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Human physiological adaptation to pregnancy: inter- and intraspecific perspectives.

Reproductive success requires successful maternal physiological adaptation to pregnancy. An interspecific perspective reveals that the human species has modified features of our haplorhine heritage affecting the uteroplacental circulation. We speculate that such modifications - including early implantation and deep, widespread invasion of fetal (trophoblast cells) into and resultant remodeling of maternal uterine vessels - are responses to or compensation for the biomechanical constraints imposed by bipedalism which, in turn, render our species susceptible to the pregnancy complication of preeclampsia. Preeclampsia is characterized by incomplete remodeling of maternal uterine vessels as the result of shallow trophoblast invasion, which in turn reduces uteroplacental blood flow and frequently leads to intrauterine growth restriction (IUGR). Using an intraspecific perspective, we consider the fitness-related consequences of variation in uteroplacental blood flow during high-altitude pregnancy. Although birth weights are reduced at high altitudes in Bolivia, multigenerational Andean residents are relatively protected from altitude-associated IUGR. Our preliminary data suggest that Andean women have greater uteroplacental oxygen delivery than European high-altitude residents due to more complete growth and remodeling of maternal uterine vessels. Identification of the physiological and genetic mechanisms involved in such inter- and intraspecific variations in pregnancy physiology will likely be useful for understanding human evolution and contemporary challenges to successful reproduction.

Adaptation, Physiological↗
PubMed2005

Differential gene expression by Metarhizium anisopliae growing in root exudate and host (Manduca sexta) cuticle or hemolymph reveals mechanisms of physiological adaptation.

Like many other fungal pathogens Metarhizium anisopliae is a facultative saprophyte with both soil-dwelling and insect pathogenic life-stages. In addition, as M. anisopliae traverses the cuticle and enters the hemolymph it must adapt to several different host environments. In this study, we used expressed sequence tags and cDNA microarray analyses to demonstrate that physiological adaptation by M. anisopliae to insect cuticle, insect hemolymph, bean root exudate (a model for life in the soil), and nutrient rich Sabouraud dextrose broth (SDB) involves different subsets of genes. Overall, expression patterns in cuticle and hemolymph clustered separately from expression patterns in root exudates and SDB, indicative of critical differences in transcriptional control during pathogenic and saprophytic growth. However, there were differences in gene expression between hemolymph and cuticle and these mostly involved perception mechanisms, carbon metabolism, proteolysis, cell surface properties, and synthesis of toxic metabolites. These differences suggest previously unsuspected stratagems of fungal pathogenicity that can be tested experimentally. Examples include the switch-off of cuticle-degrading proteases and a dramatic cell wall reorganization during growth in hemolymph.

Adaptation, Physiological↗
PubMed1993

Caffeine tolerance in Schizosaccharomyces pombe: physiological adaptation and interaction with theophylline.

Caffeine at concentrations of 8 mM or higher inhibited cell propagation and killed a fraction of the population. Cell inactivation increased incrementally with increasing concentrations. The survivors developed tolerance by physiological adaptation that enabled them to propagate in the presence of the drug, but the tolerance could easily be lost if the cells grew in the absence of caffeine for a few generations. Theophylline was found to diminish the toxic effect of caffeine. Possible mechanisms for the observed cellular response and its implications for studies of the effects of these drugs in eukaryotes are discussed.

Adaptation, Physiological↗
PubMed2005

Physiological adaptations to soccer specific endurance training in professional youth soccer players.

