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PubMed1999

Influence of photoperiod on immune cell functions in the male Siberian hamster.

The present study tested the hypothesis that immune cell function is influenced by ambient photoperiod. The male Siberian hamster served as the experimental model because day length regulates a variety of seasonal adaptations in physiology. Adult hamsters were in long days (16 h of light daily), which sustains gonadal function, or transferred to short days (8 h) for >4 wk to induce testes regression. Blood was drawn from the ocular sinus or splenocytes obtained to assess basal indexes of immune cell function. In hamsters in short days, natural killer cell cytolytic capacity, as well as spontaneous blastogenesis in both whole blood and isolated lymphocytes, were enhanced compared with that in hamsters in long days. By contrast, phagocytosis and oxidative burst activity by both granulocytes and monocytes were suppressed in hamsters by exposure to short days versus long days. Selective changes in immune cell function coincided with short-day-induced gonadal atrophy. These findings raise the hypothesis that photoperiod regulation of physiological adaptations, including distinct immune cell functions, may help individuals anticipate seasonal challenges posed by opportunistic diseases or climate to facilitate survival.

Animals↗

PubMed1986

Physiological profile of world-class high-altitude climbers.

The functional characteristics of six world-class high-altitude mountaineers were assessed 2-12 mo after the last high-altitude climb. Each climber on one or several occasions had reached altitudes of 8,500 m or above without supplementary O2. Static and dynamic lung volumes and right and left echocardiographic measurements were found to be within normal limits of sedentary controls (SC). Muscle fiber distribution was 70% type I, 22% type IIa, and 7% type IIb. Mean muscle fiber cross-sectional area was significantly smaller than that of SC (-15%) and of long-distance runners (LDR, -51%). The number of capillaries per unit cross-sectional area was significantly greater than that of SC (+ 40%). Total mitochondrial volume was not significantly different from that of SC, but its subsarcolemmal component was equal to that of LDR. Average maximal O2 consumption was 60 +/- 6 ml X kg-1 X min-1, which is between the values of SC and LDR. Average maximal anaerobic power was 28 +/- 2.5 W X kg-1, which is equal to that of SC and 40% lower that that of competitive high jumpers. All subjects were characterized by resting hyperventilation both in normoxia and in moderate (inspired O2 partial pressure = 77 Torr) hypoxia resulting in higher oxyhemoglobin saturation levels in hypoxia. The ventilatory response to four tidal volumes of pure O2 was similar to that of SC. It is concluded that elite high-altitude climbers do not have physiological adaptations to high altitude that justify their unique performance.

Adaptation, Physiological↗

PubMed2005

Effects of angiotensin-converting enzyme polymorphism on aortic elastic parameters in athletes.

BACKGROUND: Physiologic adaptations in an athlete's heart include increased left and right ventricular chamber size, left ventricular wall thickness and mass. Angiotensin-converting enzyme (ACE) is a key enzyme in angiotensin II production causing cardiac hypertrophy. The cloning of the ACE gene has made it possible to identify a deletion (D)-insertion (I) polymorphism that appears to affect the level of serum ACE activity. Therefore, the ACE genes, which have been shown to be polymorphic, could be candidate genes for large-artery stiffness. METHODS: 56 endurance athletes and 46 sedentary subjects were included in this study, and they underwent both complete echocardiographic examination, and analysis of ACE insertion (I) and deletion (D) allele frequencies in peripheral blood. The aortic diameter was recorded by M-mode echocardiography at a level 3 cm above the aortic valve. Aortic systolic diameter was measured at the time of full opening of the aortic valve, and diastolic diameter was measured at the peak of QRS. Aortic strain, stiffness index and distensibility were calculated. RESULTS: Left ventricular mass index and left ventricular ejection fraction were significantly higher in athletes than controls (p < 0.001). The aortic distensibility index and strain were significantly greater in athletes compared with controls (respectively: 5.8 +/- 2.7 vs. 4.7 +/- 1.8 cm(-2) dyn(-1) 10(-6), p = 0.017; 12.3 +/- 2.4 vs. 9.3 +/- 3.1, p < 0.001). The aortic stiffness index was significantly lower in athletes than in controls (4.8 +/- 1.9 vs. 6.1 +/- 2.1, p < 0.001). The aortic distensibility index and strain were statistically different in ACE DD vs. DI groups and DD vs. II groups of athletes. The aortic stiffness index was statistically different in ACE DD vs. II groups of athletes. Aortic parameters were similar according to ACE genotypes in controls. CONCLUSION: The results of this study indicate that aortic distensibility was increased by prolonged training in endurance athletes, particularly in those with the ACE II genotype. This effect represents an extracardiac adaptation to chronic prolonged training in athletes.

