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PubMedDate not supplied

[The readaptation of the respiration, blood circulation and body oxygen regimen in aquanauts after saturation dives to depths of up to 450 m].

Main trace posthyperbaric and postdecompression responses to respiration, circulation and oxygen profiles, dynamics of their reduction in 99 aquanauts at pressure of 46 kgs/cm2 (0.46 mPa) during 14-30 day period have been studied. The respiratory changes were found to be characterized by: ventilatory function disorders which followed the obstructive-restrictive pattern; discoordination of ventilation regulation and slowing down of respiratory gas transport through aerohematic barrier. The hemodynamic shifts have been manifested as cardiac rhythm instability, heart pump function followed by decreased cardiac contractions on exercise exposures. The economy and efficiency of body oxygen profiles in a respiration loop become lower than that in hemodynamic loop. The rate of the alveolar oxygen supply is decreased to the levels lower than the rates of oxygen supply by arterial and mixed venous blood. The long-term functional rearrangement of respiratory gas transport followed by the phase changes combined with the specific and nonspecific reactions persisting over a period of 30-60 days and more longer after decompression, is existed.

Adaptation, Physiological↗
PubMed2006

The effects of acute oral antioxidants on diving-induced alterations in human cardiovascular function.

Diving-induced acute alterations in cardiovascular function such as arterial endothelial dysfunction, increased pulmonary artery pressure (PAP) and reduced heart function have been recently reported. We tested the effects of acute antioxidants on arterial endothelial function, PAP and heart function before and after a field dive. Vitamins C (2 g) and E (400 IU) were given to subjects 2 h before a second dive (protocol 1) and in a placebo-controlled crossover study design (protocol 2). Seven experienced divers performed open sea dives to 30 msw with standard decompression in a non-randomized protocol, and six of them participated in a randomized trial. Before and after the dives ventricular volumes and function and pulmonary and brachial artery function were assessed by ultrasound. The control dive resulted in a significant reduction in flow-mediated dilatation (FMD) and heart function with increased mean PAP. Twenty-four hours after the control dive FMD was still reduced 37% below baseline (8.1 versus 5.1%, P = 0.005), while right ventricle ejection fraction (RV-EF), left ventricle EF and endocardial fractional shortening were reduced much less (approximately 2-3%). At the same time RV end-systolic volume was increased by 9% and mean PAP by 5%. Acute antioxidants significantly attenuated only the reduction in FMD post-dive (P < 0.001), while changes in pulmonary artery and heart function were unaffected by antioxidant ingestion. These findings were confirmed by repeating the experiments in a randomized study design. FMD returned to baseline values 72 h after the dive with pre-dive placebo, whereas for most cardiovascular parameters this occurred earlier (24-48 h). Right ventricular dysfunction and increased PAP lasted longer. Acute antioxidants attenuated arterial endothelial dysfunction after diving, while reduction in heart and pulmonary artery function were unchanged. Cardiovascular changes after diving are not fully reversed up to 3 days after a dive, suggesting longer lasting negative effects.

Administration, Oral↗
PubMed1991

[Structure of the endotheliocytes of cerebral vessels of aquatic mammals].

By means of scanning microscopy the relief of luminal surface of endotheliocytes, lining microvessels of various parts of the brain in the Pusa sibirica, Phoca vitulina and Delphinapterus leucas have been studied. Specialized formations of the cellular surface--various processes, projections, toruli have been revealed; their character in various parts of the brain in diving animals is determined by the blood stream conditions and their different sensitivity to oxygen deficiency during diving. The peculiarities, revealed in the structure of the cerebral vessels intima, are considered as one manifestations of the adaptive properties in the organism of diving animals, which had been developed in them during the process of a long evolution, while they adapted to the aquatic environment.

Adaptation, Physiological↗
PubMed1992

[Arrhythmia in athletes during length diving].

