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PubMed2006

Vital functions of corticotropin-releasing factor (CRF) pathways in maintenance and regulation of energy homeostasis.

Regulation of energy homeostasis is a vital function of the CNS requiring adaptive responses to maintain and support life after stress perturbations. The mechanisms whereby these processes occur are, however, only partially understood. A major determinate of these responses is corticotropin-releasing factor (CRF). Receptors for CRF, CRFR1 and CRFR2, have been hypothesized to play distinct roles in the alterations necessary for homeostatic maintenance. The function of CRFR2, in particular, has remained elusive despite its presence in both the CNS and periphery. In this work, we have used complimentary gene deletion and pharmacological approaches to elucidate the crucial role CRFR2 plays in the regulation of regional tissue thermogenesis and adaptive physiology. Analyses of interscapular brown adipose tissue (IBAT) thermogenesis by thermal signature analysis and the concordant biochemical changes in key sympathetic components in mice deficient for CRFR2 revealed significantly elevated basal IBAT thermogenesis and prolonged adrenergic responsivity of IBAT in older mice. Measurement of metabolic rates by indirect calorimetry after chronic high-fat diet challenge and treatment with the CRFR1 antagonist NBI-27914 revealed a decreased respiratory exchange ratio of these mice that was normalized with NBI-27914. Further, as a definitive measure for physiological pathology, mice examined in a behavioral model of differential temperature selection showed a predilection for warmer external temperatures, supporting a loss of body heat in these mice. These studies provide physiological, biochemical, and behavioral evidence for the critical participation of CRF pathways in the maintenance and adaptive responses necessary for regulation of energy homeostasis.

Adipose Tissue, Brown↗
PubMed1989

Beyond the thrifty gene: metabolic implications of prehistoric migration into the New World.

Several models have been proposed to explain the high prevalence of non-insulin dependent diabetes mellitus (NIDDM) and other diseases among New World populations. This paper examines the implications of a northern hunting adaptation (reliance on animal foods, seasonal shortages) in terms of energy digestion, absorption, metabolism and storage. Physiologic adaptations to a high protein, moderate fat, low carbohydrate diet are then examined in the context of agriculturally-based subsistence systems and in industrialized societies. Specific metabolic pathways, consistent with the work of both Neel and Weiss, are identified as fruitful areas for further research regarding genetic variants in New World populations.

Diabetes Mellitus, Type 2↗
PubMedDate not supplied

[Phosphoric stress and antioxidative power of wheat roots].

The change of antioxydative power of metabolites in the wheat root system (cv Polesskaya 90 and cv Polesskaya 92) under effect of stress doses of phosphoric nutrition (4-fold dose and phosphoric deficit in nutrient mixture of water culture) proves that phosphoric stress causes peroxidation of membrane lipids. These changes are a nonspecific reaction of membranes in root epithelial cells. Stress and responsive changes in the membrane system are recorded by an antioxydative power decreasing root metabolites. This is the first stage of plant biochemical adaptation (7 to 14 days of growth). The second stage (21 to 28 days of growth) is characterised by the increasing of antioxydative power. However, nonspecific character of the primary reaction of membrane system in root cells at high doses and phosphoric deficite in nutrient mixture changes into clear specific reaction at physiological adaptation level. This is revealed in the change of growth function and kinetics of phosphoric accumulation. Phosphoric deficiency at critical phosphoric concentration in plant roots (0.2% P2O5 of dry mass) results in the increase of growth processes. This is revealed in accumulation of root biomass. At high phosphoric concentrations (1.04% P2O3) the development of root system is inactivated and phosphoric absorption is decreased. The similar specificity in the changes of growth and absorption function of root system is considered to be adapting. The changes of antioxydative power and hence the destroying apparatus in epithelial cells of root system advance the damage at physiological and morphological level and can define wheat adaptation ability to extreme conditions of phosphoric nutrition.

Adaptation, Biological↗
PubMed2005

Physiological and metabolic adaptations of Potamogeton pectinatus L. tubers support rapid elongation of stem tissue in the absence of oxygen.

Tubers of Potamogeton pectinatus L., an aquatic pondweed, over-winter in the anoxic sediments of rivers, lakes and marshes. Growth of the pre-formed shoot that emerges from the tuber is remarkably tolerant to anoxia, with elongation of the stem occurring faster when oxygen is absent. This response, which allows the shoot to reach oxygenated waters, occurs despite a 69-81% reduction in the rate of ATP production, and it is underpinned by several physiological and metabolic adaptations that contribute to efficient energy usage. First, extension of the pre-formed shoot is the result of cell expansion, without the accumulation of new cellular material. Secondly, after over-wintering, the tuber and pre-formed shoot have the enzymes necessary for a rapid fermentative response at the onset of growth under anoxia. Thirdly, the incorporation of [(35)S]methionine into protein is greatly reduced under anoxia. The majority of the anoxically synthesized proteins differ from those in aerobically grown tissue, implying an extensive redirection of protein synthesis under anoxia. Finally, anoxia-induced cytoplasmic acidosis is prevented to an unprecedented degree. The adaptations of this anoxia-tolerant plant tissue emphasize the importance of the mechanisms that balance ATP production and consumption in the absence of oxygen.

