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PubMed1987

Pulmonary function of the green sea turtle, Chelonia mydas.

Lung volumes, oxygen uptake (VO2), end-tidal PO2, and PCO2, diffusing capacity of the lungs for CO (DLCO), pulmonary blood flow (QL) and respiratory frequency were measured in the green sea turtle (Chelonia mydas) (49-127 kg body wt). Mean lung volume (VL) determined from helium dilution was 57 ml/kg and physiological dead space volume (VD) was about 3.6 ml/kg. QL, determined from acetylene uptake during rebreathing, increased in proportion to VO2 with temperature. Therefore, constant O2 content difference was maintained between pulmonary arterial and venous blood. DLCO, measured using a rebreathing technique, was 0.04 ml X kg-1 X min-1 X Torr-1 at 25 degrees C. Several cardiopulmonary characteristics in C. mydas are advantageous to diving: large tidal volume relative to functional residual capacity promotes fast exchange of the alveolar gas when the turtle surfaces for breathing: and the concomitant rise of pulmonary blood flow and O2 uptake with temperature assures efficient O2 transport regardless of wide temperature variations encountered during migrations.

Animals↗
PubMed1995

Effects of the submarine environment on renal-stone risk factors and vitamin D metabolism.

The effects of total sunlight deprivation on urinary risk factors for nephrolithiasis and vitamin D metabolism were studied in 20 healthy male subjects. Blood and 24-h urine samples were collected before submarine deployment and 68 days later while still at sea. No subject received sunlight exposure during the test interval. Significant decreases in daily urinary excretion of calcium, uric acid, sodium, sulfate, and phosphorus were found. The relative supersaturation ratio of monosodium urate also fell. There was no change in urinary citrate or urine volume. Mean serum levels of 25-hydroxyvitamin D [25(OH)D] declined from 31 to 19 pg/ml (P < 0.0001), parathyroid hormone increased from 22 to 30 pg/ml (P < 0.0001), and osteocalcin (GLA) increased from 2.7 to 3.3 ng/ml (P = 0.005). Mean serum levels of 1,25 dihydroxy-vitamin D were unchanged. Four subjects had 25(OH)D levels below 10 ng/ml by the end of the submarine patrol. These findings suggest that exposure to the submarine environment produces physiologic changes that decrease the risk for renal stone formation. The data are consistent with the role of vitamin D metabolism in sunlight deprivation and demonstrate that compensatory mechanisms are well established within 68 days.

Adult↗
PubMed2006

The evolution of colony-level development in the Siphonophora (Cnidaria:Hydrozoa).

Evolutionary developmental biology has focused almost exclusively on multicellular organisms, but there are other relevant levels of biological organization that have remained largely neglected. Animal colonies are made up of multiple physiologically integrated and genetically identical units called zooids that are each homologous to solitary, free-living animals. Siphonophores, a group of pelagic hydrozoans (Cnidaria), have the most complex colony-level organization of all animals. Here the colony-level development of five siphonophore species, strategically sampled across the siphonophore phylogeny, is described from specimens collected using deep-sea submersibles and by self-contained underwater breathing apparatus diving. These species include three cystonects, Bathyphysa sibogae, Rhizophysa filiformis, and Rhizophysa eysenhardti, and two "physonects", Agalma elegans and Nanomia bijuga. These data, together with previous findings, are analyzed in a phylogenetic framework to reconstruct key features of the history of colony-level organization and development in the Siphonophora. It is shown that gonodendra and gastrozooids of the examined cystonects arise as independent buds directly on the stem, whereas probud subdivision (the origin of feeding, reproductive, and other zooids from a single bud) is a synapomorphy of the Codonophora. The origin of probud subdivision is associated with the origin of cormidia as integrated units of colony organization, and may have allowed for greater morphological and ecological diversification in the Codonophora relative to the Cystonectae. It is also found that symmetry is labile in siphonophores, with multiple gains and/or losses of directional asymmetry in the group. This descriptive work will enable future mechanistic and molecular studies of colony-level development in the siphonophores.

Animals↗
PubMed1992

[Work history, health conditions and hearing loss of Ishigaki fishermen].

