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1.
Int J Psychophysiol ; 98(1): 95-111, 2015 Oct.
Article in English | MEDLINE | ID: mdl-26166440

ABSTRACT

Whilst a number of previous studies have been conducted in order to investigate functional brain changes associated with eyes-closed meditation techniques, there is a relative scarcity in the literature with regards to changes occurring during eyes-open meditation. The current project used magnetoencephalography (MEG) to investigate differences in spectral power and functional connectivity between 11 long-term mindfulness meditators (LTMMs) with >5 years of experience and 12 meditation-naïve control participants both during baseline eyes-open rest and eyes-open open-monitoring (OM) mindfulness meditation. During resting with eyes-open, prior to meditating, greater mean alpha power was observed for LTMMs in comparison to controls. However, during the course of OM meditation, a significantly greater increase in theta power was observed over a broad fronto-centro-parietal region for control participants in comparison to LTMMs. In contrast, whole-head mean connectivity was found to be significantly greater for long-term meditators in comparison to controls in the theta band both during rest as well as during meditation. Additionally, mean connectivity was significantly lower for long-term meditators in the low gamma band during rest and significantly lower in both low and high gamma bands during meditation; and the variance of low-gamma connectivity scores for long-term meditators was significantly decreased compared to the control group. The current study provides important new information as to the trait functional changes in brain activity associated with long-term mindfulness meditation, as well as the state changes specifically associated with eyes-open open monitoring meditation techniques.


Subject(s)
Brain Mapping , Brain Waves/physiology , Brain/physiology , Mindfulness/methods , Anxiety/physiopathology , Anxiety/rehabilitation , Cluster Analysis , Electroencephalography , Eye , Female , Fourier Analysis , Humans , Longitudinal Studies , Magnetoencephalography , Male , Middle Aged , Rest , Surveys and Questionnaires
2.
Nitric Oxide ; 32: 1-12, 2013 Aug 01.
Article in English | MEDLINE | ID: mdl-23545405

ABSTRACT

African lungfishes (Protopterus spp.) are obligate air breathers which enter in a prolonged torpor (aestivation) in association with metabolic depression, and biochemical and morpho-functional readjustments during the dry season. During aestivation, the lungfish heart continues to pump, while the skeletal muscle stops to function but can immediately contract during arousal. Currently, nothing is known regarding the orchestration of the multilevel rearrangements occurring in myotomal and myocardial muscles during aestivation and arousal. Because of its universal role in cardio-circulatory and muscle homeostasis, nitric oxide (NO) could be involved in coordinating these stress-induced adaptations. Western blotting and immunofluorescence microscopy on cardiac and skeletal muscles of Protopterus annectens (freshwater, 6months of aestivation and 6days after arousal) showed that expression, localization and activity of the endothelial-like nitric oxide synthase (eNOS) isoform and its partners Akt and Hsp-90 are tissue-specifically modulated. During aestivation, phospho-eNOS/eNOS and phospho-Akt/Akt ratios increased in the heart but decreased in the skeletal muscle. By contrast, Hsp-90 increased in both muscle types during aestivation. TUNEL assay revealed that increased apoptosis occurred in the skeletal muscle of aestivating lungfish, but the myocardial apoptotic rate of the aestivating lungfish remained unchanged as compared with the freshwater control. Consistent with the preserved cardiac activity during aestivation, the expression of apoptosis repressor (ARC) also remained unchanged in the heart of aestivating and aroused fish as compared with the freshwater control. Contrarily, ARC expression was strongly reduced in the skeletal muscle of aestivating lungfish. On the whole, our data indicate that changes in the eNOS/NO system and cell turnover are implicated in the morpho-functional readjustments occurring in lungfish cardiac and skeletal muscle during the switch from freshwater to aestivation, and between the maintenance and arousal phases of aestivation.


Subject(s)
Apoptosis Regulatory Proteins/metabolism , Fishes/metabolism , Muscle, Skeletal/enzymology , Myocardium/enzymology , Nitric Oxide Synthase Type III/metabolism , Animals , Apoptosis/physiology , Estivation , Fresh Water , HSP90 Heat-Shock Proteins/metabolism , Muscle Proteins/metabolism , Muscle, Skeletal/cytology , Muscle, Skeletal/metabolism , Myocardium/cytology , Myocardium/metabolism , Proto-Oncogene Proteins c-akt/metabolism
3.
Physiotherapy ; 99(1): 1-11, 2013 Mar.
Article in English | MEDLINE | ID: mdl-23219634