Adaptation, Physiological↗
PubMed2001

In Situ Assessment on the Physiological State of Purple and Green Sulfur Bacteria through the Analyses of Pigment and 5S rRNA Content.

Time-depth distribution of the microbial anaerobic assemblage of Lake Cisó was analyzed by microscopy, pigment composition, and electrophoretic analysis of 5S rRNAs. Purple (Amoebobacter-like and Thiocystis minor-like cells) and green (Chlorobium-like) sulfur bacteria were very abundant. Both groups coexisted in depth and in time despite the fact that they compete for the same natural resources (e.g., light and sulfide). Cell abundance, group-specific pigment content, and group-specific 5S rRNA content did not change in parallel with depth. This was due to variations in the specific content of both RNA and pigments. Specific content of RNA was systematically higher in purple than in green sulfur bacteria. The latter, in turn, displayed a much higher pigment content. Specific content of both RNA and pigments changed with depth and time. Analysis of tRNA band patterns indicated no changes in the populations forming the assemblage. Changes in specific contents, therefore, were the result of physiological adaptations of the populations already present in the system. We concluded that each group of bacteria showed differential adaptations in both RNA and pigment content, and that the specific contents measured were good indicators of the physiological status of these bacteria in situ. The higher content of RNA in purple sulfur bacteria indicates that these organisms are the main contributors to anaerobic carbon fixation and sulfide oxidation processes in Lake Cisó.

Journal Article↗
PubMed2003

The complex oxidative stress response of Bacteroides fragilis: the role of OxyR in control of gene expression.

Gram-negative anaerobes in the genus Bacteroides are the predominant members of the GI-tract microflora where they play an important role in normal intestinal physiology. Bacteroides spp. also are significant opportunistic pathogens responsible for an array of intra-abdominal and other infections. Bacteroides fragilis is the most common anaerobic pathogen and it possesses virulence factors such as a capsule and neuraminidase that contribute to its success as a pathogen. Infection occurs when organisms escape from the anaerobic colon to aerobic sites such as the peritoneum where O(2) concentrations average 6%. Thus in addition to the classic virulence factors, resistance to oxidative stress is essential and may be involved in the initiation and persistence of infection. In fact, B. fragilis is highly O(2) tolerant, surviving extended periods (>24h) of O(2) exposure without a significant affect on viability. For protection against this oxidative stress B. fragilis mounts a complex physiological response that includes induction of >28 proteins involved in detoxification of oxygen radicals, protection of macromolecules, and adaptive physiology. One experimental strategy used to characterize this oxidative stress response is the direct detection of genes and proteins induced during exposure to O(2) or H(2)O(2). The methods employed have included RNA differential display to capture unique mRNA transcripts produced during oxidative stress, and native or 2D-gel electrophoresis to isolate and identify newly formed stress-induced proteins. Using these and other approaches a wide array of genes induced by oxidative stress have been discovered. These include genes for catalase, superoxide dismutase, thioredoxin-peroxidase, p20-peroxidase, cytochrome c peroxidase, Dps, alkyl hydroperoxidase, aerobic ribonucleotide reductase, ruberythrin, starch utilization, aspartate decarboxylase, and an RNA binding protein. The genes encoding these activities fall into three regulatory classes: (1) induced by O(2) only, (2) induced by H(2)O(2) only, and (3) induced by either O(2) or H(2)O(2). Such a complex regulatory response will likely involve multiple regulators. Thus far one regulator has been identified, OxyR, which controls a subset of the class 3 genes that are induced by either O(2) or H(2)O(2). OxyR responds rapidly to oxidative stress and transcriptional analyses have shown that OxyR-controlled genes are activated by as little as 0.5% O(2) or 10 microM H(2)O(2). Maximal expression of most OxyR regulon genes was reached at 50 microM H(2)O(2) and 2% O(2). These oxidant concentrations are similar to environmental levels that would be experienced by the organisms in tissues outside of the colon suggesting that the OxyR regulon would be induced during the course of an infection.

Journal Article↗
PubMed2004

High versus low intensity exercise training in pulmonary rehabilitation: is more better?