Based on our previous health survey among Ishigaki fishermen in 1979, this study aimed at clarifying the relations of their work histories to physical characteristics, physiological functions, blood conditions and hearing levels. Medical examination was conducted in 1987 on 118 fishermen inclusive of 33 followed-up fishermen, and in 1989 noise-level and noise-induced temporary threshold shift of hearing was measured for different fishing methods. The results were as follows; 1) Fishing history was not specifically associated with any physical characteristics. 2) High HDL cholesterol, which was observed among divers using diving apparatus, was considered to be a survival effect for divers, since HDL cholesterol is amplified by intensive muscle work. 3) Abnormalities of ECG except for a high R wave were notably observed among the divers, who once changed from unassisted diving to diving with apparatus and then to fishing lines. The main reason for switching jobs was claimed to be caisson disease, and it was suggested that diving with apparatus was related to a high risk of health hazards in the central nervous system and/or respiro-circulatory system. 4) Acoustic acuity greatly declined with aging, and which was commonly observed in groups with different work histories. By way of explanation, exposure to ship engine sounds during daily travelling was the most likely cause. It was also revealed that several hours' exposure to the engine sounds was needed to detect a temporary threshold shift of hearing before and after work.

Cardiovascular Diseases↗
PubMed1977

Dyspnea in divers at 49.5 ATA: mechanical, not chemical in origin.

Pulmonary function was studied in six divers living in a hyperbaric chamber at a pressure nearly fifty times normal (49.5 atmospheres absolute (ATA), equivalent to 488 m or 1600 ft seawater (fsw)). As expected, ventilatory function was reduced. At 49.5 ATA, maximum voluntary ventilation (MVV) was 45% less than the control value. Instantaneous rates of gas flow during forced expiration were similarly reduced, especially those flow rates measured high in the lung volume. These reductions occurred despite an apparent increase in functional residual capacity (FRC) and the use of transpulmonary pressures considerably greater than those exerted during the same maneuvers at normal (sea-level) pressure. During underwater work at 49.5 ATA, the divers rapidly became exhausted at moderate levels of oxygen consumption (1.9 liters/min), showing severe dyspnea and impending syncope. These symptoms were not due to retention of carbon dioxide, nor to hemodynamic or metabolic causes. Thus, dense gas breathing, like asthma, exemplifies a state in which severe dyspnea may occur with normal or low arterial carbon dioxide and normal oxygen transport. The physiological adjustments the divers employed were similar to those seen in acute asthma, imposing an elastic load in addition to the flow-resistive work of breathing a gas mixture eight times as dense as air. Although men can do moderate work under conditions similar to those of this experiment, they will have only a limited physiological reserve available to meet the possibilities of emergencies or respiratory infections.

Adult↗
PubMed1999

Neonatal tolerance to hypoxia: a comparative-physiological approach.

Newborn mammals exhibit a number of physiological reactions which differ from normal adult physiology and are often regarded as signs of immaturity. However, when looked upon from a comparative point of view, it becomes obvious that some of these 'physiological peculiarities' bear striking similarity to adaptation mechanisms known from hypoxia-tolerant animals and may thus contribute to the well-established, yet poorly understood, phenomenon of neonatal hypoxia tolerance. As the mammalian fetus lives at oxygen partial pressures corresponding to 8000 m altitude, the first line of perinatal hypoxia defense consists of long-term adaptations to limited intrauterine oxygen supply: (1) improved O2 transport by fetal acclimatization to high altitude, (2) reduced metabolic rate by hibernation-like deviation from metabolic size allometry, (3) diminished cerebral vulnerability by functional analogies to diving turtle brain, and (4) enhanced metabolic flexibility by optional repartitioning of energy supply from growth to maintenance metabolism. In the case of birth asphyxia, these background mechanisms are complemented by short-term responses to acute oxygen lack: (1) reduction of body temperature as in natural torpor, (2) reduction of heart rate and redistribution of circulation as in diving mammals, (3) reduction of respiration rate typical of 'hypoxic hypometabolism', and (4) reduction of blood pH according to the concept of 'acidotic torpidity'. Although anaerobic metabolism is improved in neonatal mammals by increased glycogen stores, reduced metabolic demands, and sustained wash-out of acid metabolites, neonatal hypoxia tolerance seems to be primarily based on the ability to maintain tissue aerobiosis as long as possible. This is even reflected by isoenzyme patterns which do not consistently favour anaerobic glycolysis and, thus, are reminiscent of the 'lactate paradox' found in high altitude adaptation. Altogether, from a biological point of view, the perinatal period appears as a source of adaptive mechanisms that can be refound, in varying combinations, in many survival strategies. From a clinical point of view, the interplay of long- and short-term mechanisms offers a novel approach to estimation of the newborn's ability to withstand temporary oxygen lack. However, most of these mechanisms are not unambiguous and, above all, not unlimited in their protective effect so that they do not release obstetricians or neonatologists from their obligation to counteract fetal or neonatal hypoxia without delay.

Adaptation, Physiological↗
PubMedDate not supplied

Impact of externally attached loggers on the diving behaviour of the king penguin.