Adaptation, Physiological↗

PubMedDate not supplied

Neuroimmunomodulation in immune privilege: role of neuropeptides in ocular immunosuppression.

The microenvironments of the eye and brain are physiologically adapted to protect their delicate structures and functions from damaging immunogenic inflammation (delayed-type hypersensitivity). This adaptation is immune privilege. Aqueous humor, the fluid filling the ocular anterior chamber, suppresses antigen-stimulated primed T cells from mediating inflammation by inhibiting the production of the proinflammatory lymphokine interferon gamma. This suppression is mediated by immunosuppressive cytokines and neuropeptides constitutively produced in the eye and released into aqueous humor. Cerebrospinal fluid has similar immunosuppressive activities, cytokines, and neuropeptides as aqueous humor, indicating that similar mechanisms may mediate immune privilege in the eye and brain. The importance of neuropeptides in mediating immunosuppression indicates that immunosuppressive neuroimmunomodulation has a role in preventing induction of immunogenic inflammation within immune-privileged tissues.

Adaptation, Physiological↗

PubMed1979

Effect of short-term cold stress on the respiratory metabolism of brain tissue homogenates of male garden lizards of two different age-groups.

The endogenous oxygen uptake and the uptake with added substrate of whole-brain and mid-brain homogenates were significantly lower in older lizards as compared to younger. Both whole brain and mid-brain showed responses to cold stress for different lengths of time but the decline in oxygen uptake was more pronounced in the younger age-group. Respiratory rate and response to cold stress were more marked in the mid-brain than in the whole brain. Basing on earlier reports on mammals and on the present findings, it is suggested that the decline in physiological adaptation in older animals may be a general feature in vertebrates.

Adaptation, Physiological↗

PubMedDate not supplied

Fetal urine production rates following intrauterine transfusion.

This study investigates the hypothesis that following an intrauterine, intravascular transfusion (IVT), one of the physiologic adaptations might be an increase in the fetal urine production. The hourly fetal urine production rate (HFUPR) was measured for the first hour following 12 transfusions and for 24 h following 5 transfusions in anemic isoimmunized fetuses. The HFUPR was also measured in 5 control fetuses who underwent fetal blood sampling without transfusion. Fetal hemoglobin, hematocrit and blood viscosity were measured before and after each transfusion. The HFUPR fell significantly from a mean (SEM) of 19.2 (2.85) to 7.4 (2.2) ml/h, and remained low for at least 4 h posttransfusion returning to pretransfusion rates by 24 h. There was no change in the HFUPR in the control fetuses. The study suggests that in human fetuses the rapid excretion of excess fluid via the renal tract is not an acute adaptive response to an IVT.

Adaptation, Physiological↗

PubMedDate not supplied

Electrophysiological characteristics of the human atria after cardioversion of persistent atrial fibrillation.

BACKGROUND: In animal models, induced atrial fibrillation shortens the atrial effective refractory period (ERP) and reverses its physiological adaptation to rate. It is not clear whether this process, known as "electrical remodeling," occurs in humans. METHODS AND RESULTS: We determined the ERPs, at 5 pacing cycle lengths (300 to 700 ms) and in 5 right atrial sites, after internal cardioversion of chronic atrial fibrillation in 25 patients (14 in pharmacological washout and 11 on amiodarone). The ERPs were 195.5+/-18.8 ms in the washout and 206.3+/-17.9 ms in the amiodarone patients (P<0.0001). ERPs were closely correlated with the stimulation rates (r=0.95 in the washout and r=0.94 in the amiodarone group), and slope values indicating a normal (>/=0.07) or nearly normal (0.05 to 0.06) adaptation of ERP to rate were found in 77% of the 84 paced sites. The mean ERP was shorter in the lateral wall (198.1+/-17.9 ms) than in the atrial roof (203.3+/-21.5 ms) and in the septum (210.5+/-20.0 ms) (P<0.03). After 4 weeks of sinus rhythm, the mean ERP, determined again in 8 patients (4 in wash-out and 4 on amiodarone), was significantly increased compared with the basal study (221. 4+/-21.4 versus 197.8+/-18.3 ms, P<0.0001). CONCLUSIONS: After cardioversion of chronic atrial fibrillation, (1) atrial ERP adaptation to rate was normal or nearly normal in the majority of the cases, (2) a significant dispersion of refractoriness between different right atrial sites was present, and (3) ERPs were significantly increased after 4 weeks of sinus rhythm in both washout and amiodarone patients.

