The respiratory effects of forced changes of alveolar PCO2 were studied in four healthy human subjects and in one anaesthetized cat. Solenoid valves, triggered by changes in mouth pressure, allowed changes from one inspiratory gas mixture to another, either during expiration (between-breath changes, BBC) or in the middle of inspiration (within-breath changes, WBC). In BBC the subject breathed CO2-free gas in one inspiration, CO2-rich gas in the next, and so on; end-tidal PCO2 alternated regularly from breath to breath by 1.1 kPa. In WBC CO2-free gas was given early in one inspiration and late in the next, with CO2-rich gas late in the former and early in the latter, and so on end-tidal PCO2 was nearly constant from breath to breath. Eight respiratory output variables were analysed. WBC induced small but significant alternation in most of the variables; these effects occurred almost exclusively in runs in hypoxia. The responses were not very different from those seen in BBC. The experiment on the cat showed that the alveolar PCO2 changes predicted during WBC are reflected by changes in pH in the arterial blood. The results confirm predictions based upon observations in the steady state of tube- and reversed-tube breathing in man. It seems likely that the responses are mediated by the arterial chemoreceptors responding to small changes in the profile of the (CO2, H+) oscillation.

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The present study was designed to examine the effect of heme oxygenase-1 (HO-1) induction by cobalt protoporphyrin (CoPP) on the cardiac functions and morphology, electrocardiogram (ECG) changes, myocardial antioxidants (superoxide dismutase [SOD] and glutathione [GSH]), and expression of heat shock protein (Hsp) 70 and connexin 43 (Cx-43) in myocardial muscles in isoproterenol (ISO) induced myocardial infarction (MI). Thirty two adult male Sprague Dawely rats were divided into 4 groups (each 8 rats): normal control (NC) group, ISO group: received ISO at dose of 150 mg/kg body weight intraperitoneally (i.p.) for 2 successive days; ISO + Trizma group: received (ISO) and Trizma (solvent of CoPP) at dose of 5 mg/kg i.p. injection 2 days before injection of ISO, with ISO at day 0 and at day 2 after ISO injections; and ISO + CoPP group: received ISO and CoPP at a dose of 5 mg/kg dissolved in Trizma i.p. injection as Trizma. We found that, administration of ISO caused significant increase in heart rate, corrected QT interval, ST segment, cardiac enzymes (lactate dehydrogenase, creatine kinase-muscle/brain), cardiac HO-1, Hsp70 with significant attenuation in myocardial GSH, SOD, and Cx-43. On the other hand, administration of CoPP caused significant improvement in ECG parameters, cardiac enzymes, cardiac morphology; antioxidants induced by ISO with significant increase in HO-1, Cx-43, and Hsp70 expression in myocardium. In conclusions, we concluded that induction of HO-1 by CoPP ameliorates ISO-induced myocardial injury, which might be due to up-regulation of Hsp70 and gap junction protein (Cx-43).

FR and Ex seems to improve the motor performance in PD rodent model which might be due to upregulation of Hsp70 and increasing density of dopaminergic neurons in corpus striatum. FR offers more protective effects than Ex and combination of both did not offer more protection than FR alone.

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