The impact of relatively small externally attached time series recorders on some foraging parameters of seabirds was investigated during the austral summer of 1995 by monitoring the diving behaviour of 10 free-ranging king penguins (Aptenodytes patagonicus) over one foraging trip. Time-depth recorders were implanted in the abdominal cavities of the birds, and half of the animals also had dummy loggers attached on their backs. Although most of the diving behaviour was not significantly affected by the external loggers (P>0.05), the birds with externally attached loggers performed almost twice as many shallow dives, between 0 and 10 m depth, as the birds without external loggers. These shallow dives interrupted more frequently the deep-diving sequences in the case of birds with external loggers (percentage of deep dives followed by deep dives: 46% for birds with implants only vs. 26% for birds with an external attachment). Finally, the distribution pattern of the postdive durations plotted against the hour of the day was more heterogeneous for the birds with an external package. In addition, these penguins had extended surfacing times between two deep dives compared to birds without external attachments (P<0.0001). These results suggest the existence of an extra energy cost induced by externally attached loggers.

Animals↗
PubMed1997

Acoustic effects of the ATOC signal (75 Hz, 195 dB) on dolphins and whales.

The Acoustic Thermometry of Ocean Climate (ATOC) program of Scripps Institution of Oceanography and the Applied Physics Laboratory, University of Washington, will broadcast a low-frequency 75-Hz phase modulated acoustic signal over ocean basins in order to study ocean temperatures on a global scale and examine the effects of global warming. One of the major concerns is the possible effect of the ATOC signal on marine life, especially on dolphins and whales. In order to address this issue, the hearing sensitivity of a false killer whale (Pseudorca crassidens) and a Risso's dolphin (Grampus griseus) to the ATOC sound was measured behaviorally. A staircase procedure with the signal levels being changed in 1-dB steps was used to measure the animals' threshold to the actual ATOC coded signal. The results indicate that small odontocetes such as the Pseudorca and Grampus swimming directly above the ATOC source will not hear the signal unless they dive to a depth of approximately 400 m. A sound propagation analysis suggests that the sound-pressure level at ranges greater than 0.5 km will be less than 130 dB for depths down to about 500 m. Several species of baleen whales produce sounds much greater than 170-180 dB. With the ATOC source on the axis of the deep sound channel (greater than 800 m), the ATOC signal will probably have minimal physical and physiological effects on cetaceans.

Acoustics↗
PubMed1990

Metabolic reduction in hypothermia: pathophysiological problems and natural examples--Part 1.

Following a description of the protective effects of hypothermia, the limitations resulting from "cold swelling" of the brain, caused by a progressive discrepancy between active and passive cellular transport processes, are discussed. The observation that the tolerable limits of metabolic reduction lie well below the normal turnover rates leads to a short survey of the evolution of energy metabolism. The gradual development of the latter from anaerobiosis to aerobiosis and from poikilothermy to homeothermy apparently provides the background for transient reductions to lower rates which spontaneously occur even in higher vertebrates. As an impressive example of such a natural strategy, the anaerobic survival of diving turtles is outlined which essentially depends on an efficient buffering. This dependence bears analogy to cardioplegia, where an increase in buffering capacity can greatly retard the fall of energy turnover, thus leading, as is shown by microcalorimetry, to an intermediate plateau of anaerobic metabolism.

Adaptation, Physiological↗
PubMed2004

Momentary changes in the cardiovascular autonomic system during mental loading in patients with panic disorder: a new physiological index "rho(max)".

BACKGROUND: Although panic disorder (PD) is suggestive of autonomic nervous system dysfunction, especially in the cardiovascular autonomic system (CAS), the results in many previous studies are still controversial. Using a new physiological index which could well reflect emotional reaction to visual stimuli (Yoshizawa, M., Sugita, N., Tanaka, A., Abe, K., Yambe, T., Nitta, S., 2001. Quantiatative Physioligical Evaluation of Three Dimensional Images. The Seventh International Conference on Virtual Systems and Multumedia, 25-27.), we studied momentary changes in the CAS in patients with PD during audiovisual stimulation (AS) as mental loading. METHODS: During AS, exposed to a video of imaginary experiences such as driving a motor vehicle or diving into the sea, blood pressure (BP) and heart rate (HR) were measured in 12 remitted patients with PD and 19 age- and sex-matched normal controls (NC). We used the maximum cross-correlation coefficient (rho(max)) from the BP to the HR, whose frequency components were limited to around 0.1 Hz. RESULTS: The rho(max) was an available index which could detect the momentary changes in the CAS during AS in both groups. The two-way ANOVA disclosed significant group and time effects on the rho(max). The momentary response to emotional stimuli in the PD patients was slower than that in the NC subjects. LIMITATIONS: Antidepressants have a potential impact on the autonomic variables in this study. CONCLUSIONS: These findings suggest that there may be a dysfunction of the CAS in remitted PD patients and that the dysfunction may be one of the trait markers of PD. To confirm these findings, however, further studies with a large sample size are required.

