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PubMedDate not supplied

Evolution and consequences of endothermy in fishes.

Regional endothermy, the conservation of metabolic heat by vascular countercurrent heat exchangers to elevate the temperature of the slow-twitch locomotor muscle, eyes and brain, or viscera, has evolved independently among several fish lineages, including lamnid sharks, billfishes, and tunas. All are large, active, pelagic species with high energy demands that undertake long-distance migrations and move vertically within the water column, thereby encountering a range of water temperatures. After summarizing the occurrence of endothermy among fishes, the evidence for two hypothesized advantages of endothermy in fishes, thermal niche expansion and enhancement of aerobic swimming performance, is analyzed using phylogenetic comparisons between endothermic fishes and their ectothermic relatives. Thermal niche expansion is supported by mapping endothermic characters onto phylogenies and by combining information about the thermal niche of extant species, the fossil record, and paleoceanographic conditions during the time that endothermic fishes radiated. However, it is difficult to show that endothermy was required for niche expansion, and adaptations other than endothermy are necessary for repeated diving below the thermocline. Although the convergent evolution of the ability to elevate slow-twitch, oxidative locomotor muscle temperatures suggests a selective advantage for that trait, comparisons of tunas and their ectothermic sister species (mackerels and bonitos) provide no direct support of the hypothesis that endothermy results in increased aerobic swimming speeds, slow-oxidative muscle power, or energetic efficiency. Endothermy is associated with higher standard metabolic rates, which may result from high aerobic capacities required by these high-performance fishes to conduct many aerobic activities simultaneously. A high standard metabolic rate indicates that the benefits of endothermy may be offset by significant energetic costs.

Adaptation, Physiological↗

PubMed2002

Prognosis of hematologic malignancies does not predict intensive care unit mortality.

OBJECTIVE: To evaluate the correlation between specific prognosis of hematologic malignancies on the one hand and intensive care unit and hospital mortality in critically ill patients with hematologic malignancies on the other hand. DESIGN: Observational study during a 10-yr period. SETTING: A 22-bed medical-surgical intensive care unit. PATIENTS: A total of 84 consecutive patients with nonterminal hematologic malignancies with medical complications requiring intensive care. INTERVENTIONS: None. MEASUREMENTS: Demographic factors, acute physiology and organ dysfunction scores, microbiology, therapeutic support, and hematologic factors data on admission and during the intensive care unit stay were collected, together with mortality follow-up. Based on specific-disease prognostic factors and related published survival curves, the prognosis of hematologic malignancies was assessed and defined as good, intermediate, or poor according to a 3-yr survival probability of >50%, 20-50%, or <20%, respectively. MAIN RESULTS: Prognosis of hematologic malignancies does not predict intensive care unit or hospital mortality and almost reaches significance for 6-mo mortality (53%, 71%, and 84% rate for patients with good, intermediate, and poor prognosis, respectively, p =.058), but it determines long-term survival (p =.008). Intensive care unit, hospital, and 6-mo overall mortality rates were 38%, 61%, and 75%, respectively. Using multivariate analysis, intensive care unit mortality was best predicted on admission by respiratory failure and fungal infection, whereas hospital mortality was predicted by the number of organ failures, the bone marrow transplant status, and the presence of fungal infection. The Acute Physiology and Chronic Health Evaluation II and the Simplified Acute Physiology Score II had no prognostic value, whereas the difference of the Multiple Organ Dysfunction Score between at the time of admission and at day 5 allowed quick prediction of hospital mortality. Diseases with the poorest 6-mo prognosis were acute myeloid leukemia and non-Hodgkin lymphoma. CONCLUSION The severity of the underlying hematologic malignancies does not influence intensive care unit or hospital mortality. Short-term prognosis is exclusively predicted by acute organ dysfunctions and by a pathogen's aggressiveness. Therefore, reluctance to admit patients with nonterminal hematologic malignancies to the intensive care unit based only on the prognosis of their underlying hematologic malignancy does not seem justified.

APACHE↗

PubMedDate not supplied

[Method of studying acceleration tolerance of pilots in flight conditions].

