Human Divers Research Articles

Pressure reversed extracellular striatal dopamine decrease produced by d 1 receptor agonist SKF 38393, and D 2 receptor agonist LY 171555, but failed to change the effect of the activation of both D 1 and D 2 receptors

When human divers or experimental animals are exposed to high pressure, they develop the high-pressure neurological syndrome which is characterized by electroencephalographic changes and behavioral disturbances. Recently, neurochemical disorders such as a pressure-induced increase in dopamine release have been demonstrated. In the present study, pharmacological experiments, using dopamine receptor agonists such as D 1 receptor agonist SKF 38393, D 2 receptor agonist LY 171555 and D 1/D 2 receptor agonist apomorphine, were performed to investigate dopamine receptor function at the neurochemical level. Only apomorphine and mixed SKF 38393 + LY 171555 prevented the pressure-induced increase in dopamine release while SKF 38393 or LY 171555 administered alone failed to do so. The results suggest that the D 1-D 2 link would be reduced under high pressure because of an abnormal function of D 1 receptors which would allow high-affinity D 2 states for dopamine. If so, such a preponderance of high-affinity states in D 2 postsynaptic receptors could be associated with hyperbaric hyperlocomotor activity. Elsewhere, results also suggested that the pressure-induced disorders in dopamine receptor function could be involved in the pressure-induced elevation in dopamine release.

A hypothesis regarding possible interactions between the pressure-induced disorders in dopaminergic and amino-acidergic transmission

When human divers or experimental animals are exposed to high pressure they develop the high pressure neurological syndrome (HPNS). The main symptoms include electroencephalographic changes and behavioral disturbances such as tremor, myoclonia, and hyperlocomotor activity. Recently, pressure-induced disorders in dopaminergic and amino-acidergic neurotransmission have been reported. In the present theoretical study, we review in vitro and in vivo neurochemical, electrophysiological, and pharmacobehavioral evidence concerning alterations in dopaminergic, glutamatergic, and GABAergic transmission occurring at high pressure, and their possible relationship to the symptoms of HPNS. Moreover, we also examine data concerning interactions, at normal pressure, between dopaminergic, glutamatergic, and GABAergic transmission that we suggest they could apply equally under high pressure between the pressure-induced disorders in dopaminergic and amino-acidergic transmission.

Effects of the administration of a-methyl-p-tyrosine on the striatal dopamine increase and the behavioral motor disturbances in rats exposed to high pressure

When human divers and experimental animals are exposed to increased environmental pressure, they develop the high pressure neurological syndrome (HPNS). Moreover, it has been recently demonstrated that pressure exposure induced an increase in striatal dopamine (DA) release. In this study, the effects of intracerebroventricular administration of a-methyl-p-tyrosine on the pressure-induced striatal DA increase, and the behavioral motor disturbances of HPNS, including hyperlocomotor activity (HLA), tremor, and myoclonia were monitored in free-moving rats. Striatal DA release was monitored by in vivo voltammetry, and behavioral symptoms using piezoelectrical sensors. Results suggested that the pressure-induced striatal DA increase could be the consequence of a release in both newly synthesized and vesicular DA. Elsewhere, data also confirmed that the pressure-induced DA disturbances would be involved in the development of HLA.

Role of dopamine receptors in the occurrence of the behavioral motor disturbances in rats exposed to high pressure

When human divers and experimental animals are exposed to an increasing environmental pressure, they develop the high pressure neurological syndrome (HPNS) characterized by electroencephalographic changes and sleep and behavioral disturbances. In rats, behavioral disturbances essentially include hyperlocomotor activity (HLA), tremor and myoclonia. Moreover, HLA has recently been demonstrated to be linked to a pressure-induced striatal increase of dopamine (DA). In these experiments, it was proposed to investigate in rats, at the behavioral level, the role of DA receptors in the occurrence of the pressure-induced DA disturbances. DA receptor agonists were found to induce no significant changes in the development of HLA, tremor, and myoclonia. Alternatively, HLA was found to be dramatically antagonized by the use of DA receptor antagonists (SCH 23390, sulpiride, and haloperidol), while tremor and myoclonia only decreased in SCH 23390 experiments.

Dopamine increase in the nucleus accumbens of rats exposed to high pressure.