ABSTRACT

BACKGROUND: Anorexia nervosa is an eating disorder that is often preceded by excessive physical activity. As such, exercise is not often prescribed in the clinical management of individuals with anorexia nervosa. OBJECTIVE: To examine the effects of supervised exercise training in patients with anorexia nervosa. DATA SOURCES: Five databases were searched from their inception to Week 14 of 2011 using the subject headings 'anorexia' and 'exercise' to identify relevant studies. ELIGIBILITY CRITERIA: PRISMA guidelines were followed. Studies that investigated the effects of inclusion of supervised exercise training in clinical management with usual management in patients diagnosed with anorexia nervosa were included in this review. Case reports were excluded. DATA EXTRACTION AND SYNTHESIS: Two reviewers independently extracted data using a standardised assessment form. Quality assessment was rated for the controlled trials and single-group studies using the PEDro scale and Downs and Black scale, respectively. Fixed or random effect approaches were used to determine effect size, depending on the heterogeneity of the studies. RESULTS: Pooled randomised controlled trials and quasi-randomised studies showed no significant effect of supervised exercise training on selected anthropometric measurements, while the single-group studies showed significant improvement in weight and body fat. Although Short Form-36 revealed no training effect, distorted feelings about food and exercise were reduced. Cardiovascular fitness also improved with no decrease in weight. LIMITATIONS: Heterogeneity of exercise training programmes, small sample size (n≤20) for 67% of the trials, and inability to exclude publication bias. CONCLUSIONS: Inclusion of supervised exercise training in the comprehensive management of patients with anorexia nervosa appears to be safe, as no detrimental effect was observed in anthropometry. Strength and cardiovascular fitness were also shown to improve.


Subject(s)
Anorexia Nervosa/rehabilitation , Exercise Therapy/methods , Anthropometry , Humans
4.
J Comp Physiol B ; 182(2): 231-45, 2012 Feb.
Article in English | MEDLINE | ID: mdl-21915614

ABSTRACT

This study aimed to identify estivation-specific gene clusters through the determination of differential gene expressions in the liver of Protopterus annectens after 6 days of estivation in a mucus cocoon in air (normoxia) using suppression subtractive hybridization polymerase chain reaction. Our results demonstrated that 6 days of estivation in normoxia led to up-regulation of mRNA expressions of several genes related to urea synthesis, including carbamoyl phosphate synthetase (Cps), argininosuccinate synthetase and glutamine synthetase. They indicate that increased urea synthesis, despite being energy-intensive, is an important adaptive response of estivation. They also offer indirect support to the proposition that urea synthesis in this lungfish involved a Cps that uses glutamine as a substrate. In addition, up- or down-regulation of several gene clusters occurred in the liver of P. annectens after 6 days of estivation in normoxia. These estivation-specific genes were involved in the prevention of clot formation, activation of the lectin pathway for complement activation, conservation of minerals (e.g. iron and copper) and increased production of hemoglobin beta. Since there were up- and down-regulation of mRNA expressions of genes related to ribosomal proteins and translational elongation factors, there could be simultaneous increases in protein degradation and protein synthesis during the first 6 days (the induction phase) of estivation, confirming the importance of reconstruction of protein structures in preparation for the maintenance phase of estivation.


Subject(s)
Estivation/physiology , Fishes/metabolism , Fishes/physiology , Gene Expression Regulation/physiology , Liver/metabolism , Animals , Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor/metabolism , DNA Primers/genetics , Fishes/genetics , Gene Expression Profiling , Gene Library , Real-Time Polymerase Chain Reaction , Urea/metabolism
5.
J Comp Physiol B ; 182(3): 367-79, 2012 Apr.
Article in English | MEDLINE | ID: mdl-22038021

ABSTRACT

This study aimed to obtain the full sequence of carbamoyl phosphate synthetase III (cps III) from, and to determine the mRNA expression of cps III in, the liver of P. annectens during aestivation in air, hypoxia or mud, or exposure to environmental ammonia (100 mmol l(-1) NH(4)Cl). The complete coding cDNA sequence of cps III from the liver of P. annectens consisted of 4530 bp, which coded for 1,510 amino acids with an estimated molecular mass of 166.1 kDa. The Cps III of P. annectens consisted of a mitochondrial targeting sequence of 44 amino acid residues, a GAT domain spanning from tyrosine 45 to isoleucine 414, and a methylglyoxal synthase-like domain spanning from valine 433 to arginine 1513. Two cysteine residues (cysteine 1337 and cysteine 1347) that are characteristic of N-acetylglutamate dependency were also present. The critical Cys-His-Glu catalytic triad (cysteine 301, histidine 385 and glutamate 387) together with methionine 302 and glutamine 305 affirmed that P. annectens expressed Cps III and not Cps I. A comparison of the translated amino acid sequence of Cps III from P. annectens with CPS sequences from other animals revealed that it shared the highest similarity with elasmobranch Cps III. A phylogenetic analysis indicates that P. annectens CPS III could have evolved from Cps III of elasmobranchs. Indeed, Cps III from P. annectens used mainly glutamine as the substrate, and its activity decreased significantly when glutamine and ammonia were included together in the assay system. There were significant increases (9- to 12-fold) in the mRNA expression of cps III in the liver of fish during the induction phase (days 3 and 6) of aestivation in air. Aestivation in hypoxia or in mud had a delayed effect on the increase in the mRNA expression of cps III, which extended beyond the induction phase of aestivation, reiterating the importance of differentiating effects that are intrinsic to aestivation from those intrinsic to hypoxia. Furthermore, results from this study confirmed that environmental ammonia exposure led to a significant increase in the mRNA expression of cps III in the liver of P. annectens, alluding to the important functional role of urea not only as a product of ammonia detoxification but also as a putative internal cue for aestivation.


