PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “ADAPTATION, PHYSIOLOGICAL”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed1995

Collateral arterial blood supply to the pregnant uterus in the sheep.

The common internal iliac artery in the sheep gives rise to the arteries which are the primary source of blood to the uterus. We have used a vascular occluder placed on the common internal iliac artery of the pregnant sheep to induce and study the effects of chronic fetal hypoxaemia. We have noted that uterine blood flow and fetal oxygenation improve within 5 d of occlusion of the common internal iliac artery. To investigate the basis of this observation we performed serial angiograms and postmortem examinations of the uterine arterial circulation in pregnant sheep under normal conditions and after 7 d of blood flow occlusion. We identified distal anastomoses on the surface of the uterus between the middle uterine and internal pudendal arteries by way of the urogenital arteries and their branches. Furthermore, the internal pudendal artery filled retrogradely through other branches when the vessel was ligated at its origin. The development of a collateral circulation to the uterus in response to chronic common internal iliac artery occlusion is a physiological adaptation to maintain an adequate supply of blood to the uterus and thus to maintain fetal oxygen delivery.

Adaptation, Physiological↗
PubMed1993

Some factors affecting birth weights in Morogoro, Tanzania.

Three hundred and thirty two pregnant women who were attending three antenatal clinics in Morogoro Municipality in Tanzania were followed in their third trimester of pregnancy in a study which aimed at finding if there was any association between weight gain in third trimester and birth weight of singleton deliveries. The relationship between weight and gestational period, age of the mother, parity and maternal weight near term were also studied. Univariate regression analysis showed that there was a strong positive correlation between birth weight and gestational period. Correlation was also found between birth weight and age of the mother, parity and weight near term, while a week correlation was found between birth weight and maternal weight gain in the third trimester. Multiple regression analysis showed that only the gestation period and weight near term were independently related to birth weight. Despite low maternal weight gain, birth weight was not affected, this shows that there might be some physiological adaptation which come into play to protect the foetus where a woman is subjected to inadequate nutrition during pregnancy.

Adaptation, Physiological↗
PubMed1994

The clinical use of upper extremity exercise.

There has been a revival of interest in the interaction between arm exercise and ventilation. Although arm ergometry continues to be the gold standard for the testing and training of upper extremities, an increasingly larger body of evidence indicates a more important role for the testing and training of upper extremities in forms that more closely resemble their physiologic adaptation in humans. As our knowledge of the functional anatomy of shoulder girdle muscles improves, so will our capacity to apply this knowledge in more rational, effective exercise regimens.

Adaptation, Physiological↗
PubMed1993

Functional studies of the human cerebellum with positron emission tomography.

New techniques of functional imaging with PET have resulted in improved understanding of the organisation of the human brain at systems level. Many studies have concentrated on the organisation of the cerebral cortex, while the cerebellum has been subjected to less intensive investigations. In the motor system the contralateral cerebellum is intimately related to the functions of the primary motor cortex. This has been demonstrated in a number of studies involving simple and more complex motor activations. The relationship has also been demonstrated in pathology. The role of the cerebellum in the generation of tremor has been the subject of some considerable study with the demonstration of functional relationships between the olivary nucleus and the cerebellum as well as between the cerebellum, thalamus and motor cortex in essential and parkinsonian tremor. The cerebellum is also involved in motor learning. Parts of the motor system exhibit physiological adaptation during the repeated performance of a simple motor task. The cerebellum, in particular, shows a decrease in regional blood flow with practice of a motor task despite a similar performance. A number of recent reports suggest that the cerebellum is also involved in cognitive functions and particularly language. Functional neuroimaging has not addressed this problem explicitly; however, studies of severely depressed patients with cognitive impairments have shown an unexpected but interesting result in that impaired cognition but not the state of mind is associated with increases in cerebellar activity. The reason for the paucity of systematic investigations of cerebellar function has been the limited field of view, sensitivity and resolution of PET cameras.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1994

Thermoregulation in neonates.

Thermoregulation is a critical physiologic function that is closely related to the transition and survival of the infant. An understanding of transitional events and the physiologic adaptations that neonates must make is essential to helping the nurse provide an appropriate environment and help infants maintain thermal stability. This article reviews neonatal thermal regulation, heat loss and gain, and the thermal response that is generated when thermal stability is threatened.

Adaptation, Physiological↗
PubMed1996

[Perioperative and postoperative normovolemic anemia. Physiological compensation, monitoring and risk evaluation].

We accept increasingly lower haemoglobin concentrations in order to avoid erythrocyte transfusions in surgical patients. Knowledge about the physiological adaptation to anaemia, and how this is affected by disease and anaesthesia, are necessary in order to foresee when compensation may be inadequate. Only a few methods are available at present for monitoring tissue oxygenation i.e. mixed venous oxygen saturation, systemic lactacidosis and ECG. In acute haemodilution, cardiac output increases by about 30%, mainly because of a drop in peripheral resistance. Increased contractility and heart rate may contribute to the hyperdynamic circulation and elevate myocardial oxygen demand. In acute anaemia the maximal oxygen extraction ratio in humans is approximately 0.5. Erythrocyte transfusion carries a small, but not negligible risk of infectious disease transmission and immunological incompatibility. Whether allogen transfusions increase the rate of postoperative infections and recurrence of cancer is still a debated issue. The low rate of complications associated with erythrocyte transfusions indicates that the margins of safety should not be too narrow, and that the transfusion trigger should be individualized between 5 and 10 g/100 ml.