On diving at a distance of 50 m by arresting their breathing, some male athletes were shown to develop cardiac arrhythmias which occurred at min 2 of a restorative period and entirely disappeared at the end of the second-fifth min. It is essential to make further studies of the impact of diving on the cardiac rhythm in athletes in order to elucidate how these disturbances should be regarded: abnormal or physiological.

Adolescent↗
PubMed1998

Ontogenesis of the sperm whale brain.

The development of the sperm whale brain (Physeter macrocephalus) was investigated in 12 embryos and early fetuses to obtain a better understanding of the morphological and physiological adaptations in this most exotic cetacean concerning locomotion, deep diving, and orientation. In male adult sperm whales, the average absolute brain mass and the relative size of the telencephalic hemisphere are the largest within the mammalia, whereas the ratio of the brain mass to the total body mass is one of the smallest. In the early sperm whale fetus, the rostral part of the olfactory system (olfactory nerves and bulbs) is lost, whereas the nervus terminalis seems to persist. Several components of the limbic system show signs of regression (hippocampus, fornix, mamillary body). In contrast, some components of the auditory system (trapezoid body, inferior colliculus) show marked enlargement in the early fetal period, thereby reflecting their dominant position in the adult. The cerebellum and pons grow slower than in most smaller toothed whales. The pyramidal tract develops poorly (reduction of the limbs), whereas marked growth of the striatum and inferior olive may be related to the animal's locomotion via trunk and tail. In the early fetal period, the trigeminal, vestibulocochlear, and facial nerves are the dominant cranial nerves (besides the vagus nerve). Whereas the number of axons in the vestibulocochlear nerve is high in adult, toothed whales and their diameters are considerable, the trigeminal nerve of the sperm whale may be the thickest of all cranial nerves and has the largest number of axons (innervation of the huge forehead region). A similar situation seems to exist for the facial nerve: It innervates the blowhole musculature that surrounds the very large spermaceti organ and melon (generation and emission of sonar clicks).

Animals↗
PubMed2003

The development of diving bradycardia in bottlenose dolphins (Tursiops truncatus).

Bradycardia is an important component of the dive response, yet little is known about this response in immature marine mammals. To determine if diving bradycardia improves with age, cardiac patterns from trained immature and mature bottlenose dolphins ( Tursiops truncatus) were recorded during three conditions (stationary respiration, voluntary breath-hold, and shallow diving). Maximum (mean: 117+/-1 beats.min(-1)) and resting (mean: 101+/-5 beats.min(-1)) heart rate (HR) at the water surface were similar regardless of age. All dolphins lowered HR in response to apnea; mean steady state breath-hold HR was not correlated with age. However, the ability to reduce HR while diving improved with age. Minimum and mean steady state HR during diving were highest for calves. For example, 1.5-3.5-year-old calves had significantly higher mean steady state diving HR (51+/-1 beats.min(-1)) than 3.5-5.5-year-old juveniles (44+/-1 beats.min(-1)). As a result, older dolphins demonstrated greater overall reductions in HR during diving. Longitudinal studies concur; the ability to reduce HR improved as individual calves matured. Thus, although newly weaned calves as young as 1.7 years exhibit elements of cardiac control, the capacity to reduce HR while diving improves with maturation up to 3.5 years postpartum. Limited ability for bradycardia may partially explain the short dive durations observed for immature marine mammals.

Age Factors↗
PubMed2001

Ventilatory responses to hypercapnia in divers and non-divers: effects of posture and immersion.

