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At least 469 records · Page 26Linked to original sources
PubMed1999

Uteroplacental hemostasis in intrauterine fetal growth retardation.

During pregnancy, extensive hemostatic changes occur in the uteroplacental circulation. Invading endovascular trophoblast cells induce physiological adaptations of uterine spiral arteries, required to accommodate the increased maternal blood flow to the intervillous space of the placenta as pregnancy advances. Much of the vascular endothelium and the underlying medial smooth muscle is replaced by trophoblasts, and fibrin or fibrinoid forms a major morphological feature of the arterial walls. Compared with endothelial cells, the trophoblast lining decidual spiral arteries have a reduced capacity to lyse fibrin, and recent studies have shown this to be caused by high levels of plasminogen activator inhibitors (PAI-1 and PAI-2). In pregnancies complicated by intrauterine fetal growth retardation (IUGR), with or without superimposed preeclampsia, a restricted physiological adaptation of uteroplacental spiral arteries is coupled with vascular lesions containing increased fibrin deposition. Significantly higher levels of PAI-1 are found in blood from the uterine vein at delivery and in tissue extracts of the placenta in these pregnancies than are found in normal pregnancy. Recent tissue culture studies have provided new information on the role of trophoblast cells in maintaining hemostatic control in the uteroplacental circulation in pregnancy. Cytotrophoblast cells isolated from the placenta and placental bed from IUGR pregnancies express significantly higher levels of PAI-1, coupled with a significant decrease in plasminogen activator activity, compared with trophoblast cells from normal pregnancy maintained in culture. This localized increased production of PAI-1 may play an important part in restricting endovascular trophoblast invasion in early pregnancy and increasing fibrin deposition and reducing uteroplacental blood flow in pregnancies complicated by IUGR.

Female↗
PubMed2005

Evolutionary relationships among squids of the family Gonatidae (Mollusca: Cephalopoda) inferred from three mitochondrial loci.

The oceanic squid family Gonatidae (Mollusca: Cephalopoda) is widely distributed in subpolar and temperate waters, exhibiting behavioral and physiological specializations associated with reproduction. Females of several species undergo muscular degeneration upon maturation; origins of this complex morphogenic change are unknown, hindering our understanding of ecological and morpho-physiological adaptations within the family. To provide further information regarding the evolutionary relationships within Gonatidae, three mitochondrial loci (12S rRNA, 16S rRNA, and cytochrome c oxidase subunit I) were analyzed for 39 individuals representing fourteen gonatid and six outgroup cephalopod species. In addition to elucidating relationships among gonatids, molecular data provided more information than morphological data for problematic specimens. Although some data sets are incongruent or have low nodal support values, combined molecular analysis confirms the presence of gonatid groups previously established by morphological characteristics (i.e., possessing radular teeth in seven longitudinal rows and muscular mantle tissue). These characteristics are basal to taxa possessing radular teeth in five longitudinal rows and less muscular mantle tissue, indicating that the derived forms are those species exhibiting physiological adaptation such as tissue degeneration upon maturation and egg brooding.

Animals↗
PubMed1993

Effects of water restriction on digestive function in two macropodid marsupials from divergent habitats and the feral goat.

The effects of water restriction on digestive function in the euro (Macropus robustus erubescens) found in the arid zone of inland Australia, the eastern wallaroo (M.r.robustus) from more mesic regions of eastern Australia, and the feral goat (Capra hircus) found throughout the range of M. robustus, were compared in order to examine some physiological adaptations required by herbivores for the exploitation of arid environments. Eight animals of each species were held in individual metabolism cages in temperature-moderated rooms and given a chopped hay diet ad libitum. Half the animals were restricted to 40 ml water.kg-0.80.day-1. This was 40%, 32% and 57% of voluntary drinking water intake in the euro, wallaroo and goat, respectively. All species responded to water restriction by reducing faecal, urinary and evaporative water losses in association with reductions in feed intake. All animals increased urine osmolality and electrolyte concentrations but not to maximal levels, while packed-cell volume and plasma osmolality and electrolyte concentrations were unaffected by water restriction. The euro displayed a suite of characteristics that separated it from the wallaroo in terms of physiological adaptation, including lower voluntary water intake, an increase in fibre digestibility and maintenance of nitrogen balance during water restriction, and lower faecal water efflux associated with a consistently lower faecal water content (54% versus 59% water in the wallaroo during water restriction, P < 0.05). The euro's colon was 37% longer (P < 0.01) than that of the wallaroo. The goat had the lowest faecal water efflux (P < 0.05) and the longest colon (P < 0.001). Water restriction did not affect water content in digesta, nor short-chain fatty acid concentrations or production rates in vitro. Total body water, as a proportion of body mass, was depressed (P < 0.05) in the macropodids, but not in the goat. The reduction in dietary nitrogen intake, which accompanied water restriction, was partially compensated by an increase in urea degradation in the gut from 68% to 76% of urea synthesis water-restricted macropodids. These responses to water restriction are discussed in relation to those reported in other macropodid and ruminant species.

