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At least 937 records · Page 52Linked to original sources
PubMed1987

Severe pregnancy-induced hypertension: postpartum care of the critically ill patient.

SPIH is a disease of unknown cause that contributes to maternal and neonatal morbidity and mortality rates. Familiarity with the normal physiologic adaptations of pregnancy and the confounding pathologic changes of SPIH will enable the health care professional to better understand the principles of management. Immediate therapeutic interventions are necessary to reverse hypertension and to prevent the life-threatening sequelae that may arise from this condition. Postpartum management is directed toward decreasing vasospasm and central nervous system irritability and maintaining fluid and electrolyte balance. Attention must be given to the special obstetric needs of these patients.

Acute Disease↗
PubMed1997

[Skiing over Greenland--physical and psychological changes].

Three Norwegian physicians crossed the inland glacier of Greenland on skis without any support. Body weight, fat and lean body mass was measured by dual X-ray absorptiometry scanning. Maximal oxygen uptake, lung capacity measurements, and various blood tests were recorded. Subjective health-related well-being and four transistory arousal states were also recorded (GHQ-30 and AD ACL, short form). One participant lost 1 kilo body weight, while the others gained 1 and 4 kilos, respectively, during the trip. Overall, lean body mass increased (1.2-4.0 kg), while body fat was reduced (0.4-2.7 kg). These changes reversed after four weeks. Bone mass, lung function and blood tests did not vary throughout the study period. The level of energy and calmness were high at baseline and even higher towards the end of the expedition, while the scores were low and stable for tiredness and tension. Subjective well-being increased for all participants towards the second half of the trip. We conclude that expeditions involving physical and mental strain can produce positive psychological changes. Catabolic conditions are avoidable. Changes in body mass composition revert quickly.

Adaptation, Physiological↗
PubMed1997

Cardiorespiratory response to exercise in elite Sherpa climbers transferred to sea level.

Himalayan Sherpas are well known for their extraordinary adaptation to high altitude and some of them for their outstanding physical performance during ascents to the highest summits. To cast light on this subject, we evaluated the cardiorespiratory response during exercise at sea level of six of the most acknowledged Sherpa climbers, mean age (+/- SD) 37 (+/- 7) yr old. Continuous electrocardiogram and breath-by-breath pulmonary gas exchange until exhaustion were obtained by following the Bruce protocol. We detected a maximal oxygen uptake (VO2max) of 66.7 (+/- 3.7) mL-min-1.kg-1, maximal cardiac frequency of 199 (+/- 7) beats.min-1, and ventilatory anaerobic threshold at 62 (+/- 4) % of VO2max. These factors could help to explain the greater performance level shown by several elite climbers of this ethnic group. The high functional reserve demonstrated by this very select group of highlanders could be associated with natural selection and with special physiological adaptations probably induced by long-training in a hostile environment.

Adult↗
PubMed2006

An evolutionary model for identifying genetic adaptation to high altitude.

Coordinated maternal/fetal responses to pregnancy are required to ensure continuous O2 delivery to the developing organism. Mammals employ distinctive reproductive strategies that afford their young an improved chance of survival through the completion or the reproductive period. Thus, mortality prior to the end of the reproductive period is concentrated in the earliest phases of the lifecycle. At high altitude, fetal growth restriction reduces birth weight and likely compromises survival during the early postnatal period. Population variation in the frequency of the altitude-associated increase in intrauterine growth restriction (IUGR) demonstrates that multigenerational Tibetan and Andean high-altitude populations are protected compared with shorter duration, European or Han (Chinese) residents. This experiment of nature permits testing the hypothesis that genetic factors (a) influence susceptibility to altitude-associated IUGR, (b) act on maternal vascular adjustments to pregnancy determining uteroplacental blood flow, and (c) involve genes which regulate and/or are regulated by hypoxia-inducible factors (HIFs). Serial, studies during pregnancy as well as postpartum in Andean and European residents of high (3600 m) and low (300 m) altitude will permit evaluation of whether uteroplacental O2 delivery is lower in the European than Andean women and, if so, the physiological factors responsible. Comparisons of HIF-targeted vasoactive substances and SNPs in or near HIF-regulatory or targeted genes will permit determination of whether these regions are distinctive in the Andean population. Studies coupling genetic and genomic approaches with more traditional physiological measures may be productively employed for determining the genetic mechanisms influencing physiological adaptation to high altitude.