BACKGROUND: Improved oxygen uptake improves soccer performance as regards distance covered, involvements with the ball, and number of sprints. Large improvements in oxygen uptake have been shown using interval running. A similar physiological load arising from interval running could be obtained using the soccer ball in training. OBJECTIVES: The main aim was to study physiological adaptations to a 10 week high intensity aerobic interval training program performed by professional youth soccer players, using a soccer specific ball dribbling track. METHODS: Eleven youth soccer players with a mean (SD) age of 16.9 (0.4) years performed high intensity aerobic interval training sessions twice per week for 10 weeks in addition to normal soccer training. The specific aerobic training consisted of four sets of 4 min work periods dribbling a soccer ball around a specially designed track at 90-95% of maximal heart frequency, with a 3 min recovery jog at 70% of maximal heart frequency between intervals. RESULTS: Mean VO2max improved significantly from 63.4 (5.6) to 69.8 (6.6) ml kg(-1) min(-1), or 183.3 (13.2) to 201.5 (16.2) ml kg(-0.75) min(-1) (p<0.001). Squat jump and counter movement jump height increased significantly from 37.7 (6.2) to 40.3 (6.1) cm and 52.0 (4.0) to 53.4 (4.2) cm, respectively (p<0.05). No significant changes in body mass, running economy, rate of force development, or 10 m sprint times occurred. CONCLUSION: Performing high intensity 4 min intervals dribbling a soccer ball around a specially designed track together with regular soccer training is effective for improving the VO2max of soccer players, with no negative interference effects on strength, jumping ability, and sprinting performance.

Adaptation, Physiological↗
PubMed1989

The effect of detraining and reduced training on the physiological adaptations to aerobic exercise training.

In previously sedentary individuals, regularly performed aerobic exercise results in significant improvements in exercise capacity. The development of peak exercise performance, as typified by competitive endurance athletes, is dependent upon several months to years of aerobic training. The physiological adaptations associated with these improvements in both maximal exercise performance, as reflected by increases in maximal oxygen uptake (VO2max), and submaximal exercise endurance include increases in both cardiovascular function and skeletal muscle oxidative capacity. Despite prolonged periods of aerobic training, reductions in maximal and submaximal exercise performance occur within weeks after the cessation of training. These losses in exercise performance coincide with declines in cardiovascular function and muscle metabolic potential. Significant reductions in VO2max have been reported to occur within 2 to 4 weeks of detraining. This initial rapid decline in VO2max is likely related to a corresponding fall in maximal cardiac output which, in turn, appears to be mediated by a reduced stroke volume with little or no change in maximal heart rate. A loss in blood volume appears to, at least partially, account for the decline in stroke volume and VO2max during the initial weeks of detraining, although changes in cardiac hypertrophy, total haemoglobin content, skeletal muscle capillarisation and temperature regulation have been suggested as possible mediating factors. When detraining continues beyond 2 to 4 weeks, further declines in VO2max appear to be a function of corresponding reductions in maximal arterial-venous (mixed) oxygen difference. Whether reductions in oxygen delivery to and/or extraction by working muscle regulates this progressive decline is not readily apparent. Changes in maximal oxygen delivery may result from decreases in total haemoglobin content and/or maximal muscle blood flow and vascular conductance. The declines in skeletal muscle oxidative enzyme activity observed with detraining are not causally linked to changes in VO2max but appear to be functionally related to the accelerated carbohydrate oxidation and lactate production observed during exercise at a given intensity. Alternatively, reductions in submaximal exercise performance may be related to changes in the mean transit time of blood flow through the active muscle and/or the thermoregulatory response (i.e. degree of thermal strain) to exercise. In contrast to the responses observed with detraining, currently available research indicates that the adaptations to aerobic training may be retained for at least several months when training is maintained at a reduced level. Reductions of one- to two-thirds in training frequency and/or duration do not significantly alter VO2max or submaximal endurance time provided the intensity of each exercise session is maintained.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗
PubMed1992

Physiological adaptations to velocity-controlled resistance training.

The force-velocity characteristics of skeletal muscle are such that maximal force is inversely related to the velocity of shortening. This relationship has been observed using isolated muscle preparations and intact muscle groups (e.g. knee extensors). Isokinetic dynamometry has revealed some specific physiological adaptations to different velocities of training: an increase in torque and power that are greater at or near the velocity of training; a transfer of torque gains to slower and faster angular velocities after intermediate velocity resistance training; increases in maximal oxygen consumption and cardiac output in response to circuit training; increases in anaerobic power output; changes in skeletal muscle size and changes in myofibrillar ATPase activity; and new applications for rehabilitation of muscular and ligamentous injuries, and post-coronary patients.

