a vessel, ...with the concomitant recording of the respiratory activity. Short distance video recording was also performed in two whales, permitting the simultaneous determination of single breath expiratory (TE) and inspiratory (TI) durations. In the 24 whales swimming at an average velocity of 1.39 (0.47) m.s(-1) mean (SD), range: 0.62-2.44 m.s(-1), 2068 breaths organized in 477 respiratory cycles were observed. Each cycle entailed a prolonged apnoea dive phase 225 (91) s, Tdive) followed by a period near the surface 62 (28) s, surfacing, during which a series of breaths 4.6 (1.8) was performed at short intervals. On the basis of track length and swimming velocity, two groups of animals were devised differing for convolution of the course (p<0.001), extension of ranging territory (p<0.01) and horizontal swimming velocity (p<0.05), which may represent two distinct behaviours. A possibly general mechanism of control of breathing in cetaceans was found, consistent with a model of constant tidal volume and variable respiratory frequency. Coherently with this model, TE was independent of TI or Tdive, in line with a passive expiration, while TI appeared to be negatively correlated with Tdive (p<0.05), otherwise suggesting, similarly with terrestrial mammals, a significant role of hypercapnic stimulation. The estimated O2 consumption of about 150 l.min(-1) is in line with the general allometric regression for mammals and corresponds to an energetic expenditure of 85-95 kJ.kg(-1).day(-1).
A 4-year-old boy with acute myeloid leukemia developed acute myositis associated with refractory thrombocytopenia one month after autologous bone marrow transplantation (BMT). Clinical, ...electromyographic and biohumoral features were consistent with the diagnosis of myositis. The patient responded to corticosteroids, and 39 months after BMT he is in complete remission and has regained good muscle function. Although we could not determine with certainty the specific pathophysiologic mechanism of this complication, it should be pointed out that acute myositis can occur in the early post-BMT period.