Animals↗
PubMed1999

Perspective on the consequences of short- and long-duration space flight on human physiology.

During the past three decades, humans have made significant progress in accomplishing their aspirations for exploring the Moon and the planets. It is now appreciated that humans undergo a remarkable number of physiologic adaptations in microgravity that affect most physiologic systems. Space motion sickness was one of the first adaptations that humans experienced in microgravity. However, it is self-limiting and, most of the time, is effectively treated pharmacologically. Of particular concern is that, in microgravity, there is marked wasting of the skeletal musculature and skeleton that appears to be unrelenting and could impact on the health and welfare of space travelers during prolonged space flights and on return to earth. Microgravity also has a significant impact on the cardiovascular system that could have potentially serious consequences in terms of cardiovascular health during long-duration space flights. Other adaptations such as decreased T-cell responsiveness and changes in circadian rhythms is only now being explored. We need to understand the role that microgravity has on human physiologic systems in order to develop strategies for permitting humans to experience prolonged microgravity without having significant impact on their health and welfare. Engineering some gravitational force as a component of long-duration space vehicles should be given a high priority.

Adaptation, Physiological↗
PubMed2002

Inspiratory muscle training in patients with chronic obstructive pulmonary disease: structural adaptation and physiologic outcomes.

The present study was aimed at evaluating the effects of a specific inspiratory muscle training protocol on the structure of inspiratory muscles in patients with chronic obstructive pulmonary disease. Fourteen patients (males, FEV1, 24 +/- 7% predicted) were randomized to either inspiratory muscle or sham training groups. Supervised breathing using a threshold inspiratory device was performed 30 minutes per day, five times a week, for 5 consecutive weeks. The inspiratory training group was subjected to inspiratory loading equivalent to 40 to 50% of their maximal inspiratory pressure. Biopsies from external intercostal muscles and vastus lateralis (control muscle) were taken before and after the training period. Muscle samples were processed for morphometric analyses using monoclonal antibodies against myosin heavy chain isoforms I and II. Increases in both the strength and endurance of the inspiratory muscles were observed in the inspiratory training group. This improvement was associated with increases in the proportion of type I fibers (by approximately 38%, p < 0.05) and in the size of type II fibers (by approximately 21%, p < 0.05) in the external intercostal muscles. No changes were observed in the control muscle. The study demonstrates that inspiratory training induces a specific functional improvement of the inspiratory muscles and adaptive changes in the structure of external intercostal muscles.

Breathing Exercises↗
PubMed1997

Caffeine-resistance in S. pombe: mutations in three novel caf genes increase caffeine tolerance and affect radiation sensitivity, fertility, and cell cycle.

Caffeine is a well known base analogue and is cytotoxic to both animal and yeast cells. There are two possible mechanisms by which yeast cells tolerate caffeine concentrations higher than normal, by mutation or by physiological adaptation. We have isolated novel caffeine-resistant mutants of S. pombe which define three distinct genes caf2, caf3 and caf4. These mutants achieved a level of caffeine resistance which is presumed to represent the upper limit attainable by mutation. The caf2-caf4 mutations, as well as the previously identified caf1 mutation, confer UV-sensitivity, caffeine-resistant UV repair, impaired fertility and sporulation, as well as a lengthened cell cycle. They are partially dominant for caffeine resistance and recessive for UV sensitivity. Some auxotrophic caf3-89 double mutants show drastically decreased caffeine resistance. The caf4 mutant is more resistant to gamma-radiation than wild-type cells and shows pH-sensitive growth. As each caf mutation can, individually, confer maximum caffeine resistance to the cells, all four genes are expected to operate in the same pathway. This pathway might also be responsible for the physiological adaptation since adaptation is lost in caf1-caf4 mutants.

Caffeine↗
PubMed2007

Molybdenum intake influences molybdenum kinetics in men.