Adaptation, Physiological↗
PubMed2002

Hibernating without oxygen: physiological adaptations of the painted turtle.

Many freshwater turtles in temperate climates may experience winter periods trapped under ice unable to breathe, in anoxic mud, or in water depleted of O(2). To survive, these animals must not only retain function while anoxic, but they must do so for extended periods of time. Two general physiological adaptive responses appear to underlie this capacity for long-term survival. The first is a coordinated depression of metabolic processes within the cells, both the glycolytic pathway that produces ATP and the cellular processes, such as ion pumping, that consume ATP. As a result, both the rate of substrate depletion and the rate of lactic acid production are slowed greatly. The second is an exploitation of the extensive buffering capacity of the turtle's shell and skeleton to neutralize the large amount of lactic acid that eventually accumulates. Two separate shell mechanisms are involved: release of carbonate buffers from the shell and uptake of lactic acid into the shell where it is buffered and sequestered. Together, the metabolic and buffering mechanisms permit animals to survive for 3-4 months at 3 degrees C with no O(2) and with circulating lactate levels of 150 mmol l(-1) or more.

Adaptation, Physiological↗
PubMed1999

Physiological adaptations to space flight.

Over the last 30 years, humans have extended their stays in space from a brief suborbial flight of 15 minutes to an orbital residence of 440+ days. Complex spacecraft now routinely transport humans into an environment more forbidding than any previously encountered. Nutrition can play an important role in counteracting some of the physiological effects of microgravity, and have a profound effect on the quality of life in space. As we embark on extended-duration flights, nutrition becomes a critical issue. This article reviews the physiological adaptations to space flight that affect nutritional requirements.

Adaptation, Physiological↗
PubMed2004

Klebsiella planticola strain DSZ mineralizes simazine: physiological adaptations involved in the process.

We examined the ability of a soil bacterium, Klebsiella planticola strain DSZ, to degrade the herbicide simazine (SZ). Strain DSZ is metabolically diverse and grows on a wide range of s-triazine and aromatic compounds. DSZ cells grown in liquid medium with SZ (in 10 mM ethanol) as carbon source mineralized 71.6+/-1.3% of 0.025 mM SZ with a yield of 4.6+/-0.3 microg cell dry weight mmol(-1) carbon. The metabolites produced by DSZ during SZ degradation included ammeline, cyanuric acid, N-formylurea and urea. We studied the physiological adaptations which allow strain DSZ to metabolize SZ. Using scanning electron microscopy, we detected DSZ cells covering the surfaces of SZ crystals when the herbicide was used at high concentrations (0.1 mM). The membrane order observed by FTIR spectroscopy showed membrane activity at low temperature (4 degrees C) to assimilate the herbicide. Membrane fatty acid analysis demonstrated that strain DSZ adapted to grow on SZ by increasing the degree of saturation of membrane lipid fatty acid; and the opposite effect was detected when both SZ and ethanol were used as carbon sources. This confirms the modulator effect of ethanol on membrane fluidity.

Adaptation, Physiological↗
PubMed2001

Physiological adaptation of crop plants to flooding stress.

When crop plants are subjected to soil waterlogging, or an anaerobic condition, their root and shoot systems respond differently. A variety of morphological and anatomical alterations develop in the root system. Reduction of the root respiration rate has been reported in both flooding-tolerant and intolerant species. Besides alcoholic fermentation, several diverse fermentative bypasses take place, which ameliorate the poisoning through excessive accumulation of specific metabolic intermediates. Root systems starved of oxygen are also poor providers of mineral nutrients for both themselves and the shoot systems. Stomatal closure and non-stomatal metabolic alterations are responsible for the reduction of leaf CO2 incorporation. Plant hormones are much involved in regulation of these physiological adaptations.

Adaptation, Physiological↗
PubMed2003

Is visceral obesity a physiological adaptation to stress?