BACKGROUND: Exercise training is considered a necessary component of comprehensive pulmonary rehabilitation. However, to date, there is no consensus on an exercise training strategy for pulmonary rehabilitation, and this has resulted in varied approaches to this intervention in its literature. As in healthy individuals, the effect of exercise training on patients with chronic lung disease is dose dependent, with higher intensities resulting in greater physiological adaptations than lower intensities. RESULTS: It is not clear from our review of the literature that these enhanced physiological effects from higher levels of exercise training translate into a reduced burden of symptoms, hence a better quality of life. Indeed, there is some evidence that pulmonary rehabilitation approaches incorporating lower intensities of exercise training are at least as good in improving questionnaire rated symptoms of health status. This provides food for thought, since the prominent goal of pulmonary rehabilitation should be to reduce bothersome symptoms or enhance health status, not simply increase endurance time on a cycle ergometer.

Exercise Therapy↗
PubMed2005

Intracranial pressure dynamics assessed by noninvasive ultrasound during 30 days of bed rest.

INTRODUCTION: Intracranial pressure (ICP) may be an important contributor to symptoms of space adaptation syndrome during the initial days of microgravity exposure. The temporary nature of these symptoms suggests that some physiologic adaptation or compensation occurs. Fluid shifts similar to those in microgravity can be simulated on Earth using head-down tilt (HDT) bed rest. This study was performed to calibrate a new noninvasive ICP instrument and to investigate ICP adaptation during 30 d of HDT bed rest. METHODS: A noninvasive ultrasound technique that measures small skull expansions with fluctuations in ICP was used to measure cranial oscillations before and near the end of 30-d HDT bed rest in eight healthy, male volunteers. Pulse phase-locked loop (PPLL) output voltage and arterial BP were continuously monitored and correlated. RESULTS: The amplitude of intracranial distance pulsation decreased during 30-d bed rest. Prior to bed rest, the PPLL amplitude was 25 +/- 9 mV and this amplitude was reduced by 60% to 9 +/- 4 mV (a value consistent with that of upright posture) at the end of HDT bed rest (p = 0.01). DISCUSSION: PPLL measurements of skull pulsations are acutely posture dependent, being significantly higher in supine and HDT as compared with upright posture. A cephalad fluid shift is probably the responsible mechanism. Our results indicate that there are adaptations to intracranial pooling of blood and tissue fluid during bed rest that reduce skull pulsation amplitudes to values similar to those obtained in normal upright posture. Detailed studies of the time course of cranial vessel and bone adaptations may provide insights into the potential adaptative mechanisms.

Aerospace Medicine↗
PubMedDate not supplied

Coping and adaptation in children with diabetes.

The purpose of this study was to investigate the influence of age, coping behavior, and self-care on psychological, social, and physiologic adaptation in preadolescents and adolescents with diabetes. Children (N = 103) with insulin-dependent diabetes mellitus (IDDM) between 8 and 18 years of age and their parents participated in the study. Findings indicated that preadolescent children were significantly less depressed, less anxious, coped in more positive ways, had fewer adjustment problems, and were in better metabolic control than their adolescent counterparts. Age and secondary sexual development were related to psychosocial adaptation and metabolic control of the diabetes. Further, those who coped by avoiding their problems and who were more depressed were the most likely to have problems in both adjustment and metabolic control with 56% of the variance in metabolic control explained by the variables studied. These findings indicate that preadolescents and adolescents cope differently with a chronic illness, and that interventions should be designed to identify and help those with inappropriate coping styles.

Adaptation, Psychological↗
PubMed1997

Acute adaptive changes in food intake pattern following olfactory ablation in rats.

We determined whether acute compensatory feeding pattern changes after bulbectomy persist on a chronic basis, or whether physiological adaptation occurs to normalize acute changes. Rats were randomized to olfactory bulbectomy or sham operation; all had jugular vein catheterization. Food intake, meal number and size were studied during infusion of parenteral nutrients providing 100% daily caloric intake (PN-100) to minimize post-ingestive effects. Rats were randomly assigned to acute (from day 14 after operation, PN-100 infused for 4 days, followed by 4 days of saline infusion) or chronic study (PN-100 infused for 4 days from day 40, followed by 4 days of saline infusion). After olfactory ablation, acutely decreased meal size was offset by increased meal number, but 40 days after, baseline differences between meal size and number no longer existed. No qualitative differences in response to PN-100 were noted between acute and chronic groups. Findings suggest a functional adaptation of food intake regulatory mechanism between 14 and 40 days after bulbectomy.

Adaptation, Psychological↗
PubMed2006

Adaptations to fasting in a terrestrial mustelid, the sable (Martes zibellina).