Adaptation, Physiological↗
PubMed1996

Changes in the genetic expression of membrane proteins as a determinant of myocardial dysfunction.

In most of the cases, cardiac hypertrophy is the physiological adaptation of the heart to a disease, and the causal disease is usually arterial and cardiac failure indicates the limits of the mechanical adaptation. Such an adaptational process is aggravated by an additional factor, namely fibrosis which is not related to mechanical overload, but depends upon ischemia, senescence and hormones or peptides. Myocardial adaptation or dysadaptation is a species-specific process because the regulation of calcium movements, the main myocardial intracellular messenger differs from one animal species to the other. In this chapter, we will use, as a model, the rat, and finally will report what we know concerning the biology of the human failing heart.

Adaptation, Physiological↗
PubMed1998

Changing concepts. The effects of occlusion on periodontitis.

Despite volumes of publications on the theory of occlusion, occlusal design, and equilibration techniques, there have been few well-designed human studies directed at answering the question does occlusal trauma modify the progression of attachment loss in periodontitis. The articles reviewed indicate that occlusal forces can cause changes in the alveolar bone and periodontal connective tissue both in the presence and in the absence of periodontitis. These changes can affect tooth mobility and clinical probing depth. Although occlusal forces do not initiate periodontitis, results are inconclusive as to if or how these forces affect attachment loss owing to plaque-induced inflammatory periodontal disease. Although some studies reported a relationship between increased attachment loss and tooth mobility, others found no relationship between attachment loss and abnormal occlusal contacts. Tooth mobility results from a variety of factors, including alveolar bone loss, attachment loss, disruption of the periodontal tissues by inflammation, widening of the PDL in response to occlusal forces (physiologic adaptation), PDL atrophy from disuse, and other processes that effect the periodontium. Therefore, any relationship found between tooth mobility and progressing periodontitis does not necessarily implicate or defend occlusion as a cofactor in the progression of inflammatory periodontal disease. Periodontitis can be treated and periodontal health maintained without occlusal adjustment and in the presence of traumatic occlusal forces. Statistically greater gains in clinical periodontal attachment level have been reported, however, when occlusal adjustment was included as a component of periodontal therapy. The extent to which this is clinically meaningful is unclear. Once periodontal health is established, occlusal therapy can be used to reduce mobility, to regain bone lost owing to traumatic occlusal forces, and to treat a variety of clinical problems related to occlusal instability and restorative needs. The clinician's decision whether or not to use occlusal adjustment as a component of periodontal therapy should be related to an evaluation of clinical factors involving the patient's comfort and function and not based on the assumption that occlusal adjustment is necessary to stop the progression of periodontitis.

Adaptation, Physiological↗
PubMed1976

Medical experiment M-171: results from the second manned Skylab mission.

Preflight, inflight, and postflight exercise response tests were conducted on the astronauts of the second Skylab mission (Skylab 3) as part of an evaluation of physiological adaptation to long-term weightlessness. The flight phase of this mission was 59 d in duration. An exercise protocol was designed around a bicycle ergometer which was used to apply work loads approximating 25, 50, and 75% of each crewman's measured maximum aerobic capacity (VO2 max). Respiratory gas exchange (VO2, VCO2, and VE), heart rate, and blood pressure were measured during all tests; cardiac output was measured at selected times during preflight and postflight tests. Data obtained both at rest and during exercise in flight showed no consistent changes which would indicate a degraded physical work capacity. In fact, heart rate during exercise actually decreased for all crewmen in flight. This response indicated improved physical fitness in flight relative to preflight. The improved physical condition of this crew relative to that of the first Skylab crew is attributed to frequent performance of high levels of aerobic exercise in flight. The postflight period of readaptation of 1 G was characterized by a marked tachycardia, during which time stroke volume was decreased. This response returned to normal within 5 d postflight.

Adaptation, Physiological↗
PubMed1998

Diabetes mellitus and sports.

The adolescent with insulin-dependent diabetes mellitus (IDDM) can safely participate in sports activities without interference from the disease. To ensure safe and successful participation, clinicians must appreciate how diabetes may alter the physiologic adaptation to strenuous exercise and how an individualized self-care plan can empower the adolescent with IDDM to effectively manage meal planning, blood glucose testing, and insulin injections. Various types of insulin, insulin schedules, and insulin delivery devices that may suit a wide variety of training and activity regimens are described.

Adaptation, Physiological↗
PubMed2006

Twenty years of research on cytokine-induced sickness behavior.