Visceral obesity represents an important risk factor associated with hypertension, diabetes and cardiovascular diseases. Since this condition is associated with a disruption of the functioning of the HPA axis, stress-induced HPA axis activation has been identified to play an important role in this preferential body fat accumulation. HPA axis activation increases cortisol (corticosterone) production which has been shown to exert hyperphagic and antithermogenic effects. Since abdominal adipose tissue has more cells per mass units, higher blood flow and more glucocorticoid receptors, glucocorticoids affect abdominal fat to a greater extent than subcutaneous adipose tissue. Cushing's syndrome in humans is the best evidence showing a link between hypercortisolemia and accumulation of central fat. The Hervey's hypothesis which suggests that fat cells take up and catabolize glucocorticoids is one of the possible regulatory effect that supports the adaptive role of visceral fat in response to stress. This is also supported by other evidence showing that abdominal obesity is associated with an increased cortisol clearance. Hormonal and enzymatic changes have been implicated in this preferential body fat accumulation in response to stress. Specific genetic background may also accentuate this visceral fat accumulation in some individuals exposed to stress. Alternatively, obesity could also be a source of stress promoting the visceral fat accumulation since visceral fat is able to release cytokines which stimulate the HPA axis. Even if the available literature does not permit to establish clearly which comes first, it suggests that visceral obesity could represent a non optimal physiological adaptation to stress. In this context, visceral obesity treatment should focus on stress management and weight loss strategies in order to stop this vicious circle.

Abdomen↗
PubMed2006

Physiological adaptation in early human pregnancy: adaptation to balance maternal-fetal demands.

After conception, the corpus luteum, placenta, and developing embryo release hormones, growth factors, and other substances into the maternal circulation. These substances trigger a cascade of events that transform the functioning of the maternal cardiovascular, respiratory, and renal systems, which in turn alter the physicochemical determinants of [H(+)]. Following implantation, maternal adaptations fulfill 4 important functions that support fetal growth. Increased availability of substrates and precursors for fetal-placental metabolism and hormone production is mediated by increases in dietary intake, as well as endocrine changes that increase the availability of glucose and low-density lipoprotein (LDL) cholesterol. Transport capacity is enhanced by increases in cardiac output, facilitating the transport of substrates and precursors to the placenta, and fetal waste products to maternal organs for disposal. Maternal-fetal exchange is regulated by the placenta after 10-12 weeks gestation, but it may occur through histiotrophic mechanisms before this time. Disposal of additional waste products (heat, carbon dioxide, and metabolic byproducts) occurs through peripheral vasodilation and increases in skin blood flow, ventilation, and renal filtration. The maternal physiological adaptations described above must meet the combined demands of maternal exercise and fetal growth. More research is needed to formulate evidence-based guidelines for healthy physical activity in early pregnancy.

Adaptation, Physiological↗
PubMed2000

Dietary composition and physiologic adaptations to energy restriction.

BACKGROUND: The concept of a body weight set point, determined predominantly by genetic mechanisms, has been proposed to explain the poor long-term results of conventional energy-restricted diets in the treatment of obesity. OBJECTIVE: The objective of this study was to examine whether dietary composition affects hormonal and metabolic adaptations to energy restriction. DESIGN: A randomized, crossover design was used to compare the effects of a high-glycemic-index (high-GI) and a low-glycemic-index (low-GI) energy-restricted diet. The macronutrient composition of the high-GI diet was (as percent of energy) 67% carbohydrate, 15% protein, and 18% fat and that of the low-GI diet was 43% carbohydrate, 27% protein, and 30% fat; the diets had similar total energy, energy density, and fiber contents. The subjects, 10 moderately overweight young men, were studied for 9 d on 2 separate occasions. On days -1 to 0, they consumed self-selected foods ad libitum. On days 1-6, they received an energy-restricted high- or low-GI diet. On days 7-8, the high- or low-GI diets were consumed ad libitum. RESULTS: Serum leptin decreased to a lesser extent from day 0 to day 6 with the high-GI diet than with the low-GI diet. Resting energy expenditure declined by 10.5% during the high-GI diet but by only 4.6% during the low-GI diet (7.38 +/- 0.39 and 7.78 +/- 0.36 MJ/d, respectively, on days 5-6; P = 0.04). Nitrogen balance tended to be more negative, and energy intake from snacks on days 7-8 was greater, with the high-GI than the low-GI diet. CONCLUSION: Diets with identical energy contents can have different effects on leptin concentrations, energy expenditure, voluntary food intake, and nitrogen balance, suggesting that the physiologic adaptations to energy restriction can be modified by dietary composition.

