The aim of the present work was to study the cadmium effects on growth, ultrastructure and polyphosphate metabolism, as well as to evaluate the metal removal and accumulation by Cunninghamella elegans (IFM 46109) growing in culture medium. The presence of cadmium reduced growth, and a longer lag phase was observed. However, the phosphate uptake from the culture medium increased 15% when compared to the control. Moreover, C. elegans removed 70%–81% of the cadmium added to the culture medium during its growth. The C. elegans mycelia showed a removal efficiency of 280 mg/g at a cadmium concentration of 22.10 mg/L, and the removal velocity of cadmium was 0.107 mg/h. Additionally, it was observed that cadmium induced vacuolization, the presence of electron dense deposits in vacuoles, cytoplasm and cell membranes, as well as the distinct behavior of polyphosphate fractions. The results obtained with C. elegans suggest that precipitation, vacuolization and polyphosphate fractions were associated to cadmium tolerance, and this species demonstrated a higher potential for bioremediation of heavy metals.

Exercise involves the interaction of several physiological processes, in which adjustments in pulmonary ventilation occur in response to increased O 2 consumption, CO 2 production and altered acid-base equilibrium. The peripheral chemoreceptors (carotid bodies; CBs) are sensitive to changes in the chemical composition of arterial blood, and their activation induces active inspiratory and expiratory responses. Herein, we tested the hypothesis that the CBs contribute to the active inspiratory and expiratory responses to exercise in rats. We performed electromyographic recordings of the diaphragm (Dia EMG) and abdominal internal oblique (Abd EMG) muscles in rats before and after bilateral removal of the CBs (CBX) during constant-load low-intensity and high-intensity progressive treadmill exercise. We also collected arterial blood samples for gaseous and pH analyses. Similar increases in Dia EMG frequency in both experimental conditions (before and after CBX) during low-intensity exercise were observed, without significant changes in the Dia EMG amplitude. During high-intensity exercise, lower responses of both Dia EMG frequency and Dia EMG amplitude were observed in rats after CBX. The Abd EMG phasic active expiratory response was not significant either before or after CBX during low-intensity exercise. However, CBX reduced the phasic active expiratory responses during high-intensity exercise. The blunted responses of inspiratory and expiratory adjustments to high-intensity exercise after CBX were associated with higher P aCO 2 levels and lower arterial pH values. Our data show that in rats the CBs do not participate in the inspiratory and expiratory responses to low-intensity exercise, but are involved in the respiratory compensation against the metabolic acidosis induced by high-intensity exercise.

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