The aim of this study was to investigate whether the actively wintering Palearctic sable Martes zibellina has evolved physiological adaptations to tolerate nutritional scarcity. Sixteen farm-bred male sables were divided into a fed control group and an experimental group fasted for 4 days. The rate of weight loss in the sable was similar to other medium-sized mustelids. Fasting led to hypoglycaemia and to a decreased lymphocyte percentage. The sable derived metabolic energy from both subcutaneous and intraabdominal white adipose tissues and the relative decrease in fat mass was the largest for the retroperitoneal and subcutaneous depots. Metabolic energy derived partly from body proteins indicated by the increased plasma levels of urea, uric acid and total essential amino acids. Triacylglycerols accumulated in the livers of the fasted sables and the increased plasma aminotransferase activities suggested hepatic dysfunction. The decreased plasma insulin concentrations and the elevated cortisol levels probably contributed to stimulated lipolysis and protein catabolism. Moreover, fasting increased the plasma ghrelin concentrations of the sables and down-regulated the thyroid activity.

Acclimatization↗
PubMed1999

Multiple immediate-early gene expression during physiological and endocrine adaptation to repeated stress.

This study had three objectives: (i) to determine whether there were individual differences in the activation and adaptation of a range of immediate-early genes to repeated restraint stress, (ii) to monitor physiological responses (endocrine, cardiovascular and core temperature) and their adaptation with repeated presentations of the stressor, and (iii) to determine whether any of these indices were altered by dehydroepiandrosterone, an anti-glucocorticoid steroid known to be reduced in humans by stress. Four groups of male rats were implanted subcutaneously with either dehydroepiandrosterone or control (paraffin) pellets. They were then subjected to either a single or 14 days of restraint (60 min/day) or transferred to the testing room (unstressed). Repeatedly stressed animals and their controls were also implanted with intra-abdominal telemetric transmitters to record heart rate and core temperature. Protein products for c-fos,fos-b, c-jun and jun-b were displayed by immunocytochemistry. Areas examined included the ventrolateral septum, hypothalamic paraventricular nucleus, amygdala, locus coeruleus and nucleus of the solitary tract. Acute restraint increased Fos immunoreactivity in all of the areas examined, with the exception of the medial amygdala. The pattern of induction for Fos-B and Jun-B was similar, while c-Jun was only increased in the septum (though constitutive levels were high in most structures compared to the other proteins examined). After 14 days of restraint, immediate-early gene immunostaining was reduced in all of the areas examined, though the extent of adaptation depended on the area and immediate-early gene. In the forebrain, Fos expression adapted in the paraventricular nucleus, amygdala and septum, whereas Fos-B and c-Jun adapted incompletely in the septum. In contrast, Jun-B behaved like Fos. In the brainstem, Fos, Fos-B and Jun-B expression adapted in the nucleus of the solitary tract (but not the locus coeruleus). Corticosterone levels were still raised above baseline, but the response was blunted compared to acute stress. There was marked stress-induced hypothermia which did not adapt during the restraint session, but this returned to baseline during restraint after about five days. In contrast, stress-induced tachycardia did not change during repeated restraint. Dehydroepiandrosterone implants had no clear-cut effects on any immunostaining following acute stress, though there was a trend towards lessened adaptation of the Fos response in the septum after steroid treatment. Dehydroepiandrosterone also did not affect the cardiovascular or endocrine responses to repeated restraint. These experiments show that adaptation of the expression of multiple immediate-early genes occurs during repeated restraint, but in a site-specific pattern in the brains of male rats.

Adaptation, Physiological↗
PubMed2004

Experimental models of stress and wound healing.

Experimental animal models have been used to examine stress-induced interactions among the nervous, endocrine, and immune systems. Generally, the response to stress results in a body-wide set of physiologic adaptations, mediated through the activation of neuroendocrine pathways that intersect and modulate inflammatory and immune responses. These interacting responses modulate diverse physiological processes including the initiation of tissue repair and wound healing. Two different stressors were used to activate neuroendocrine responses to study their impact on wound healing: restraint (RST) and social disruption (SDR). Previous studies showed that both stressors activate the hypothalamic-pituitary-adrenal (HPA) axis, resulting in elevated plasma levels of the corticosterone (cort) response and modulation of pro-inflammatory cytokine response. To test the effects of stress-induced HPA activation on inflammatory responses and wound healing, a 3.5-mm cutaneous punch biopsy wound was placed on the dorsal surface of control and stressed (RST or SDR) C57BL/6 male mice and the kinetics of wound healing were studied over 10 days. RST slowed wound healing in inbred C57BL/6 mice, whereas the wounds on SDR mice healed in a fashion similar to the non-stressed, home cage controls.

Analysis of Variance↗