The following procedure was used to study the pilot's tolerance to acceleration inflight. Experiments were carried out in a specially equipped plane with a dual monitoring system. Inflight the pilot performed 3 dives, attaining 3.0, 5.0 and 6.0 g for 30 sec at an interval of 1-2 min and an onset rate of 0.4-0.6 g/sec. The control over the health state and performance of the pilot was maintained by the coach as well as with the aid of breathing rate, ECG, ear pulse rate recordings and cynematography of the pilot's face during exposure to acceleration. These methods were employed in experimental flights of a good number of pilots. The results show that the methods may well be used to better medical monitoring inflight and to identify subjects with decreased tolerance to acceleration.

Acceleration↗

PubMed1997

[Principle requirements of an electromechanical transducer for implantable hearing aids in inner hearing hearing loss. II: Clinical aspects].

In cases of sensorineural hearing loss, an electromechanical transducer of implantable hearing aids should partially or completely compensate for the cochlea amplifier (CA) failure that occurs in most of these patients. CA failure can be clinically identified by a positive recruitment and amplitude loss in otoacoustic emissions (OAE). In a healthy ear, the basis of the CA is the motility of the outer hair cells. A transducer that replaces functions of the CA can be termed CAI (cochlea amplifier implant). A CAI should fulfill five requirements: (1) production of a vibratory output signal, (2) reinforcement of the travelling wave in the inner ear, (3) imitation of the physiological, nonlinear behavior of the CA, (4) reinforcement without distortion, and (5) steady amplitude at rising frequencies. Compensation of frequency selectivity of the CA would also be desirable; however, this can hardly be expected from an implant. If the requirements are fulfilled, one can expect superior sound and hearing quality compared to a conventional hearing aid. Frequency should range from 50 to 10,000 Hz and have an increasing transfer function beyond 1000 Hz. Equivalent levels in the high frequency range should clearly exceed 100 dB SPL. Total distortion should at best amount to 1%. The CAI should function as a totally implantable hearing aid requiring minimum energy. The outer ear canal has to remain open so that occlusion cannot occur; the ossicular chain should be kept intact or repairable, and the implantation technique should allow explantation. The quality of the implant should make possible a CE approval in Europe and an FDA approval in the USA. Furthermore, there should be no risks involved if computer tomography, MRI, or PET examination are undertaken. Underwater diving to a depth of 2-3 m should also be permissible. Minimization of risks that occur near strong magnetic fields or high frequency fields is of great practical importance.

Cochlear Implants↗

PubMed1994

Effect of mechanical shock on hydrostatic balance and survival of mosquito pupae.

The presence and distribution of ventral air space gas assures that mosquito pupae are positively buoyant and that they float, dive, and ascend in an upright, balanced orientation. Our objective was to test the effects of mechanical shocks of varying magnitude on mosquito pupae representing 3 genera. Forces that disrupt the pupa's buoyancy and/or hydrostatic balance are of a much lower magnitude than those that would cause tissue damage. Once hydrostatic balance and/or buoyancy are compromised, pupae are unable to restore them and eventually drown. This could represent a weak link in the mosquito life cycle. It is possible that mechanical shock or sound-generating devices could be designed that could break this link.

Aedes↗

PubMed2000

Lipid composition of erythrocytes and thrombocytes of a subantarctic seabird, the king penguin.

Phospholipid (PL) compositions and fatty acid (FA) patterns of PL were determined in the erythrocytes and blood thrombocytes of a seabird, the king penguin, living in the subantarctic area and feeding on prey rich in n-3 polyunsaturated FA. Results were compared between birds in three different physiological states (breeding and molting adults, chicks) to those reported for other birds. In erythrocytes, the ratios of cholesterol to PL and of sphingomyelin to phosphatidylcholine (PC) were lower than in other birds. The PL distribution was similar to those previously reported in the hen and pigeon. In contrast to other birds, cardiolipin levels were unexpectedly high (4%). Very long chain n-3 FA were abundant (13-27%) in phosphatidylethanolamine (PE), phosphatidylserine and PC, probably in relation to the natural diet of these birds. Among n-3 FA, 22:6n-3 was the most abundant in all PL (2-20%), whereas the highest levels of arachidonic acid were observed in PE (14%). In thrombocytes, the PL distribution and FA composition of the main PL (PC, PE) differed from those of erythrocytes, and in particular, levels of n-3 FA (9-12%) were 1.5-2 times lower. The highest levels of arachidonic acid were found in phosphatidylinositol (24%). The lipid profile of penguin erythrocytes could contribute to the efficiency of blood circulation and oxygen delivery in microvascular beds, thus favoring diving capacity of these animals. Our observations do not support the hypothesis of a common origin of avian thrombocytes and erythrocytes.