When human divers and experimental animals are exposed to high pressure, they develop the high pressure neurological syndrome (HPNS) characterized by electroencephalographic changes, sleep and behavioral disturbances. Free-moving rats chronically implanted in the nucleus accumbens with carbon electrodes essentially selective to dopamine (DA) were compressed to 80 bar. Compression was found to lead to a sustained increase in extracellular DA level (+88%), then during the stay and decompression phases, values progressively decreased. These results are discussed in the field of the involvement of the DA meso-limbic pathways in the occurrence of some of the behavioral disturbances of HPNS in rats including hyperlocomotor activity and hoarding behavior.

Multisensor visualization for underwater archaeology

The problems particular to underwater archaeology are discussed. The underwater archaeology study of three sunken ships is then described. They are the USS Monitor, Hamilton and Scourge. Future prospects with respect to improved technology are indicated. From depths prohibitive to human divers, remotely operated vehicles (ROVs) send back acoustic and optical data to archaeologists safe and comfortable aboard ship. Sonars give the big picture, and acoustic data can be processed to extract spatial information: shape and relative placement of artifacts. Still cameras and video document fine-scale features, allowing an archaeologist to identify and date underwater relics. New computational and graphics technologies afford scientists and engineers a visual means of digesting the massive information flow from state-of-the-art ROVs. >

Quantitative Study of Behavioral Disturbances in Rats Exposed to High Pressure.

When human divers or experimental animals are exposed to high pressure, they develop the High Pressure Neurological Syndrome (HPNS). Male Sprague-Dawley rats were exposed to high pressure in a conventional helium-oxygen breathing mixture to 80 bars. Pressure-induced behavioral motor disturbances including hyperlocomotor activity (HLA), tremor and myoclonia were monitored with a noninvasive piezoelectrical sensor device enabling a without discontinuity long-term analysis. New data were obtained on the development of the HPNS behavioral motor disturbances. Indeed, the present results suggest myoclonia would be more sensitive to constant high pressure exposure, while HLA and tremor would be more sensitive to increasing pressure. Moreover, myoclonia were found to occur significantly later in rats which developed epileptic seizures than in other. The present results constitute the quantitative basis of HPNS motor disturbances for future pharmacological pressure experiments.

Splenic contraction during breath-hold diving in the Korean ama

Major increases of hemoglobin concentration and hematocrit, possibly secondary to splenic contraction, have been noted during diving in the Weddell seal. We sought to learn whether this component of the diving response could be present in professional human breath-hold divers. Splenic size was measured ultrasonically before and after repetitive breath-hold dives to approximately 6-m depth in ten Korean ama (diving women) and in three Japanese male divers who did not routinely practice breath-hold diving. Venous hemoglobin concentration and hematocrit were measured in nine of the ama and all Japanese divers. In the ama, splenic length and width were reduced after diving (P = 0.0007 and 0.0005, respectively) and calculated splenic volume decreased 19.5 +/- 8.7% (mean +/- SD, P = 0.0002). Hemoglobin concentration and hematocrit increased 9.5 +/- 5.9% (P = 0.0009) and 10.5 +/- 4% (P = 0.0001), respectively. In Japanese male divers, splenic size and hematocrit were unaffected by repetitive breath-hold diving and hemoglobin concentration increased only slightly over baseline (3.0 +/- 0.6%, P = 0.0198). Splenic contraction and increased hematocrit occur during breath-hold diving in the Korean ama.

Man as a breath-hold diver

There are many thousands of both recreational and professional divers daily engaged in breath-hold diving throughout the world. The most widely known breath-hold divers are found among males and females in Japan and Korea, collectively called the ama. However, compared with many diving animals, man's ability as a breath-hold diver is very much limited. The average duration of a dive is 30–60 s, although one can dive for a period of up to 2–3 min. Usual depths of dive are 5–20 m. However, Jacques Mayol dove to 105 m in 1983, setting a new world record. It is still not clearly understood how one can reach such a depth without developing a pulmonary "squeeze." Human divers also display a mild but significant diving bradycardia which is often accompanied by cardiac arrhythmias. Although the cardiac output decreases slightly, the arterial blood pressure increases during breath holding. It has been suggested, but not unequivocally demonstrated that these cardiovascular changes observed during diving in man subserve to conserve O2 as in diving animals. Human divers descend to the bottom while retaining a considerable amount of air in the lung, thus allowing diffusion of N2 into the blood. As a result, human breath-hold divers can develop decompression sickness if they dive to deeper depths frequently enough. The major limiting factor for human divers is the loss of body heat to the surrounding medium (water) which has a high thermoconductivity. The subcutaneous fat thickness of human divers is much less than that in diving animals and thus human divers are at a great disadvantage. Although repetitive exposures to cold water stress are known to induce a significant cold acclimatization in man, these changes are rather ineffective in prolonging cold water diving time.