Acoustic Stimulation↗
PubMed1987

Acute effects of hypercapnia and hypoxia on minute ventilation in unrestrained Weddell seals.

We studied the ventilatory response to hypoxia and hypercapnia in five freely diving juvenile Weddell seals (age = 2 years) at McMurdo Station, Antarctica. The ventilatory response to CO2 was brisk, with minute ventilation increasing as a linear function of end tidal CO2 with an average slope of 3.1 L X (min X mm Hg)-1. The ventilatory response to hypoxia was small and variable. End tidal PO2 values as low as 28 mm Hg provoked at most a doubling of minute ventilation. These results were supported by the observation that elevated end tidal CO2 always inhibited voluntary diving whereas low PO2 values did not. Comparison of the Weddell seals' CO2 responsiveness to that of other mammals reveals similar CO2 sensitivity. We conclude that CO2 is the major determinant of ventilatory drive in wild Weddell seals.

Animals↗
PubMed1993

Environmental hazards and health.

Significant health hazards to the traveller arise from altitude, heat, cold and water. Altitude-induced illness encompasses the benign but common syndrome of acute mountain sickness and also life-threatening pulmonary and cerebral oedema; inadequate acclimatization and rapid ascent are important precipitating factors in each case. Prophylaxis and up to date choices of treatment are discussed in the context of underlying physiological changes. Heat illnesses include exhaustion and heat stroke; they result from increased core temperature and/or physiological responses including peripheral vasodilation and sweating. Preventive measures include acclimatization, ample water without added salt, and matching dress and exercise to the environment. Cold environments pose risk of hypothermia and local cold injury which include frostbite and non-freezing cold injury; as frostnip is only diagnosed after treatment, it is a category of limited usefulness. Prevention of each disorder requires correct clothing and equipment and good training. Other hazards include immersion, and flying too soon after diving.

Altitude Sickness↗
PubMed2002

ACOG committee opinion. Exercise during pregnancy and the postpartum period. Number 267, January 2002. American College of Obstetricians and Gynecologists.

The physiologic and morphologic changes of pregnancy may interfere with the ability to engage safely in some forms of physical activity. A woman's overall health, including obstetric and medical risks, should be evaluated before prescribing an exercise program. Generally, participation in a wide range of recreational activities appears to be safe during pregnancy; however, each sport should be reviewed individually for its potential risk, and activities with a high risk of abdominal trauma should be avoided during pregnancy. Scuba diving also should be avoided throughout pregnancy because the fetus is at an increased risk for decompression sickness during this activity. In the absence of either medical or obstetric complications, 30 minutes or more of moderate exercise a day on most, if not all, days of the week is recommended for pregnant women.

Exercise↗
PubMed2002

ACOG Committee opinion. Number 267, January 2002: exercise during pregnancy and the postpartum period.

The physiologic and morphologic changes of pregnancy may interfere with the ability to engage safely in some forms of physical activity. A woman's overall health, including obstetric and medical risks, should be evaluated before prescribing an exercise program. Generally, participation in a wide range of recreational activities appears to be safe during pregnancy; however, each sport should be reviewed individually for its potential risk, and activities with a high risk of abdominal trauma should be avoided during pregnancy. Scuba diving also should be avoided throughout pregnancy because the fetus is at an increased risk for decompression sickness during this activity. In the absence of either medical or obstetric complications, 30 minutes or more of moderate exercise a day on most, if not all, days of the week is recommended for pregnant women.

Exercise↗
PubMed1985

Effects of inert gas narcosis on behavior--a critical review.