Animals↗

PubMed2001

Discovery and description of giant submarine smectite cones on the seafloor in Eyjafjordur, northern Iceland, and a novel thermal microbial habitat.

With the submersible JAGO and by scuba diving we discovered three remarkable geothermal cones, rising 33, 25, and 45 m from the seafloor at a depth of 65 m in Eyjafjordur, northern Iceland. The greatest geothermal activity was on the highest cone, which discharged up to 50 liters of freshwater per s at 72 degrees C and pH 10.0. The cones were built up from precipitated smectite, formed by mixing of the hot SiO2-rich geothermal fluid with the cold Mg-rich seawater. By connecting a rubber hose to one outflow, about 240 liters of pure geothermal fluids was concentrated through a 0.2-microm-pore-size filter. Among 50 thermophilic isolates, we found members of Bacillus and Thermonema and a new unidentified low-G+C gram-positive member of the Bacteria as well as one member of the Archaea, Desulfurococcus mobilis. Analysis of small-subunit rRNA genes PCR amplified and cloned directly from environmental DNA showed that 41 out of 45 Bacteria sequences belonged to members of the Aquificales, whereas all of the 10 Archaea sequences belonged to the Korarchaeota. The physiological characteristics of isolates from different parts of the cones indicate a completely freshwater habitat, supporting the possibility of subterranean transmittance of terrestrial organisms.

Aluminum Silicates↗

PubMed1988

[Normalization of the adaptive avoidance reaction in rats using substances with nootropic activity].

The system of double coaxial cylinders filled with water was used as a device for studying simple extrapolation behaviour of rats. The amount of rats which were able to dive under the lower edge of the inner cylinder, without reaching the bottom of the outer cylinder and the latency of this avoidance reaction were considered as a measure of extrapolation ability. This reaction was altered by the pretreatment of animals with cycloheximide, a protein synthesis inhibitor. Piracetam as a standard nootropic, sodium and lithium hydroxybutyrate as substances with a potential nootropic effect were shown to be able to antagonize the damaging effect of cycloheximide on the avoidance performance. Benzodiazepine tranquilizer, phenazepam, in contrast to nootropics, evokes additional worsening of extrapolation reaction. Normalization of avoidance disturbed by cycloheximide, can be used as an adequate and informative approach for screening of nootropics.

Adaptation, Physiological↗

PubMed2005

The three-dimensional flight of red-footed boobies: adaptations to foraging in a tropical environment?

In seabirds a broad variety of morphologies, flight styles and feeding methods exist as an adaptation to optimal foraging in contrasted marine environments for a wide variety of prey types. Because of the low productivity of tropical waters it is expected that specific flight and foraging techniques have been selected there, but very few data are available. By using five different types of high-precision miniaturized logger (global positioning systems, accelerometers, time depth recorders, activity recorders, altimeters) we studied the way a seabird is foraging over tropical waters. Red-footed boobies are foraging in the day, never foraging at night, probably as a result of predation risks. They make extensive use of wind conditions, flying preferentially with crosswinds at median speed of 38 km h(-1), reaching highest speeds with tail winds. They spent 66% of the foraging trip in flight, using a flap-glide flight, and gliding 68% of the flight. Travelling at low costs was regularly interrupted by extremely active foraging periods where birds are very frequently touching water for landing, plunge diving or surface diving (30 landings h(-1)). Dives were shallow (maximum 2.4 m) but frequent (4.5 dives h(-1)), most being plunge dives. While chasing for very mobile prey like flying fishes, boobies have adopted a very active and specific hunting behaviour, but the use of wind allows them to reduce travelling cost by their extensive use of gliding. During the foraging and travelling phases birds climb regularly to altitudes of 20-50 m to spot prey or congeners. During the final phase of the flight, they climb to high altitudes, up to 500 m, probably to avoid attacks by frigatebirds along the coasts. This study demonstrates the use by boobies of a series of very specific flight and activity patterns that have probably been selected as adaptations to the conditions of tropical waters.