Cytokine-induced sickness behavior was recognized within a few years of the cloning and expression of interferon-alpha, IL-1 and IL-2, which occurred around the time that the first issue of Brain, Behavior, and Immunity was published in 1987. Phase I clinical trials established that injection of recombinant cytokines into cancer patients led to a variety of psychological disturbances. It was subsequently shown that physiological concentrations of proinflammatory cytokines that occur after infection act in the brain to induce common symptoms of sickness, such as loss of appetite, sleepiness, withdrawal from normal social activities, fever, aching joints and fatigue. This syndrome was defined as sickness behavior and is now recognized to be part of a motivational system that reorganizes the organism's priorities to facilitate recovery from the infection. Cytokines convey to the brain that an infection has occurred in the periphery, and this action of cytokines can occur via the traditional endocrine route via the blood or by direct neural transmission via the afferent vagus nerve. The finding that sickness behavior occurs in all mammals and birds indicates that communication between the immune system and brain has been evolutionarily conserved and forms an important physiological adaptive response that favors survival of the organism during infections. The fact that cytokines act in the brain to induce physiological adaptations that promote survival has led to the hypothesis that inappropriate, prolonged activation of the innate immune system may be involved in a number of pathological disturbances in the brain, ranging from Alzheimer's disease to stroke. Conversely, the newly-defined role of cytokines in a wide variety of systemic co-morbid conditions, ranging from chronic heart failure to obesity, may begin to explain changes in the mental state of these subjects. Indeed, the newest findings of cytokine actions in the brain offer some of the first clues about the pathophysiology of certain mental health disorders, including depression. The time is ripe to begin to move these fundamental discoveries in mice to man and some of the pharmacological tools are already available to antagonize the detrimental actions of cytokines.

Adaptation, Physiological↗
PubMed1996

Cardiovascular and thermal responses to SCUBA diving.

Recreational SCUBA diving exposes individuals to environmental stresses not often encountered in other types of activity. These stresses include increased ambient pressure, raised partial pressure of O(2), increased resistance to movement, added weight and drag of diving equipment, cold stress, and a higher breathing resistance. One means to understand how such stresses affect a diver is to employ the stress-strain-adaptive response model. Physiologic adaptations, like an increase in VO(2) in response to cold stress, will minimize the strain placed on thermal balance. Nonphysiologic adaptive responses include those behavioral and equipment interventions that isolate the diver from a particular stress. Self-contained underwater breathing apparatus (SCUBA) isolates the diver from the inability to extract O(2) from the water; dive garments minimize the stress of cold water immersion. This review will focus on cardiorespiratory and thermal responses to SCUBA diving, using the stress-strain-adaptive response model to illustrate the interaction between diver and environment. Some responses like hyperventilation, cardiac arrhythmias, or cold injury due to vasoconstriction are not considered adaptive but are realistic possibilities in diving environments.

Adaptation, Physiological↗
PubMed1995

Applied physiology of triathlon.

The triathlon is a 3-event endurance sport in which athletes compete sequentially in swimming, cycling and running. The primary determinant of success is the ability to sustain a high rate of energy expenditure for prolonged periods of time. Exercise training-induced physiological adaptations in virtually all systems of the body allow the athlete to accomplish this. Aerobic capacity (measured as maximal oxygen uptake, VO2max), economy of motion (submaximal VO2) and fractional utilisation of maximal capacity (%VO2max) reflect the integrated responses of these physiological adaptations. Numerous studies have reported relatively high mean VO2max values for various groups of triathletes that are comparable to those reported for athletes in single-event endurance sports and clearly above those reported for untrained individuals. In shorter distance triathlons and in studies using recreational (rather than elite) triathletes, VO2max is related to performance in the corresponding event of the triathlon (e.g. tethered swimming VO2max with swim time). In longer events and with more elite triathletes, VO2max correlates less well with performance. The physiological adaptations that correspond to and facilitate improved VO2max occur centrally in the cardiovascular system, centred on increased maximal cardiac output, and peripherally in the metabolic systems, centred around increased arterio-venous O2 (a-v O2) difference. While a high VO2max in individuals is clearly of importance to triathlon performance, energy output must be sustained for long periods of time, making economy of motion also very important. Studies suggests that competitive swimmers have better swimming economy than triathletes. However, since many triathletes have previously been competitive swimmers this finding is questionable. The finding suggests that triathletes from nonswimming backgrounds would benefit from improving swimming technique rather than concentrating training workouts solely on distance. In cycling and running, comparison studies have not been done. Economy of motion in swimming, cycling and running have all been found to be correlated with comparable event performance. Training to improve swimming economy can be done without prior exercise, but training to improve swimming economy can be done without prior exercise, but training to improve cycling and running economy should take the multimode nature of a triathlon into consideration. That is, swimming should precede cycling economy training, and cycling should precede running economy training. Cardiovascular, metabolic and neuromuscular adaptations are the main physiological correlates of improved movement economy. Since exercise-induced stress on most physiological systems is based on relative, rather than absolute, exercise intensity, training and racing intensities are frequently quantified as a percentage of maximal capacity of %VO2max.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