Adolescent↗
PubMed1989

Evidence for the progressive and adaptive nature of spontaneous transformation in the NIH 3T3 cell line.

The NIH 3T3 mouse cell line is widely used as a recipient of DNA from tumors to demonstrate the presence of transforming oncogenes. We show that these cells produce transformed foci spontaneously if kept in the confluent state for more than 10 days. The formation of foci depends on the type and concentration of bovine serum used in the medium and passage history of the cells. Cells maintained in continuous exponential multiplication in the subconfluent state by transfer every 2-3 days in medium with 10% calf serum failed to develop the capacity to produce foci in 2% calf serum, but those transferred the same way in 2% calf serum or in 10% fetal bovine serum, which is a less potent growth stimulant, did develop that capacity to an increasing degree over time. The number of transformed cells increased sharply with the time that a culture remained in the confluent state. There are several morphological types and degrees of transformation, which indicates that the underlying changes are varied and the process is progressive. The results also suggest that transformation occurs in a fraction of an entire cell population that is undergoing a physiological adaptation to moderate constraints on its growth.

Animals↗
PubMed2005

[Successful coping and experience-dependent brain plasticity].

Recent progress in brain research has shown that the human brain, i.e., the neuronal and synaptic connectivity especially in higher cortical association centres, is much more plastic and use-dependent than previously thought. This contribution summarizes the present knowledge about this phenomenon of experience-dependent plasticity. Irritation, anxiety and the activation of the neuroendocrine stress-response-system is the most important trigger for the adaptive modification and reorganization of neuronal networks and synaptic connectivity. The experience and successful mastery of a large spectrum of different challenges already during early childhood and during later life diminish the risk of the acquisition and facilitation of maladaptive coping-strategies. Once established, the strongly facilitated neuronal networks involved in the generation of maladaptive behavioural patterns are difficult to reorganize. The experience of loss of control and the long-lasting activation of an uncontrollable stress response may contribute to the destabilization of the neuronal connectivity established in the course of acquisition of such maladaptive coping strategies.

Adaptation, Physiological↗
PubMed2005

Structure, function and molecular adaptations of haemoglobins of the polar cartilaginous fish Bathyraja eatonii and Raja hyperborea.

Cartilaginous fish are very ancient organisms. In the Antarctic sea, the modern chondrichthyan genera are poorly represented, with only three species of sharks and eight species of skates; the paucity of chondrichthyans is probably an ecological consequence of unusual trophic or habitat conditions in the Southern Ocean. In the Arctic, there are 26 species belonging to the class Chondrichthyes. Fish in the two polar regions have been subjected to different regional histories that have influenced the development of diversity: Antarctic marine organisms are highly stenothermal, in response to stable water temperatures, whereas the Arctic communities are exposed to seasonal temperature variations. The structure and function of the oxygen-transport haem protein from the Antarctic skate Bathyraja eatonii and from the Arctic skate Raja hyperborea (both of the subclass Elasmobranchii, order Rajiformes, family Rajidae) is reported in the present paper. These species have a single major haemoglobin (Hb 1; over 80% of the total). The Bohr-proton and the organophosphate-binding sites are absent. Thus the haemoglobins of northern and southern polar skates appear functionally similar, whereas differences were observed with several temperate elasmobranchs. Such evidence suggests that, in temperate and polar habitats, physiological adaptations have evolved along distinct pathways, whereas, in this case, the effect of the differences characterizing the two polar environments is negligible.

Amino Acid Sequence↗
PubMed2003

Pharmacokinetics of ivermectin in the yak (Bos grunniens).

The yak (Bos grunniens) belongs to the cattle family Bovidae and lives in the mountains of China and adjacent areas. Due to the physiological adaptations of yak to its environment and the lack of data, the ivermectin pharmacokinetic was studied following a single subcutaneous dose at the recommended dose for cattle (0.2 mg kg(-1)). The observed peak plasma concentration (Cmax) was 48.93 ng ml(-1) and the time to reach Cmax (Tmax) was 0.73 day. These results show a faster rate of absorption than in cattle. The values for the absorption half-life (t(1/2a)), the distribution half-life (t(1/2alpha)) and the terminal half-life (t(1/2beta)) were 0.31, 0.74 and 4.82 days, respectively. The calculated area under the concentration-time curve (AUC) was 146.2 ng day ml(-1) and the mean residence time (MRT) was 3.57 days. The availability of ivermectin appears low in yaks in comparison to cattle but equivalent to that reported in horses and is likely to be due to physiological characteristics of this species.