The objectives of this study were to determine physiologic adaptations that occur when humans are exposed to a wide range of molybdenum intake levels and to identify the pathways that are influenced by dietary intake. Four males consumed each of 5 daily molybdenum intakes of 22, 72, 121, 467, and 1490 microg/d (0.23, 0.75, 1.3, 4.9, and 15.5 micromol/d) for 24 d each. During each treatment period, oral and intravenous doses of (100)Mo and (97)Mo were administered. Serial plasma, urine, and fecal samples were analyzed for labeled and unlabeled molybdenum. Compartmental modeling was used to determine rates of distribution and elimination at each dietary intake level. Three pathways were sensitive to daily molybdenum intake. With increasing intake, absorption and urinary molybdenum excretion increased, whereas the fraction deposited in tissues decreased. Kinetic analysis suggested a daily intake of 115-120 microg/d (1.20-1.25 micromol/d) would maintain initial plasma molybdenum levels at their prestudy values and that their prestudy dietary intake was well above the Recommended Dietary Allowance of 45 microg/d. The physiological adaptations to changing intake that the model demonstrated may help prevent molybdenum deficiency and toxicity.

Administration, Oral↗
PubMed2005

Proteomic analysis of bovine skeletal muscle hypertrophy.

Myostatin plays a major role in muscle growth and development and animals with disruption of this gene display marked increases in muscle mass. Little is known about muscle physiological adaptations in relation to this muscle hypertrophy. To provide a more comprehensive view, we analyzed bovine muscles from control, heterozygote and homozygote young Belgian blue bulls for myostatin deletion, which results in a normal level of inactive myostatin. Heterozygote and homozygote animals were characterized by a higher proportion of fast-twitch glycolytic fibers in Semitendinosus muscle. Differential proteomic analysis of this muscle was performed using two-dimensional gel electrophoresis followed by mass spectrometry. Thirteen proteins, corresponding to 28 protein spots, were significantly altered in response to the myostatin deletion. The observed changes in protein expression are consistent with an increased fast muscle phenotype, suggesting that myostatin negatively controls mainly fast-twitch glycolytic fiber number. Finally, we demonstrated that differential mRNA splicing of fast troponin T is altered by the loss of myostatin function. The structure of mutually exclusive exon 16 appears predominantly expressed in muscles from heterozygote and homozygote animals. This suggests a role for exon 16 of fast troponin T in the physiological adaptation of the fast muscle phenotype.

Animals↗
PubMed2002

Assessment of right heart function in the athlete's heart.

It is known that the heart of an athlete has been physiologically adapted by prolonged training. There are a large number of echocardiographic studies which have focused on left ventricular wall thickness and dilatation, but there are few studies concerning right heart function in the athlete's heart. The aim of this study was to assess right heart function in elite athletes by conventional and new echocardiographic methods. The study population consisted of 36 elite highly-trained male athletes and 16 age-matched healthy sedentary controls. Right atrial, right ventricular, and inferior vena cava dimensions, and pulsed Doppler measurements of tricuspid inflow and right ventricular outflow were obtained, and systolic (preejection period, ejection time, preejection time/ejection time, QV peak, isovolumic contraction time) and diastolic (E peak, A peak, E/A ratio, decelaration time, isovolumic relexation time) function parameters were measured. The myocardial performance index was calculated as (isovolumetric contraction time + isovolumetric relaxation time)/ejection time. In addition, right ventricular systolic and diastolic functions were determined by Pulsed wave tissue Doppler imaging (S, E, and A velocities) at the lateral corners of the tricuspid annulus. The left ventricular mass index (P < 0.005), and right atrial (P < 0.001), right ventricular (P < 0.001), and inferior vena cava dimensions (P < 0.001) were significantly greater in athletes than in controls. Tricuspid E peak, A peak, E/A ratio, deceleration time, isovolumic relaxation time, preejection period, right ventricular ejection time, preejection time/ejection time, isovolumic contraction time, QV peak, and myocardial performance index were found to be similar in athletes and in controls (P > 0.05). Systolic, early diastolic, and late diastolic tissue Doppler imaging velocities were not significantly different in athletes and controls (P > 0.05). Left ventricular hypertrophy (LV mass index >134 g/m2) was found in 15 of the athletes. Right atrial dimension was greater in the athletes with left ventricular hypertrophy than in those without hypertrophy (P < 0.05). All right ventricular systolic and diastolic echocardiographic parameters were similar in athletes with and without left ventricular hypertrophy (P > 0.05). The results of this study indicate that right ventricular systolic and diastolic functions do not deteriorate in the athlete's heart despite significant chamber dilatation. They suggest that these changes are a normal physiologic adaptation to prolonged training.