Adaptation, Physiological↗

PubMed1990

Differential effects of cardiac hypertrophy and failure on right versus left ventricular calcium activation.

We studied calcium responsiveness of skinned muscle preparations from the right and left ventricles of rats with cardiac hypertrophy and cardiac hypertrophy plus failure. To test the hypothesis that differences in contractile function are due to changes in myofilament calcium responsiveness, we compared preparations from spontaneously hypertensive rats with cardiac failure, spontaneously hypertensive rats without cardiac failure, and age-matched normotensive Wistar-Kyoto control rats 18-24 months of age. Rats with failure had pleural/pericardial effusions, left atrial thrombi, and right and left ventricular hypertrophy. Muscles were skinned by saponin (250 micrograms/ml) and activated with a series of calcium buffers. Data were plotted as pCa (-log[Ca2+]) versus isometric force and then fit to a modified Hill equation. Values for 50% maximal activation (calcium sensitivity), maximal calcium-activated force, and the slope of the calcium-force relation were compared. Our data indicate that with the development of hypertrophy, calcium sensitivity of left ventricular muscles remains unaffected, but maximal calcium-activated force is increased. In contrast, maximal calcium-activated force declines toward control levels with the development of left ventricular failure, despite the continued presence of significant hypertrophy. In the normotensive rats, the left ventricle is more sensitive to calcium than the right ventricle (pCa50 = 6.0 +/- 0.05 versus 5.7 +/- 0.09; p less than 0.05); however, both the calcium sensitivity and maximal calcium-activated force of the right ventricle increase with the development of compensatory hypertrophy secondary to left ventricular failure. These changes that occur in rats with cardiac hypertrophy and failure may represent important physiological adaptive mechanisms.

Actin Cytoskeleton↗

PubMed1984

Chemical carcinogenesis: hepatocyte nodules with a special phenotype as a common step at the crossroads.

Unlike the great heterogeneity and diversity in the initial interactions of a chemical carcinogen with DNA and in the phenotypes of the late malignant neoplasms, the intermediate steps in liver carcinogenesis, the hepatocyte nodules, are remarkably similar. This commonality is seen in six different models of liver cancer development using carcinogens and promoters of quite different chemical structure and properties. The hepatocytes in the nodules show a similar arrangement and architecture, cytology and cytochemistry, blood supply, biological behavior, and biochemical pattern. These observations, coupled with the program nature of the remodeling of the hepatocyte nodules, strongly suggest that at least some of the earlier steps in carcinogenesis are of a physiological adaptive nature.

Adaptation, Physiological↗

PubMed2001

The impact of microgravity on bone metabolism in vitro and in vivo.

Exposure to microgravity has been associated with several physiological changes in astronauts and cosmonauts, including an osteoporosis-like loss of bone mass. In-flight measures used to counteract this, including intensive daily exercise regimens, have been only partially successful in reducing the bone loss and in the process have consumed valuable work time. If this bone loss is to be minimized or, preferably, prevented, more effective treatment strategies are required. This, however, requires a greater understanding of the mechanisms through which bone metabolism is affected by microgravity. Various research strategies have been used to examine this problem, including in vitro studies using bone cells and in vivo studies on humans and rats. These have been conducted both in flight and on the ground, by strategies that produce weightlessness to mimic the effects of microgravity. Overall, the majority of the studies have found that marked decreases in gravitation loading result in the loss of bone mass. The processes of bone formation and bone resorption become uncoupled, with an initial transitory increase in resorption accompanied by a prolonged decrease in formation. Loss of bone mass is not uniform throughout the skeleton, but varies at different sites depending on the type of bone and on the mechanical load received. It appears that the skeletal response is a physiologic adaptation to the space environment which, after long space flights or repeated shorter ones, could eventually lead to significant reductions in the ability of the skeletal tissues to withstand the forces of gravity and increased susceptibility to fracture.

Adaptation, Physiological↗

PubMed2005

Role of occlusal vertical dimension in spindle function.