The aim of this study was to determine the effects on respiratory drive of two factors, one mechanical (lung volume) and one chemical (sensitivity to hypercapnia), that are involved in determining the breath-hold duration (BHD). Functional residual capacity was measured by helium dilution with the subject seated in air, seated in water and in the prone position in water. Hyperoxic hypercapnia rebreathing (Read's method) was carried out under identical environmental conditions to assess the effects of CO2 pressure on respiratory centre output by measuring ventilation, mean inspiratory flow and occlusion pressure. Sixteen healthy volunteers were tested. 8 trained divers and 8 non-divers. Functional residual capacity decreased for the postures seated in water (30.8%-34.8%) and for prone position in water (20.3%-20.9%) when compared to the posture seated in air (P<0.0001), all subjects pooled. No difference was found between groups. The slopes of the linear regression, which characterised the sensitivity to CO2 and were determined with the rebreathing tests, revealed differences between the two populations (ventilation: P < 0.0001; mean inspiratory flow: P < 0.05). No difference was found for occlusion pressure or between the different postures. These results confirmed a lower sensitivity to CO2 for trained divers. This adaptation was shown to decrease respiratory centre activity at the origin of the breath-hold breaking point. The immersion, did not influence respiratory drive, despite a decrease in lung volumes. The authors suggest that these findings may be explained by a specific apnoea training and a pronounced bradycardia in immersion.

Adaptation, Physiological↗
PubMed2001

Breath-holding time: effects of non-chemical factors in divers and non-divers.

Two main factors (chemical and non-chemical factors) are involved in the determination of breath-holding time (BHT). Earlier studies have shown that chemical factors can be modified by training. The aim of this study was to establish whether BHT can be lengthened or shortened by changes in non-chemical factors according to the degree of training of the divers. Hyperoxic hypercapnic rebreathing challenges interrupted by different periods of voluntary apnoea (20, 40 and 50 s) were performed by divers (n=8) and non-divers (n=6). The relationships between ventilation (VE) and end-tidal PCO2 and mean inspiratory flow (VT/TI) where VT is the tidal volume and TI the inspiration time) and end-tidal PCO2 were measured before (pre) and after (post) apnoea for each population. The slopes of these linear regressions (VEs and VT/TI,s, respectively) reflected respiratory centre activity. VFs-post and VT/TIs-post increased with BHT and were higher in the non-divers than in divers. There were no significant differences between VFs-pre and VFs-post or between VT/TIs,-pre and VT/TIs-post in divers for all BHT. However, in non-divers, significant differences between pre and post values appeared at 20, 40 and 50 s for VT/TI,s and at 40 and 50 s for VEs. Non-chemical factorswere obtained by calculating the differences between pre and post values and were different at 20 and 40 s for VEs (P<0.05) and for all BHT for VT/TI,s (P<0.05). The non-chemical factors increased significantly with BHT and were higher in the non-divers. These adaptations in divers may modify the breath-hold breaking point and consequently increase BHT.

Adaptation, Physiological↗
PubMed2005

The development of the pulmonary surfactant system in California sea lions.

Pulmonary surfactant has previously been shown to change during development, both in composition and function. Adult pinnipeds, unlike adult terrestrial mammals, have an altered lung physiology to cope with the high pressures associated with deep diving. Here, we investigated how surfactant composition and function develop in California sea lions (Zalophus californianus). Phosphatidylinositol was the major anionic phospholipid in the newborn, whereas phosphatidylglycerol was increased in the adult. This increase in phosphatidylglycerol occurred at the expense of phosphatidylinositol and phosphatidylserine. There was a shift from long chain and polyunsaturated phospholipid molecular species in the newborn to shorter chain and mono- and disaturated molecular species in the adult. Cholesterol and SP-B concentrations were also higher in the adult. Adult surfactant could reach a lower equilibrium surface tension, but newborn surfactant could reach a lower minimum surface tension. The composition and function of surfactant from newborn California sea lions suggest that this age group is similar to terrestrial newborn mammals, whereas the adult has a "diving mammal" surfactant that can aid the lung during deep dives. The onset of diving is probably a trigger for surfactant development in these animals.

Animals↗
PubMed2000

Technique and timing in the womens forward two and one half somersault pike and mens three and one half somersault pike 3m springboard dives.