Absorption↗
PubMed2005

Hyperventilation in severe diabetic ketoacidosis.

OBJECTIVE: To explore whether the carbon dioxide-bicarbonate (P(CO(2))-HCO(3)) buffering system in blood and cerebrospinal fluid (CSF) in diabetic ketoacidosis should influence the approach to ventilation in patients at risk of cerebral edema. DATA SOURCE: Medline search, manual search of references in articles found in Medline search, and use of historical literature from 1933 to 1967. DESIGN: A clinical vignette is used--a child with severe diabetic ketoacidosis who presented with profound hypocapnia and then deteriorated--as a basis for discussion of integrative metabolic and vascular physiology. STUDY SELECTION: Studies included reports in diabetic ketoacidosis where arterial and CSF acid-base data have been presented. Studies where simultaneous acid-base, ventilation, respiratory quotient, and cerebral blood flow data are available. DATA EXTRACTION AND SYNTHESIS: We revisit a hypothesis and, by reassessing data, put forward an argument based on the significance of low [HCO(3)](CSF) and rising Pa(CO(2))- hyperventilation in diabetic ketoacidosis and the limit in biology of survival; repair of severe diabetic ketoacidosis and Pa(CO(2))-and mechanical ventilation. CONCLUSION: The review highlights a potential problem with mechanical ventilation in severe diabetic ketoacidosis and suggests that the P(CO(2))--HCO(3) hypothesis is consistent with data on cerebral edema in diabetic ketoacidosis. It also indicates that the recommendation to avoid induced hyperventilation early in the course of intensive care may be counter to the logic of adaptive physiology.

Acid-Base Equilibrium↗
PubMed2001

Effects of copper on olfaction of Colorado pikeminnow.

Effects of copper on olfaction of Colorado pikeminnow (Ptychocheilus lucius) were investigated by exposing fish for 24 or 96 h, then evaluating olfactory ability using a behavioral assay and observing olfactory structures using scanning electron microscopy (SEM). The behavioral assay measured a response known as fright reaction. Failure of exposed fish to demonstrate a fright reaction in the presence of skin homogenate assumed to contain fright pheromone was considered evidence of copper-induced loss of olfactory ability. Regression analysis was used to describe the response of fish as a function of copper concentration at each exposure duration. Olfactory ability declined with increasing copper concentration. For copper concentrations less than 66 microg/L, olfaction was more sensitive to exposure at 24 h than at 96 h. This result suggests that physiological adaptation and recovery of sensory ability occurred despite continuous exposure in the 96-h treatment. Protective mechanisms induced by exposure may have reduced sensitivity to copper by 96 h. Systematic surveys using SEM to detect presence or absence of olfactory receptors confirmed results of behavioral assays. Copper concentrations in one river inhabited by Colorado pikeminnow were compared with effective concentrations estimated by regression. Comparisons suggest that ambient copper concentrations may occasionally inhibit olfaction of wild fish.

Acclimatization↗
PubMed2006

The developmental origins of adult disease (Barker) hypothesis.

Many studies have provided evidence for the hypothesis that size at birth is related to the risk of developing disease in later life. In particular, links are well established between reduced birthweight and increased risk of coronary heart disease, diabetes, hypertension and stroke in adulthood. These relationships are modified by patterns of postnatal growth. The most widely accepted mechanisms thought to underlie these relationships are those of fetal programming by nutritional stimuli or excess fetal glucocorticoid exposure. It is suggested that the fetus makes physiological adaptations in response to changes in its environment to prepare itself for postnatal life. These changes may include epigenetic modification of gene expression. Less clear at this time are the relevance of fetal programming phenomena to twins and preterm babies, and whether any of these effects can be reversed after birth. Much current active research in this field will be of direct relevance to future obstetric practice.

Adult↗
PubMed1997

The neuroplastic phenomenon: a physiologic link between chronic pain and learning.