Several studies have suggested the jaw-muscle spindle as the receptor responsible for regulating and maintaining the occlusal vertical dimension (OVD). However, to challenge this assumption, we hypothesized that long-term changes in OVD could affect the sensory inputs from jaw-muscle spindles. In this study, we investigated changes in masseter muscle spindle function under an increased OVD (iOVD) condition. Responses of primary and secondary endings of masseter muscle spindles to cyclic sinusoidal stretches were investigated. Twenty barbiturate-anesthetized female Wistar rats were divided into control and iOVD groups. Rats in the iOVD group received a 2.0-mm composite resin build-up to the maxillary molars. After iOVD, masseter muscle spindle sensitivity gradually decreased. Primary and secondary spindle endings were affected differently. We conclude that iOVD caused reduction in masseter muscle spindle sensitivity. This result suggests that peripheral sensory plasticity may occur following changes in OVD. Such changes may provide a basis for physiological adaptation to clinical occlusal adjustments.

Acrylic Resins↗

PubMed2001

Molecular physiology of oxygen-sensitive potassium channels.

Physiological adaptation to acute hypoxia involves oxygen-sensing by a variety of specialized cells including carotid body type I cells, pulmonary neuroepithelial body cells, pulmonary artery myocytes and foetal adrenomedullary chromaffin cells. Hypoxia induces depolarization by closing a specific set of potassium channels and triggers cellular responses. Molecular biology strategies have recently allowed the identification of the K+ channel subunits expressed in these specialized cells. Several voltage-gated K+ channel subunits comprising six transmembrane segments and a single pore domain (Kv1.2, Kv1.5, Kv2.1, Kv3.1, Kv3.3, Kv4.2 and Kv9.3) are reversibly blocked by hypoxia when expressed in heterologous expression systems. Additionally, the background K+ channel subunit TASK-1, which comprises four transmembrane segments and two pore domains, is also involved in both oxygen- and acid-sensing in peripheral chemoreceptors. Progress is currently being made to identify the oxygen sensors. Regulatory beta subunits may play an important role in the modulation of Kv channel subunits by oxygen.

Adaptation, Physiological↗

PubMed2001

Implications of post-pneumonectomy compensatory lung growth in pulmonary physiology and disease.

In a number of species, partial pneumonectomy initiates hormonally regulated compensatory growth of the remaining lung lobes that restores normal mass, structure and function. Compensation is qualitatively similar across species, but differs with gender, age and hormonal status. Although the biology of response is best characterized in rats, dogs have proven valuable in defining post-operative physiological adaptations. Most recently, mice were recognized to offer unique opportunities to explore the genetic basis of the response, as well as to evaluate associated detrimental effects of pathophysiological significance in animals exposed to carcinogens. The pneumonectomy model thus offers powerful insight concerning adaptive organ growth.

Adaptation, Physiological↗

PubMed2005

Positive emotions: exploring the other hemisphere in behavioral medicine.

The search for the psychological antecedents of medical disorders has focused on the role of stress and negative emotional states. Previous research in this area has investigated relations between negative emotions and physiological adaptations (e.g., blood pressure elevations), adverse health behaviors (e.g., smoking), and social conditions (e.g., social isolation). In this discussion, we argue that more attention is needed to understand the effects of positive emotional states on health enhancement and disease prevention. In each of the areas cited previously, evidence is beginning to emerge that indicates that positive emotions can be associated with health promoting conditions. Interventions using cognitive behavioral strategies or meditation can increase positive emotional states that are maintained over time and that may benefit health and well-being. Implications for behavioral medicine are discussed.

Adaptation, Physiological↗

PubMed2005

Cortisol response in relation to the severity of stress and illness.

BACKGROUND: The aim of the study was to compare the adrenal response, the course of the ACTH/cortisol ratio, as well as the variance and the diagnostic performance of different cutoffs after 1 and 250 microg ACTH stimulation in different stress situations. METHODS: We investigated three groups with increasing stress levels: ambulatory controls (group A; n = 20), hospitalized medical patients (group B; n = 25), and patients undergoing coronary artery bypass grafting (group C; n = 29). All subjects underwent four consecutive ACTH stimulation tests and were randomized to either a 1- or 250-microg dose. RESULTS: Stimulated cortisol levels in group A were similar to basal cortisol levels under maximal stress (C3; P = 0.8). Peak cortisol concentrations were higher after 250 microg compared with 1 microg ACTH in group B (P = 0.006) and under maximal stress after extubation (group C3; P = 0.027), whereas there were no differences in group A. The ACTH/cortisol ratio was lower in surgical patients after extubation compared with unstressed conditions (P < or = 0.03) The within-subject variance was similar in ambulatory controls and medical patients and after both ACTH doses (all 17-36% of total variance). Cutoff dependent, the diagnosis of relative adrenal insufficiency would have been made in 0-58.3%, respectively. CONCLUSION: In moderate and major stress situations, cortisol concentrations in patients without hypothalamic-pituitary-adrenal disease were higher after stimulation with 250 microg compared with 1 mug ACTH. Data from our study give insight into the physiological adaptations of the hypothalamic-pituitary-adrenal axis to stress.

