Boris Holm

Effects of physical and apnea training on apneic time and the diving response in humans

Abstract The aim of this investigation was to study separately the effects of physical training and apnea training on the diving response and apneic time in humans. Both types of training have been suggested to lead to prolonged apneic time and an increased “diving response” (i.e., regional vasoconstriction and bradycardia). The study was also designed to examine the effects of these two types of training on the characteristics of the increase in apneic time with repeated apneas. Simulated diving tests were performed before and after the different training programs. The test format was one apnea and five apneas with facial immersion in cold water at 2-min intervals. An increase in apneic time was observed after physical training (n=24), and this was attributable to an increased time beyond the physiological breaking point. The other parameters that were measured remained unaffected. After apnea training (n=9), however, apneic time was increased by a delay in the physiological breaking point, which is mainly determined by the arterial tension of CO2. The diving response had increased, and the effect of repeated apneas on apneic time tended to be larger after apnea training. These results may explain the pronounced diving responses and long apneas observed in trained apneic divers.

Cardiovascular responses to cold water immersions of forearm and face and their relationship to apnoea

Abstract Apnoea as well as cold stimulation of the face or the extremities elicits marked cardiovascular reflexes in humans. The purpose of this study was to investigate whether forearm immersion in cold water has any effect on the cardiovascular responses to face immersion and apnoea. We recorded cardiovascular responses to cold-water immersions of the forearm and face in 19 (part I) and 23 subjects (part II). The experimental protocol was divided in two parts, each part containing four tests: I1, forearm immersion during eupnoea; I2, face immersion during eupnoea; I3, forearm and face immersion during eupnoea; I4, face immersion during apnoea; II1, apnoea without immersion; II2, forearm immersion during apnoea; II3, face immersion during apnoea; and II4, forearm and face immersion during apnoea. The water temperature was 9–11 °C. Cold-water immersion of either the forearm or face was enough to elicit the most pronounced thermoregulatory vasoconstriction during both eupnoea and apnoea. During eupnoea, heart rate responses to forearm immersion (3% increase) and face immersion (9% decrease) were additive during concurrent stimulation (3% decrease). During apnoea, the heart rate responses were not affected by the forearm immersion. The oxygen-conserving diving response seems to dominate over thermoregulatory responses in the threat of asphyxia. During breathing, however, the diving response serves no purpose and does not set thermoregulatory adjustments aside.

Effects of water and ambient air temperatures on human diving bradycardia

Upon apnoeic face immersion, humans develop a diving response resembling that found in diving mammals. There have been contradictory reports regarding the influence of water temperature on the magnitude of the resulting bradycardia. This study examined the influence of both water and ambient air temperatures on human diving bradycardia. A group of 23 volunteers performed three series of apnoeic episodes after 60-min exposure to air at temperatures of 10, 20 or 30°C. Oral and skin temperatures were measured during this exposure and during the subsequent test on 5 subjects. At 20°C air temperature oral and skin temperatures were measured on 10 subjects. Heart rate (HR) was recorded for the 23 subjects during apnoea in air and apnoea with the face immersed in water of 10, 20 or 30°C, at each air temperature. We found that both air and water temperatures had significant effects on immersion bradycardia, but in opposite directions. Face immersion in cold water after exposure to a high ambient air temperature induced the most pronounced bradycardia. We further observed that exposure to different ambient air temperatures resulted in different patterns of HR response to water temperature. The range in which the response was positively correlated to water temperature differed at 30°C ambient air from that at 10 and 20°C ambient air. We concluded from these studies that human bradycardia resulting from apnoeic face immersion is inversely proportional to water temperature within a range which is determined by the ambient air temperature. Thus, the interval in which the response to cold stimulation varies with temperature, would appear to be determined by the ambient temperature before stimulation.

Inverted reactivity of aryllithium derivatives V. On the syntheses of thiocyano-, phenylsulfinyl-, and phenoxy derivatives of thiophenes and furans

The reaction of some diheterocyclic iodonium salts with a variety of nucleophiles has been studied. The reaction was of preparative use for the syntheses of thiocyano, phenylsulfinyl and phenoxy derivatives of thiophenes and furans.

Inverted Reactivity of Aryllithium Derivatives III. Convenient Syntheses of Isomer-Free 3-Nitrofuran and 2- and 3-Nitroselenophene

Abstract A recent paper by Paulmier et al.1 on the synthesis of selenolo-[2,3-b]- and selenolo[3,2-b]pyridine, for which 2- and 3-nitroselenophene were used as starting materials, prompts us to publish convenient procedures for the syntheses of these compounds and also for 3-nitrofuran. We needed these compounds in connection with our 13C NMR studies of heterocyclic systems.

Uptake of Putrescine by Tetrahymena

SummaryThe uptake of the diamine 3H-putrescine by Tetrahymena pyriformis GL was studied in cultures which were synchronized by heat shocks. An inverse correlation was found between the uptake of putrescine and the acid stability of DNA, but there was also a parallelism between putrescine uptake and the intracellular amount of putrescine. There was no evidence for a transformation of the labeled putrescine to other amino compounds within the cells. Electronmicroscopical autoradiography showed a structure-bound radioactivity localized to nuclear and mitochondrial structures. In the nucleus, both the chromatin and the nucleoli showed labeling.