The purpose of this study was to compare the forward two and one half somersault dive in a pike position (105B) performed by females (n=25) and the forward three and one half somersault dive in a pike position (107B) performed by males (n=25) to determine changes required by females to successfully perform 107B. Video data of the dives performed at the 1999 FINA World Diving Cup were captured and digitised to obtain times and postures of the divers at specific events including hurdle landing, takeoff, and entry. Estimates of hurdle flight height and mass-normalised work done on the springboard were obtained from hurdle and flight times. Females performing 105B had significantly less hip and knee flexion at landing from the hurdle than males performing 107B. It is known from simulations that the ability to land in a very flexed position without absorbing energy depends on the ability to generate large extension torques at landing. Therefore, it is likely that females need to increase strength to successfully complete 107B.

Adolescent↗
PubMed1984

Ultrasonic monitoring of decompression procedures.

p6rly detection of bubbles may provide clues to the mechanism of their formation, and a knowledge of their extent during a decompression may allow the prevention of decompression sickness. We have used ultrasound imaging to study bubble formation in peripheral tissues. The results suggest that: (a) a threshold supersaturation for bubble formation exists; (b) the earliest bubbles are intravascular; (c) before signs of decompression sickness a substantial accumulation of stationary bubbles occurs. Despite the success of Doppler methods in detecting moving bubbles after decompressions normally considered safe, recent studies have shown that the correlation between number of bubbles detected and symptoms of decompression sickness is often poor. We have used a time integral of the ultrasound images, which avoids laborious image analysis, to follow the extent of both moving and stationary bubbles. Human trials involving a wide variety of decompressions suggest that correct prediction of symptoms is possible.

Animals↗
PubMed2004

In situ cardiac performance of Pacific bluefin tuna hearts in response to acute temperature change.

This study reports the cardiovascular physiology of the Pacific bluefin tuna (Thunnus orientalis) in an in situ heart preparation. The performance of the Pacific bluefin tuna heart was examined at temperatures from 30 degrees C down to 2 degrees C. Heart rates ranged from 156 beats min(-1) at 30 degrees C to 13 beats min(-1) at 2 degrees C. Maximal stroke volumes were 1.1 ml x kg(-1) at 25 degrees C and 1.3 ml x kg(-1) at 2 degrees C. Maximal cardiac outputs were 18.1 ml x kg(-1) min(-1) at 2 degrees C and 106 ml x kg(-1) min(-1) at 25 degrees C. These data indicate that cardiovascular function in the Pacific bluefin tuna exhibits a strong temperature dependence, but cardiac function is retained at temperatures colder than those tolerated by tropical tunas. The Pacific bluefin tuna's cardiac performance in the cold may be a key adaptation supporting the broad thermal niche of the bluefin tuna group in the wild. In situ data from Pacific bluefin are compared to in situ measurements of cardiac performance in yellowfin tuna and preliminary results from albacore tuna.

Adaptation, Physiological↗
PubMed2000

Sub-ice foraging behavior of emperor penguins.

Emperor penguins (Aptenodytes forsteri) were equipped with a remote underwater video camera, the Crittercam, to evaluate sub-ice foraging behavior while the birds dived from an isolated dive hole. Three birds dived and foraged successfully for 1 h periods after being trained to wear and to dive with a harness for camera attachment. Video and depth profile recordings revealed that emperor penguins travel at shallow depths (<50 m), ascend to the undersurface of the ice to feed on fish, and descend back to depth to return to the exit hole. Although the mean durations of dives of individual birds with the Crittercam were 21-35 % shorter than the diving durations of these same birds without the camera, the dive profiles in both situations were similar, thus demonstrating a similar foraging strategy in birds diving without the camera. Despite shorter diving durations with the camera, the penguins were still successful at prey capture in 80 % of 91 dives greater than 1 min in duration. Prey included the sub-ice fish Pagothenia borchgrevinki. Hunting ascents (from depth to within 5 m of the surface) occurred in 85 % of dives, ranged from zero to three per dive, and were associated with successful prey capture in 77 % of 128 ascents. Occasionally, several fish were captured during a single ascent. These observations and this application of video technology create a model for further physiological and behavioral studies of foraging, and also emphasize the potential importance of shallow dives as sources of food intake for emperor penguins during foraging trips to sea.

Animals↗