Aerial maneuvers of leaping lemurs: The physics of whole-body rotations while airborne.

Several prosimian species begin a leap from a vertical support with their back toward the landing target. To reorient themselves from this dorsally facing, head-first lift-off to a ventrally facing, feet-first landing, the animals combine an initial twist with a partial backward somersault. Cinefilms of a captive colony of ringtailed lemurs (Lemur catta) revealed that during leaps from vertical poles to horizontal supports, the backward somersaulting rotations were often initiated while the animals were airborne. How could these prosimians initiate rotations in the absence of externally applied forces without violating angular momentum conservation? The problem was approached through vector analysis to demonstrate angular momentum (H) changes about the three principal (symmetrical) axes of rotation for a series of critical body positions that were extracted from the filmed sequences. One L. catta specimen was segmented to provide the dimensions and weights necessary for modeling the various body positions. These data were also used to calculate moments of inertia about the three principal axes in order to predict if rotations about these axes were stable or metastable. Lemurs, like any projectile, must conserve the total angular momentum (HT ) established at lift-off. HT , however, is a vector quantity that is the resultant of component vectors about the three principal axes. Thus, H about the individual axes may change as long as HT remains constant. Strategically timed tail movements tilted the body, thereby changing the H value about the head-to-toe (twisting) axis. To conserve HT , also aligned along the twisting axis, angular momentum transferred to the somersaulting axis. Owing to the direction of tail-throw, the initiated rotations were partial backward somersaults that brought the hindlimbs forward for landing. This strategy for initiating specific rotations parallels that practiced by human springboard divers.

Hyperbaric diuresis and nocturia--a review.

Human divers are now able to engage in a multi-day dive to a considerable depth using the mixed gas saturation diving technique, however their daily activities are somewhat limited in the depth. One of the major problems that has not been generally appreciated is the potential for body fluid disturbances at high pressure due to the development of a sustained diuresis. In addition, a marked nocturia has been observed in recent saturation dives at 26-31 atmospheres absolute (ATA), which disturbs divers' sleep during the night. In this review, we will briefly discuss the basic characteristics and mechanisms of these disturbances of renal functions observed during hyperbaric exposure.

A Review of Recent Research on Supervisory Control of Deep Ocean Robotic Vehicles and Manipulators

This paper reviews recent research in the MIT Man-Machine Systems Laboratory on the use of computer aiding to a human operator in both issuing commands to and feedback sensing and display from a semi-intelligent deep ocean vehicle/manipulator. The motivation for such systems is to replace human divers in very deep and extensive inspection and work operations, which tend to be very hazardous and costly. However there are advantages to retaining the human operator as a supervisory controller, i.e., where an operator, safe on the ocean surface, intermittently communicates to a remote vehicle's computer the appropriate subgoal's and contingency information, and the computer interprets and executes the commands with the help of the vehicles own sensors.

Diving reflex. Another method of treating paroxysmal supraventricular tachycardia.

Bradycardia during submersion has long been known to occur in diving animals.1,2This diving reflex is initiated through a complex cardiovascular reflex partly through cold water stimulation of afferent nerve endings on the body and partly by apnea.3,4Apnea alone causes similar but much less extreme cardiovascular response. The efferent limb of the reflex is mediated through increased sympathetic stimulation of peripheral vasculature (except in heart and brain), which causes vasoconstriction and intense vagal stimulation of the heart. This reflex mechanism prominently seen in aquatic animals allows them to slow their heart rate, decrease oxygen demand, increase oxygen extraction, redistribute blood flow, and maintain arterial pressure when submerged.5Though in a less intense form, man has retained this reflex. Bradycardia is commonly observed in human divers when they are submerged in water.6This reflex is attenuated by a reduction in water temperature7,8and can be

