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PubMed1998

VO2/power output relationship and the slow component of oxygen uptake kinetics during cycling at different pedaling rates: relationship to venous lactate accumulation and blood acid-base balance.

In this experiment we studied the effect of different pedalling rates during cycling at a constant power output (PO) 132+/-31 W (mean+/-S.D.), corresponding to 50% VO2 max, on the oxygen uptake and the magnitude of the slow component of VO2 kinetics in humans. The PO corresponded to 50% of VO2 max, established during incremental cycling at a pedalling rate of 70 rev.min(-1). Six healthy men aged 22.2+/-2.0 years with VO2 max 3.89+/-0.92 l.min(-1), performed on separate days constant PO cycling exercise lasting 6 min at pedalling rates 40, 60, 80, 100 and 120 rev.min(-1), in random order. Antecubital blood samples for plasma lactate [La]pl and blood acid-base balance variables were taken at 1 min intervals. Oxygen uptake was determined breath-by-breath. The total net oxygen consumed throughout the 6 min cycling period at pedalling rates of 40, 60, 80, 100 and 120 rev.min(-1) amounted to 7.727+/-1.197, 7.705+/-1.548, 8.679+/-1.262, 9.945+/-1.435 and 13.720+/-1.862 l, respectively for each pedalling rate. The VO2 during the 6 min of cycling only rose slowly by increasing the pedalling rate in the range of 40-100 rev.min(-1). This increase, was 0.142 l per 20 rev.min(-1) on the average. Plasma lactate concentration during the sixth minute of cycling changed little within this range of pedalling rates: the values were 1.83+/-0.70, 1.80+/-0.48, 2.33+/-0.88 and 2.52+/-0.33 mmol.l(-1). The values of [La]pl reached in the 6th minute of cycling were not significantly different from the pre-exercise levels. Blood pH was also not affected by the increase of pedalling rate in the range of 40-100 rev.min(-1). However, an increase of pedalling rate from 100 to 120 rev.min(-1) caused a sudden increase in the VO2 amounting to 0.747 l per 20 rev.min(-1), accompanied by a significant increase in [La]pl from 1.21+/-0.26 mmol.l(-1) in pre-exercise conditions to 5.92+/-2.46 mmol.l(-1) reached in the 6th minute of cycling (P<0.01). This was also accompanied by a significant drop of blood pH, from 7.355+/-0.039 in the pre-exercise period to 7.296+/-0.060 in the 6th minute of cycling (P < 0.01). The mechanical efficiency calculated on the basis of the net VO2 reached between the 4th and the 6th minute of cycling amounted to 26.6+/-2.7, 26.4+/-2.0, 23.4+/-3.4, 20.3+/-2.6 and 14.7+/-2.2%, respectively for pedalling rates of 40, 60, 80, 100 and 120 rev.min(-1). No significant increase in the VO2 from the 3rd to the 6th min (representing the magnitude of the slow component of VO2 kinetics) was observed at any of the pedalling rates (-0.022+/-0.056, -0.009+/-0.029, 0.012+/-0.073, 0.030+/-0.081 and 0.122+/-0.176 l.min(-1) for pedalling rates of 40, 60, 80, 100 and 120 rev.min(-1), respectively). Thus a significant increase in [La]pl and a decrease in blood pH do not play a major role in the mechanism(s) responsible for the slow component of VO2 kinetics in humans.

Acid-Base Equilibrium↗
PubMed1975

Relationships between specialized cells, capillaries, and intermediary cyto-fibrillar elements. Vth note. Organizational steps or levels of these relationships during their biological development.

The developmental analysis of the interrelations between specialized cells, capillaries, and intermediary cyto-fibrillar elements points out the existence of four organizational steps reflecting the gradual increase in complexity and diversity of animal structures and functions. The development of secretory and defence functions produces a dissociation of steps between the increase of the organizational level of the whole animal organism and the autonomy of organizational steps or organs. The steps are not immovable, but under some conditions the possibility of a mutation exists between the IInd and the IIIrd steps.

Animals↗
PubMedDate not supplied

Relationships between specialized cells, capillaries, and intermediary cytofibrillary elements. VIIth note. Epitheliocapillary relationships in hypothysis and thyroid during experimentally conditioned immunity.

The participation of the thyroid and of the anterior hypophysis during a complex process of experimentally conditioned immunity was studied in order to establish the concrete modalities of integration of these glands by the central integrative mechanisms. Quantitative microscopy, mathematical and statistical methods, demonstrative graphs, a new mode of expression of correlation types between the phasic quantitative variations of the immune process, as well as a division of the anterior hypophysis into cell groups were used. These methods show that the hypophysis and the thyroid participate in the immunogenic processes with all their constituents (epithelia, mesenchymal cells, capillaries). The importance of the participation vary from one lot to the other. The epithelium dynamics dominated that of capillaries in the glandular organs belonging to the IInd organizational step (with reduced stroma), which allows the consideration of an epitheliocapillary stereotype of organs belonging to the IIIrd step (stroma-rich) described in the VIth note.

Animals↗