Adaptation, Physiological↗
PubMed1986

Physiological adaptability: the secret of success of the internal mammary artery grafts.

Angiographic studies in 3 patients illustrate the physiological adaptability of internal mammary artery (IMA) grafts. Intact vascular smooth muscle permits the IMA grafts to retain a flexible caliber and a blood flow dictated by myocardial demands in the distribution of the grafted coronary artery. This physiological nature may be one of the reasons for their continued patency regardless of whether they are grafted to large or small coronary arteries. Further, this adaptable behavior permits use of the IMA even if its distal lumen is smaller than that of the recipient coronary artery, provided the anastomosis can be safely performed and the demand for flow is present.

Coronary Disease↗
PubMed2001

Oxytocin facilitates behavioural, metabolic and physiological adaptations during lactation.

The aim of this article is to propose that oxytocin not only stimulates milk let down, but also adapts behaviour and physiology to facilitate lactation in mammals including dairy cattle. Circulating oxytocin as well as neurogenic oxytocin participates in these regulatory processes. In short, oxytocin stimulates maternal interaction and attachment between mother and young. It also participates in the metabolic prerequisites for milk production by e.g. stimulating glucagon release and thereby, mobilisation of glucose. Digestive and anabolic aspects of metabolism are also stimulated, e.g. by increased vagal nerve activity. Adaptations consistent with an antistress like pattern are also induced. Cortisol levels are decreased as well as blood pressure, and behaviours characterised by calm, reduced levels of anxiety and more social activity are promoted. These effects seem to be present in monogastric animals as well as in ruminants. The expression of various aspects of these adaptations vary according to the special needs and living environmental circumstances of different species. The mechanisms behind the effect spectrum of oxytocin are being explored in other experimental models. A second aim of this paper is to suggest that efficiency of lactation can be promoted by facilitating oxytocin release in connection with milking by enhancing the amount of sensory stimulation.

Journal Article↗
PubMed2003

Physiological adaptations of the gut in the Lake Magadi tilapia, Alcolapia grahami, an alkaline- and saline-adapted teleost fish.

We describe the gut physiology of the Lake Magadi tilapia (Alcolapia grahami), specifically those aspects associated with feeding and drinking while living in water of unusually high carbonate alkalinity (titratable base=245 mequiv l(-1)) and pH (9.85). Drinking of this highly alkaline lake water occurs at rates comparable to or higher than those seen in marine teleosts. Eating and drinking take place throughout the day, although drinking predominates during hours of darkness. The intestine directly intersects the esophagus at the anterior end of the stomach forming a 'T', and the pyloric sphincter, which comprises both smooth and striated muscle, is open when the stomach is empty and closed when the stomach is full. This unique configuration (a functional trifurcation) allows imbibed alkaline water to bypass the empty stomach, thereby avoiding a reactive mixing with acidic gastric fluids, and minimizes interference with a full stomach. No titratable base was present in the stomach, where the mean pH was 3.55, but the intestine was progressively more alkaline (foregut 6.96, midgut 7.74, hindgut 8.12, rectum 8.42); base levels in the intestinal fluid were comparable to those in lake water. The gut was highly efficient at absorbing water (76.6%), which accompanied the absorption of Na(+) (78.5%), titratable base (80.8%), and Cl(-) (71.8%). The majority of Na(+), base and water absorption occurred in the foregut by an apparent Na(+) plus base co-transport system. Overall, more than 70% of the intestinal flux occurred via Na(+) plus base co-transport, and less than 30% by Na(+) plus Cl(-) co-transport, a very different situation from the processes in the intestine of a typical marine teleost.

Adaptation, Physiological↗