Adaptation, Physiological↗

PubMed1997

Cultured epithelial autografts: diving from surgery into matrix biology.

Cultured epithelial autografts offer an exciting approach to cover extensive skin wounds. The main problem of this method is mechanical instability during the first weeks after grafting. There is evidence that the shortcomings of autografting cultured keratinocytes result from the lack of a mature and functional dermo-epidermal junction. This article summarizes the current knowledge regarding the de novo formation of the dermo-epidermal junction and the dynamics of "take" and stabilization of cultured epithelial autografts. Future strategies are discussed of how to improve and accelerate the process conferring definitive stabilization of cultured epithelial autografts including the potential therapeutic use of transglutaminase as well as cocultivation of a dermo-epidermal equivalent in order to facilitate a permanent skin replacement.

Burns↗

PubMed2001

Invited review: Adaptive responses of skeletal muscle to intermittent hypoxia: the known and the unknown.

Intermittent hypoxia (IH) describes conditions of repeated, transient reductions in O2 that may trigger unique adaptations. Rest periods during IH may avoid potentially detrimental effects of long-term O2 deprivation. For skeletal muscle, IH can occur in conditions of obstructive sleep apnea, transient altitude exposures (with or without exercise), intermittent claudication, cardiopulmonary resuscitation, neonatal blood flow obstruction, and diving responses of marine animals. Although it is likely that adaptations in these conditions vary, some patterns emerge. Low levels of hypoxia shift metabolic enzyme activity toward greater aerobic poise; extreme hypoxia shifts metabolism toward greater anaerobic potential. Some conditions of IH may also inhibit lactate release during exercise. Many related cellular phenomena could be involved in the response, including activation of specific O2 sensors, reactive oxygen and nitrogen species, preconditioning, hypoxia-induced transcription factors, regulation of ion channels, and influences of paracrine/hormonal stimuli. The net effect of a variety of adaptive programs to IH may be to preserve contractile function and cell integrity in hypoxia or anoxia, a response that does not always translate into improvements in exercise performance.

Adaptation, Physiological↗

PubMed1984

Cerebral arterial air embolism: I. Is there benefit in beginning HBO treatment at 6 bar?

A method for studying treatment of cerebral arterial gas embolism in dogs is described. The model produces severe cortical dysfunction and cerebral blood flow deficits. The efficacy of treatment was assessed using median nerve somatosensory cortical evoked potentials (CEP), [14C]iodoantipyrene autoradiographic cerebral blood flow studies, brain water content, and various physiological parameters. A direct comparison of modified U.S. Navy Treatment Tables 6 and 6A is reported. Complete recovery of CEP was not seen after 90 min of treatment. The maximum rate of CEP recovery occurred in the first 15 min of treatment. Recovery continued out to 60 min. Thereafter, some dogs on treatment 6A showed signs of deterioration. The cerebral blood flow studies were the same in both groups and showed no sign of pathologically low levels of flow. It appeared that there was no advantage in preceding 2.8-bar (60-ft) oxygen treatments with compression to 6 bar (165 ft) on air for the treatment of arterial air embolism in this model.

Animals↗

PubMed2001

RXP 407, a selective inhibitor of the N-domain of angiotensin I-converting enzyme, blocks in vivo the degradation of hemoregulatory peptide acetyl-Ser-Asp-Lys-Pro with no effect on angiotensin I hydrolysis.