Habitat selection and territorial defense behaviors in juvenile cortez angelfish, Pomacanthus zonipectus (gill)

Scuba diving observations in the Gulf of California (Mexico) on juvenile Cortez angelfishes, Pomacanthus zonipectus (Gill), indicate that these fish select and defend territories centered about a rock crevice. By day, they make brief feeding excursions, venturing even over open sandy areas near the rocks. They are substrate feeders, and will remove ectoparasites from other fishes, even attempting to ‘clean’ human divers. At night they remain in their rock crevices. Laboratory experiments, conducted to quantify habitat-selection and territorial-defense behaviors in juvenile P. zonipectus, revealed that they spend 75% of their time during the day near rocks and 25% over sand in a divided experimental tank. The frequency of attacks on a mirror image increased as the mirror was moved closer to the rock crevice which was the territorial focus.

On the Field Study of Shark Behavior

The difficulties of observational study of active, wide-ranging sharks in the relatively concealing natural underwater environment are discussed for both baited and non-baited situations. The possible technique of habituating sharks to the diver's presence is considered in view of the logistical and safety problems imposed by the physical limitations of unaided, unprotected human divers. It is concluded that previous sharkobservation methods are inadequate, and that supplementary study techniques must be developed and emphasized. These include remote monitoring by ultrasonic telemetry, telemetry-aided direct observation, and the use of miniature submersibles designed specifically for shark observation.

Serum hexosaminidase activity in man under simulated diving conditions (38523).

The activities of serum hexosaminidases from human divers before, during and after simulated dives was measured. Decreases in hexosaminidase A activities were observed in the 1000 FSW saturation dive, whereas an increase in hexosaminidase A activity was observed during decompression in the subsaturation dives at 400 FSW and 650 FSW.

Considerations of the pathophysiology and histopathology of deafness associated with decompression sickness and absence of middle-ear barotrauma

Dr. J. Donald Harris has previously speculated in the literature that, based on clinical impressions, a group of Navy Divers with post-dive deafness and/or vestibular attacks may have suffered inner-ear hemorrhage. We have found hemorrhage in the inner ear of a guinea pig sacrificed 16 days after a post-dive vestibular attack with cochlear potential function loss. In terms of potential treatment for human divers it is important to determine how soon after the onset of an attack inner-ear hemorrhage can occur. We now have an additional guinea pig with a severe post-dive cochlear potential loss which was sacrificed for histology at 21 hours post-dive. This animal shows a plasma exudate in the inner ear, but no red cells are present. The similarity of these two pathology cases to the results of sympathetic nervous system stimulation by Seymour and Tappin reported in 1953 is discussed. We also consider the possibility that hypercoagulation, embolic, and thrombotic problems may be involved in the etiology of the diving-deafness syndrome. Preliminary results of post-diving deafness treatment with urokinase and urokinase plus heparin are also discussed.

Imitative Behaviour By Indian Ocean Bottlenose Dolphins (t uRsiops Aduncus) in Captivity

Evidence is presented for the ability of Indian Ocean bottlenose dolphins (Tursiops aduncus) to learn complex behavioural sequences by observation and to imitate a wide variety of previously unfamiliar motor patterns and sounds, without any apparent external reinforcement apart from the performance of the activity itself, both in the presence and in the absence of the stimulus which originally evoked the imitative behaviour. The reproduction in fine detail by a dolphin of the comfort and sleeping movements of a Cape Fur Seal (Arctocephalus pusillus), leading to behavioural interactions between the two forms with attempts at copulation, and culminating in aggression is described. Further instances of observational learning are cited, including the imitation by dolphins of the activities and sounds of human divers during maintenance operations in the pool which resulted in elementary tool-using behaviour by the dolphins. Interactions between dolphins and seals occurred not only in captivity but also under free-ranging conditions. The significance of imitation in delphinids for comparative assessments of animal intelligence is discussed and the possible function under normal conditions of the delphinid faculty to imitate is considered. It is proposed that the tendency to imitate may be genetically programmed in delphinids to operate in the selection of compatible sexual partners, in the reinforcement of social bonds and in the strengthening of group cohesiveness.

United States Navy to use underwater television to safeguard human divers

United States Navy to use underwater television to safeguard human divers