Recent advances in the understanding of how the mind works is the result of painstaking research which has isolated tiny regions of the spinal cord and brain, and singular chemical pathways or responses to sole neurotransmitters. The true nature of the central nervous system has eluded investigators because of its fully integrated, constantly changing structure and a symphony of chemical mediators. Each sensation, thought, feeling, movement and social interaction changes the structure and function of the brain. The mere presence of another living organism can have profound effects on the mind and body through imperceptible olfactory stimuli. Neuroplasticity is a general term referring to the ability of neurons to alter their structure and function in response to internal and external stimuli. Although differences occur with aging, this is a lifelong process. Physical and chemical neuroplastic changes occur with learning, memory and chronic pain. Evidence presented supports the notion that chronic pain is a maladaptive learned phenomenon. Further evidence supports that if severe pain is allowed to persist for more than 24 hours, the neuroplastic changes associated with the development of incurable chronic pain syndromes begin to take place. Even after chronic pain is well established, new thought and behavior patterns can be learned, allowing sufferers to restore more adaptive physiologic, cognitive and behavioral patterns.

Brain↗
PubMed1993

Arm and leg cycle cross-training effect on anaerobic threshold and heart rate in patients with coronary heart disease.

It has been suggested that the anaerobic threshold (AT) represents a minimal intensity for eliciting an exercise training adaptation. Thirteen men (age = 66 +/- 9; weight = 81 +/- 13kg) and two women (age = 58 +/- 21; weight = 70 +/- 3kg) with coronary heart disease (CHD) trained for 12 weeks to determine the effect of an exercise regimen composed of three- to six-minute intervals of alternating arm and leg cycling (cross-training) on AT. The patients cross-trained for a total of 30 minutes per session, three days per week. Maximal cycle ergometer tests with breath by breath ventilatory gas analyses were performed before and after training. Peak oxygen uptake increased by 8.9% and peak power output increased (p < .05) by 28.3%, whereas resting heart rate (HR) decreased (p < .05) by 9.6% as a result of the cross-training regimen. Cross-training did not effect a significant change in AT but HR at AT was decreased by 6.3% (p < .05). Arm and leg cross-training produced a physiological adaptation and may have reduced the HR threshold for effective exercise training.

Aged↗
PubMed2000

Stretch-dependent modulation of contractility and growth in smooth muscle of rat portal vein.

Increased intraluminal pressure of the rat portal vein in vivo causes hypertrophy and altered contractility in 1 to 7 days. We have used organ cultures to investigate mechanisms involved in this adaptation to mechanical load. Strips of rat portal vein were cultured for 3 days, either undistended or loaded by a weight. Length-force relations were shifted toward longer length in stretched cultured veins compared with freshly dissected veins, whereas the length-force relations of unstretched cultured veins were shifted in the opposite direction. This occurred after culture either with or without 10% FCS to promote growth. The wet weight of loaded veins increased by 56% in the presence of FCS, whereas that of undistended control veins increased by 24%. No weight increase was seen in serum-free culture. The dry/wet weight ratio decreased during culture with FCS but was not affected by stretch. Electron microscopy revealed increased cell cross-sectional area in stretched relative to unstretched veins, and protein contents were greater, as were [(3)H]thymidine and [(3)H]leucine incorporation rates. Growth responses were associated with the activation of stretch-sensitive extracellular signal-regulated kinases 1 and 2 and were inhibited by herbimycin A and PD 98059, inhibitors of extracellular signal-regulated kinases 1 and 2. The results demonstrate that by culture of whole vascular tissue, smooth muscle cells are maintained in the contractile phenotype and respond to stretch with a physiological adaptation involving hypertrophy/hyperplasia and remodeling of the contractile system, similar to that in vivo. Mechanical stimulation and growth factors are both required for functionally significant growth.

Animals↗
PubMed1986

Exercise training following cardiovascular surgery.

The patient following cardiovascular surgery is a special, and probably somewhat easier, problem for the rehabilitation team than post-MI or angina patients. These patients may generally be viewed as somewhat more stable than post-MI patients. Rehabilitation thus focuses on minimization of bed rest, treatment of the sequale of sternotomy, and surveillance for new or changing medical problems. Physiological adaptations to training are likely to parallel those observed with post-MI patients, except that evidence of improved myocardial perfusion is less likely to be observed. Although GXT may be useful to evaluate progress in rehabilitation, it is unlikely to yield meaningful information regarding the adequacy of the surgical result. The possibility for exercise programs/risk factor modification as a vehicle for secondary prevention following CABGS is about as likely, and as well supported by the available literature, as it is following MI. Secondary prevention studies following other types of cardiovascular surgery are not available.

Angioplasty, Balloon↗