The phosphinic peptide RXP 407 has recently been identified as the first potent selective inhibitor of the N-active site (domain) of angiotensin-converting enzyme (ACE) in vitro. The aim of this study was to probe the in vivo efficacy of this new ACE inhibitor and to assess its effect on the metabolism of AcSDKP and angiotensin I. In mice infused with increasing doses of RXP 407 (0.1--30 mg/kg/30 min), plasma concentrations of AcSDKP, a physiological substrate of the N-domain, increased significantly and dose dependently toward a plateau 4 to 6 times the basal levels. RXP 407 significantly and dose dependently inhibited ex vivo plasma ACE N-domain activity, whereas it had no inhibitory activity toward the ACE C-domain. RXP 407 (10 mg/kg) did not inhibit the pressor response to an i.v. angiotensin I bolus injection in mice. In contrast, lisinopril infusion (5 and 10 mg/kg/30 min) affected the metabolism of both AcSDKP and angiotensin I. Thus, RXP 407 is the first ACE inhibitor that might be used to control selectively AcSDKP metabolism with no effect on blood pressure regulation.

Angiotensin I↗

PubMed2006

Vascular distribution of an ultrasound contrast agent used to simulate decompression bubbles.

OBJECTIVE: The objectives of this preliminary work were to evaluate the distribution of an ultrasound contrast agent (UCA) (microbubbles) in different arterial regions (brain, kidney, lower limbs) using the Doppler spectrum brightness analysis and to discuss the results in the context of decompression physiology. METHOD: There were four patients who instrumented with two pulsed Doppler sensors in order to monitor in real-time the spectrum of the middle cerebral femoral arteries. Renal arteries were investigated using an echo-Doppler probe handled by a sonographer. Measurements of the systolic mean, diastolic frequencies, qualitative, and quantitative analysis of the spectrum brightness intensity were performed before and after intravenous injection of a UCA. RESULTS: All of the systolic mean and diastolic arterial frequencies remained constant during the experiment. Some seconds after the first injection, the cerebral spectrum was heterogeneously enhanced with strong flashes over the entire spectrum. The renal and femoral spectrums were homogeneously reinforced. The spectrum brightness patterns did not change during the first 10 min. DISCUSSION: This work shows that the distribution of the UCA microbubbles within the vessel sections changed according to the distance from the heart, as suggested by the spectrum recorded at different sites. By mixing the blood, the heart could re-aggregate the UCA particles, even when they returned from the distal vascular regions where they were homogeneously distributed. The circulating microbubbles and their distribution within the arteries should be considered in decompression procedures with repetitive dives.

Adult↗

PubMed1989

Numerical simulation of systemic O2 and CO2 exchange in a hyperbaric environment.

The process of gas exchange in systemic capillaries and its surrounding tissue is simulated numerically in a hyperbaric environment, taking into account the molecular diffusion, convection, saturation of haemoglobin with O2 and CO2, and the metabolic activity in the tissue. Krogh tissue-cylinder is used as a geometrical representation of the capillary-tissue system. The resulting system of non-linear governing equations together with the physiologically relevant boundary conditions is solved numerically. It is found that the concentration of oxygen decreases from the axis of the capillary to the tissue periphery whereas the concentration of carbon dioxide increases. It is shown that very little CO2 is transported radially. The location of the vulnerable region from the point of view of CO2 accumulation is found to be the rim (r = R2, z = L) situated at the periphery of the tissue near the venous end of the capillary. It is also found that accumulation of O2 decreases whereas that of CO2 increases in a hyperbaric environment. Finally, it is surmised that one of the reasons in causing discomfort among divers could be excessive accumulation of CO2 in the tissue.

Biological Transport↗

PubMed1995

Implantable data logging system for heart rate and body temperature: its application to the estimation of field metabolic rates in Antarctic predators.