Adaptation, Physiological↗

PubMed1998

Effects of aerobic training in patients with mitochondrial myopathies.

We studied the physiologic adaptation of patients with mitochondrial myopathies to aerobic training. Ten patients underwent individually supervised, moderate-intensity aerobic training on a treadmill for 8 weeks. Biochemical and functional measures improved with training. Estimated aerobic capacity increased by 30%. Blood lactate concentrations at rest and after exercise decreased by 30%. Muscle phosphorus magnetic resonance spectroscopy measurements of adenosine diphosphate recovery after exercise improved by more than 60%. Fatigue and tolerance to daily activities also improved. Although the improvement in exercise tolerance may be due in part to reversal of the effects of secondary deconditioning, this uncontrolled clinical trial suggests that aerobic training can benefit patients with mitochondrial myopathies.

Activities of Daily Living↗

PubMed2003

Postnatal suppression of myomesin, muscle creatine kinase and the M-line in rat extraocular muscle.

The M-line and its associated creatine kinase (CK) M-isoform (CK-M) are ubiquitous features of skeletal and cardiac muscle. The M-line maintains myosin myofilaments in register, links the contractile apparatus to the cytoskeleton for external force transfer and localizes CK-based energy storage and transfer to the site of highest ATP demand. We establish here that the muscle group responsible for movements of the eye, extraocular muscle (EOM), is divergent from other striated muscles in lacking both an M-line and its associated CK-M. Although an M-line forms during myogenesis, both in vivo and in vitro, it is actively repressed after birth. Transcripts of the major M-line structural proteins, myomesin 1 and myomesin 2, follow the same pattern of postnatal downregulation, while the embryonic heart-specific EH-myomesin 1 transcript is expressed early and retained in adult eye muscle. By immunocytochemistry, myomesin protein is absent from adult EOM sarcomeres. M-line suppression does not occur in organotypic co-culture with oculomotor motoneurons, suggesting that the mechanism for suppression may lie in muscle group-specific activation or workload patterns experienced only in vivo. The M-line is, however, still lost in dark-reared rats, despite the developmental delay this paradigm produces in the visuomotor system and EOMs. EOM was low in all CK isoform transcripts except for the sarcomeric mitochondrial (Ckmt2) isoform. Total CK enzyme activity of EOM was one-third that of hindlimb muscle. These findings are singularly unique among fast-twitch skeletal muscles. Since EOM exhibits isoform diversity for other sarcomeric proteins, the M-line/CK-M divergence probably represents a key physiological adaptation for the unique energetics and functional demands placed on this muscle group in voluntary and reflexive eye movements.

Adaptation, Physiological↗

PubMed2006

Post-genomic approaches to understanding the mechanisms of environmentally induced phenotypic plasticity.

Post-genomic techniques offer new and detailed insights into the mechanisms underpinning all biological processes, including phenotypic plasticity and environmentally relevant phenotypes. Although they require access to genomic resources it is now possible to create these for species of comparative or environmental interest even within a modest research project. Here we describe an open transcript screen for genes responding to environmental cold that might account for the acquired cold-specific phenotype in all its complex manifestations. Construction of a cDNA microarray led to a survey of transcript expression levels in seven tissues of carp, as a function of time, and three different extents of cooling. The resulting data delineated a common stress response found in all tissues that comprises genes involved in cellular homeostasis, including energy charge, ATP turnover, protein turnover and stress protein production. These genes respond to kinds of perturbation other than cold and probably form part of a more general stress response common to other species. We also defined tissue-specific response patterns of transcript regulation whose main characteristics were investigated by a profiling technique based on categorisation of gene function. These genes underpin the highly tissue-specific pattern of physiological adaptations observed in the cold-acclimated fish. As a result we have identified a large number of candidate gene targets with which to investigate adaptive responses to environmental challenge.

Adaptation, Physiological↗