This study investigated whether changing sympathetic activity, acting via beta-receptors, might induce the progressive ventilatory changes observed in response to prolonged hypoxia. The responses of 10 human subjects to four 8-h protocols were compared: 1) isocapnic hypoxia (end-tidal PO2 = 50 Torr) plus 80-mg doses of oral propranolol; 2) isocapnic hypoxia, as in protocol 1, with oral placebo;...

Hypoxia may sensitize the carotid chemoreceptors, resulting in a sustained elevation of muscle sympathetic nerve activity (MSNA) that outlasts the hypoxic stimulus. To test this hypothesis, we determined the effect of carotid body inhibition on the sustained elevation of MSNA following isocapnic hypoxia in humans. Seven healthy subjects (5 male, 2 female) breathed 100% O(2) (hyperoxia) for 1 mi...

We sought to characterize and quantify the performance of a portable dynamic end-tidal forcing (DEF) system in controlling the partial pressure of arterial CO2 (Pa(CO2)) and O2 (Pa(O2)) at low (LA; 344 m) and high altitude (HA; 5,050 m) during an isooxic CO2 test and an isocapnic O2 test, which is commonly used to measure ventilatory and vascular reactivity in humans (n = 9). The isooxic CO2 te...

Bronchoconstriction was induced in asthmatic patients by means of isocapnic hyperventilation with dry air. Responses both within a day and between days did not differ significantly and corresponded closely with those observed after exercise. The mean fall in forced expiratory volume in one second (FEV1) observed with both techniques was equivalent to 36%. Isocapnic hyperventilation with dry air...

The effects of progressive isocapnic hypoxia on the systolic time intervals were studied in 10 healthy human subjects. We induced hypoxia by a rebreathing method and monitored the arterial oxygen saturation continuously and non-invasively by means of an ear oximeter. Arterial oxygen saturation (SaO2) was allowed to fall to a level of 75 per cent and was then held constant for five minutes. As S...

The buffering capacity inside thylakoids is determined and the magnitude of flash-induced pH changes inside is calibrated in the pH range from 6.4 to 8.1. The work is based on flash-induced absorption changes of neutral red in a chloroplast suspension in which the outer phase is strongly buffered by bovine serum albumin. It is shown that neutral red is bound inside thylakoids. The binding can b...

In this paper we propose a multi-set modulation technique to increase the hiding capacity within a binary document image. As part of this technique we propose an Automatic Threshold Calculation and Threshold Buffering, Shifted Space Distribution and Letter Space Compensation technique. The Automatic Threshold Calculation is used to distinguish word spaces from letter spaces. The Threshold Buffe...

In randomly connected networks of pulse-coupled elements a time-dependent input signal can be buffered over a short time. We studied the signal buffering properties in simulated networks as a function of the networks' state, characterized by both the Lyapunov exponent of the microscopic dynamics and the macroscopic activity derived from mean-field theory. If all network elements receive the sam...