Adult↗
PubMed2026

Potential Links Between Physiological and Perceptual Strain in High Heat Stress.

The physiological strain index (PhSI) is widely used to quantify thermoregulatory and cardiovascular strain during heat stress. However, direct physiological measurements may not always be feasible in occupational or athletic settings. Therefore, this study aimed to examine the relationship and agreement between perceptual strain and integrated physiological strain indices during high heat stress. Ten healthy, physically active, non-heat-acclimated males (29 (7) yr; 1.79 (0.11) m; 77.4 (9.3) kg) completed two randomized crossover exercise trials in hot-dry (HD) and warm-humid (WH) environments with equivalent wet-bulb globe temperatures. Heart rate, rectal temperature, skin temperature, rating of perceived exertion, and thermal sensation were measured at baseline and every 15&#xa0;minutes during 60&#xa0;minutes of cycling. Physiological strain index (PhSI), adaptive physiological strain index (aPhSI), and perceptual strain index (PeSI) were calculated using validated equations. Repeated-measures correlation analyses demonstrated very strong associations between PeSI and both PhSI and aPhSI under HD (Rrm&#xa0;=&#xa0;0.940-0.943) and WH (Rrm&#xa0;=&#xa0;0.980-0.982; all p&#xa0;<&#xa0;0.001). Receiver operating characteristic analyses demonstrated good-to-excellent discrimination of physiological strain by PeSI (AUC&#xa0;=&#xa0;0.895-0.969). Mixed-effects analyses showed that higher PeSI values were associated with increased PhSI (&#x3b2;&#xa0;=&#xa0;1.325, p&#xa0;<&#xa0;0.001) and aPhSI (&#x3b2;&#xa0;=&#xa0;1.459, p&#xa0;<&#xa0;0.001). However, Bland-Altman analyses demonstrated relatively small mean biases (0.4-0.9 AU) but wide limits of agreement (-2.8 to 4.2 AU), indicating that PeSI and physiological strain indices are not interchangeable. These findings suggest that PeSI may serve as a practical adjunctive or screening indicator of physiological strain when direct physiological measurements are unavailable.

Humans↗
PubMed1990

The physiology of adaptation to small bowel resection in the pig: an integrated study of morphological and functional changes.

This study examined the adaptive response to extensive small intestinal resection in the juvenile domestic pig. Control animals underwent an ileal transection with end-to-end anastomosis, whereas resected pigs had a resection of the mid-75% of the total small bowel length. Animals were followed for 16 weeks. Resected animals gained less weight than controls, with no significant difference in feed intake per unit animal weight. In vivo fat, protein, carbohydrate, and total energy absorption were reduced in resected animals. Resected pigs had increased in vitro passive ileal uptake of fatty acids, cholesterol, and L-glucose, but no change in active D-glucose uptake. Microscopic morphology was altered, with an increase in the size of villi, a decrease in villous density, and no net change in mucosal surface area per unit of serosal surface area. Gross bowel length and diameter increased proportionately more in the resected than the control groups. This study demonstrated that massive resection results in a significant change in nutritional status in the growing pig. Functional and morphological changes occur, demonstrating intestinal adaptation. These findings suggest that this model would be suitable for the study of therapeutic modalities for the short-bowel syndrome in humans.

Animals↗
PubMed1988

Adaptations in lip posture and pressure following orthognathic surgery.

Lip pressures before and after orthognathic surgery were studied to evaluate the relationship between posttreatment soft-tissue adaptation and incisor stability. After all surgical procedures, physiologic adaptation resulted in the maintenance of pressures during speech and swallowing. When the maxilla was advanced by LeFort I osteotomy, a significant decrease in resting pressure of the upper lip was observed instead of the expected increase and incisor stability did not seem related to soft-tissue influences. When the mandible was advanced by sagittal split osteotomy, resting pressure did not increase as expected, but there was a tendency for incisors to become more upright after fixation release, perhaps as a rebound from labial tipping in fixation. When soft tissues were relaxed as the mandible rotated forward following superior repositioning of the maxilla, resting pressures decreased and lower incisors tended to be positioned forward as predicted by equilibrium theory.

Adaptation, Physiological↗