The effects of inert gas narcosis on behavior before unconsciousness are reviewed with particular attention to four issues. The first is whether the qualitative behavioral effects of all inert gases are identical. Evidence is limited but does not contradict an affirmative answer. This is consistent with the unitary hypothesis of narcosis at the physicochemical level. The second issue concerns the relative merits of four approaches to narcosis; (a) the descriptive model, (b) the hierarchical organization hypothesis, (c) the operant paradigm, and (d) the slowed processing model. It is concluded that the latter two are showing some promise. In particular, operant techniques allow more sophisticated measures of narcosis in animals than behavioral end points, such as loss of the righting reflex. The slowed processing model claims that the majority of performance deficits in humans are caused by a single fundamental deficit, slowing of information processing due to decreased arousal. This slowing is usually accompanied by alterations in task strategy. These alterations, in combination with cumulative slowing in working memory, are said to account for the various manifestations of narcosis on complex tasks. The third issue concerns adaptation to narcosis. There is some evidence that adaptation can occur but it is unclear whether the cause is learning specific to narcosis or development of a physiological tolerance. However, adaptation has not always been found and the variables controlling its presence or absence have yet to be identified. The fourth issue concerns the modifying effects of various factors, such as carbon dioxide and anxiety, on narcosis. Methodological and conceptual problems hinder interpretation of the evidence in this area but, contrary to some current views, there appears to be no conclusive evidence that any factor other than ethanol potentiates narcosis. Some implications of these conclusions for diving operations are discussed.

Amphetamine↗
PubMed1994

Neuroepithelial bodies in the lung of Basiliscus vittatus (Reptilia, Iguanidae).

BACKGROUND: Neuro-epithelial bodies (NEB) are corpuscles of currently equivocal function which are present in the lungs of vertebrates. Comparative studies may help to elucidate their role. METHODS: The NEB of Basiliscus vittatus (Reptilia, Iguanidae), a terrestrial lower vertebrate able to dive, are for the first time examined by electron microscopy, immunocytochemistry, and for argyrophilia. RESULTS: Most NEB contain both immunoreactive calcitonin and serotonin but are not labelled with argyrophilia or immunocytochemistry against calcitonin gene-related peptide (CGRP), protein gene product 9.5 (PGP 9.5), or the Leu-7 epitope (Leu-7). Therefore, in NEB of this species, the transcription of the calcitonin/CGRP gene exclusively favors the expression of calcitonin and this is in contrast to the intrapulmonary small neurons. Also, a physiologic difference is expected in the metabolism of ubiquitin in NEB of B. vittatus vs. mammalian NEB and neurons. In addition, the NEB cells are always covered by at least a thin cytoplasmic extension of a neighbouring cell, indicating that luminal contact is not required. Stronger still, it appears that in some lower vertebrates contact to the airspace is avoided. Finally, we provide ultrastructural evidence for the basket-like innervation of NEB in some reptiles. This way of innervation possibly represents an evolutionarily different concept for interaction between NEB corpuscular cells and nerve fibers. CONCLUSIONS: Beyond the confirmation that morphology, content of biologically active substances such as serotonin and calcitonin, and innervation are evolutionary well preserved features of NEB, the results reveal some intriguing features of B. vittatus NEB: strict separation of calcitonin and CGRP, reduced need for the de-ubiquitinating enzyme PGP 9.5, lack of luminal contact, and the basket-like innervation. The latter two properties possibly refer to a mechanoreceptor function of NEB in this species.

Animals↗
PubMed1986

Dysbarism. A review.

This review of dysbarism outlines the development of the knowledge of the effects of pressure changes on tissues and organs, which is related to a complex of physical, physiological and pharmacological changes. It also shows that with the ever increasing pressures to which man is subject the effects can be regarded as total body rather than the traditional concept of a few target organs.

Acute Disease↗
PubMed1982

Comparison of the response of muskrat, rabbit, and guinea pig heart muscle to hypoxia.

Papillary muscles were removed from anesthetized muskrats and rabbits and mounted in a muscle chamber maintained at 29 degrees C. Muscles were stimulated at a rate of 12/min and subjected to 30 min of hypoxia followed by 30 min of reoxygenation. Peak tension in muskrats declined less than peak tension in rabbits during oxygen deprivation. During reoxygenation, peak tension in muskrats rapidly returned to control levels and then exceeded control, whereas peak tension in rabbits never recovered. Time to peak tension was largely unaffected in muskrats during hypoxia and decreased in rabbits. During reoxygenation, time to peak tension increased in muskrats and returned to control in rabbits. Hearts from muskrats and guinea pigs were removed under ether anesthesia and perfused retrograde with a physiological saline solution. Developed tension, heart rate, coronary blood flow, and lactate dehydrogenase (LDH) output were monitored. During 30 min of hypoxia, muskrat hearts developed a profound bradycardia compared to guinea pigs. Coronary flow increased in both species but less so in muskrats. Guinea pig hearts developed contracture whereas muskrat hearts relaxed. During reoxygenation heart rate and coronary blood flow returned toward normal but cells released large amounts of LDH, indicating cell damage. It is concluded that the isolated heart of the muskrat, a diving mammal, is better able to deal with hypoxia than the heart of the nondividing guinea pig and rabbit.

Animals↗