The metabolic rate of free-ranging animals is difficult to measure, but of great importance in understanding the interactions of a species with its environment. Heart rate can, if correctly validated and calibrated, give an estimate of metabolic rate, with both a fine time resolution and over long periods. The telemetry of heart rate is well documented, but is not appropriate over long ranges (possibly several thousands of kilometres) or for diving species. An implantable data logger has therefore been developed for the long term recording of heart rate and body temperature. The logger is built using hybrid and ASIC construction techniques, weighs 20 g and measures 55 x 24 x 6 mm. The device is programmable, and its solid-state memory holds over 70 days of data if, for example, heart rate is counted and stored every minute. Current consumption is 155 microA while logging, 50 microA during a programmable initial delay period, and less than 1 microA when the logger closes down after filling its memory. These loggers have been deployed for two field seasons in gentoo penguins, black-browed albatross and fur seals.

Animals↗

PubMedDate not supplied

The use of data loggers to determine the energetics and physiology of aquatic birds and mammals.

By deploying a data logger specifically designed for the purpose, it was possible to record heart rate, fH (beats/min), from free-ranging gentoo penguins, Pygoscelis papua, and Antarctic fur seals, Arctocephalus gazella, at the British Antarctic Survey Base at Bird Island. The heart rate data were then converted into oxygen consumption (VO2, mlO2 min-1 kg-1) and/or energy expenditure (W/kg) using equations that had been derived from calibration experiments. In these experiments the relationships between fH and VO2 were determined in animals at rest and while exercising at different levels on a treadmill or in a static water channel (penguins) and in a variable speed flume (California sea lions, Zalophus californianus, as surrogate fur seals) or in a static water channel (fur seals). The validity of using these relationships was tested by recording simultaneously fH, VO2 by direct respirometry and VCO2 by the doubly labelled water (DLW) technique in six penguins and in six California sea lions during 72 h and 24 h, respectively, at various levels of activity. For the penguins, both indirect methods gave mean algebraic errors within 2% of the measured VO2, whereas for the sea lions, the mean algebraic errors were 36.4% for the DLW method and 2.7% for the fH method. The range of errors was greater for the DLW method, in both species. Field data from 15 penguins indicate that the fH method provides data that are comparable to those obtained using the DLW method, but with the added advantage that they can be broken down into the energy costs for specific types of behaviour. The implanted data loggers also recorded the temperature of the abdominal cavity (T(ab)) and it was evident that this routinely decreased by approximately 2 degrees C during diving bouts and by a maximum of almost 5 degrees C. Such temperature decreases, particularly if representative of similar decreases in other tissues, may at least partly explain why the energy costs of travelling to and from the foraging site and of foraging itself are similar to those for penguins resting in water at 5 degrees C. Field data from 15 female fur seals indicate that, when the animals are ashore, there is good agreement between the values for mean energy expenditure obtained by the fH and DLW methods. However, when the animals are at sea, the values obtained by DLW are substantially greater than those obtained by fH. When the at-sea values are corrected for the apparent overestimations referred to above, there is good agreement between the data obtained using the two methods. The data derived from fH indicate that, as with the penguins, the energy expenditures during travelling to and from the foraging site and during foraging are similar to those of fur seals resting in water at 7 degrees C.

Animals↗

PubMed1985

Autonomic cardiovascular responses in old age.

The effect of age on autonomically mediated cardiovascular responses to certain manoeuvres was studied in 15, healthy, old men and women (60-80 years). The results were compared with groups of healthy young (about 25 years) and middle-aged (about 45 years) subjects. There was no significant reduction in cardiovascular responses between the young and middle-aged groups. Respiratory sinus arrhythmia, and heart rate, blood-pressure and contralateral forearm blood flow increases to isometric hand grip, as well as the heart rate decrease during a dive reflex test, were significantly attenuated in the old age group. The Valsalva ratio, and the heart rate and blood-pressure changes during an 8 min orthostatic test did not differ between the old and the two younger age groups. There seems to be only a moderate attenuation of autonomic cardiovascular responses to about 60 years, after which there is a more rapid decline. The difference in reduction between different responses, even those mediated by the same type of autonomic nerve, suggests that the decreased responses are not due to an isolated impaired function of the peripheral autonomic nerve. The impairment may be due to the receptor organ or a combination of defects in function of several parts of the autonomic nervous system in old age.

Adult↗