Subject(s)
Carbon-Nitrogen Ligases/genetics , Carbon-Nitrogen Ligases/metabolism , Estivation/physiology , Evolution, Molecular , Fishes/physiology , Gene Expression Regulation/physiology , Phylogeny , Amino Acid Sequence , Ammonia/toxicity , Animals , Base Sequence , DNA, Complementary/genetics , Estivation/genetics , Fishes/genetics , Gene Expression Regulation/drug effects , Liver/metabolism , Molecular Sequence Data , RNA, Messenger/metabolism , Sequence Analysis, DNA , Species Specificity
6.
Singapore Med J ; 51(6): 518-21; quiz 522, 2010 Jun.
Article in English | MEDLINE | ID: mdl-20658114

ABSTRACT

The Health Promotion Board (HPB) and the Ministry of Health (MOH) publish clinical practice guidelines to provide doctors and patients in Singapore with evidence-based guidance on managing important medical conditions. This article reproduces the introduction and executive summary (with recommendations from the guidelines) from the HPB-MOH clinical practice guidelines on Functional Screening for Older Adults in the Community, for the information of readers of the Singapore Medical Journal. Chapters and page numbers mentioned in the reproduced extract refer to the full text of the guidelines, which are available from the Health Promotion Board website (http://www.hpb.gov.sg/uploadedFiles/HPB_Online/Publications/CPGFunctionalscreening.pdf). The recommendations should be used with reference to the full text of the guidelines. Following this article are multiple choice questions based on the full text of the guidelines.


Subject(s)
Geriatrics/methods , Health Promotion/methods , Aged , Aging , Community Health Services/organization & administration , Evidence-Based Medicine , Geriatrics/standards , Guidelines as Topic , Health Promotion/standards , Humans , Mass Screening/methods , Singapore
7.
J Exp Biol ; 212(Pt 23): 3828-36, 2009 Dec.
Article in English | MEDLINE | ID: mdl-19915125

ABSTRACT

This study aimed to examine whether the stenohaline freshwater stingray, Potamotrygon motoro, which lacks a functional ornithine-urea cycle, would up-regulate glutamine synthetase (GS) activity and protein abundance, and accumulate glutamine during a progressive transfer from freshwater to brackish (15 per thousand) water with daily feeding. Our results revealed that, similar to other freshwater teleosts, P. motoro performed hyperosmotic regulation, with very low urea concentrations in plasma and tissues, in freshwater. In 15 per thousand water, it was non-ureotelic and non-ureoosmotic, acting mainly as an osmoconformer with its plasma osmolality, [Na+] and [Cl-] comparable to those of the external medium. There were significant increases in the content of several free amino acids (FAAs), including glutamate, glutamine and glycine, in muscle and liver, but not in plasma, indicating that FAAs could contribute in part to cell volume regulation. Furthermore, exposure of P. motoro to 15 per thousand water led to up-regulation of GS activity and protein abundance in both liver and muscle. Thus, our results indicate for the first time that, despite the inability to synthesize urea and the lack of functional carbamoyl phosphate synthetase III (CPS III) which uses glutamine as a substrate, P. motoro retained the capacity to up-regulate the activity and protein expression of GS in response to salinity stress. Potamotrygon motoro was not nitrogen (N) limited when exposed to 15 per thousand water with feeding, and there were no significant changes in the amination and deamination activities of hepatic glutamate dehydrogenase. In contrast, P. motoro became N limited when exposed to 10 per thousand water with fasting and could not survive well in 15 per thousand water without food.


Subject(s)
Acclimatization/physiology , Gene Expression Regulation, Enzymologic/physiology , Glutamate-Ammonia Ligase/metabolism , Glutamine/metabolism , Salinity , Skates, Fish/physiology , Ammonia/metabolism , Analysis of Variance , Animals , Blotting, Western , Fresh Water/chemistry , Liver/metabolism , Muscle, Skeletal/metabolism , Skates, Fish/metabolism , Urea/metabolism
8.
J Dent Res ; 87(7): 692-6, 2008 Jul.
Article in English | MEDLINE | ID: mdl-18573993

ABSTRACT

During orthodontic tooth movement, bone resorption occurs at the compression site. However, the mechanism underlying resorption remains unclear. Applying compressive force to human osteoblast-like cells grown in a 3D collagen gel, we examined gene induction by using microarray and RT-PCR analysis. Among 43 genes exhibiting significant changes, cyclo-oxygenase-2, ornithine decarboxylase, and matrix metalloproteinase-3 (MMP-3) were up-regulated, whereas membrane-bound interleukin-1 receptor accessory protein was down-regulated. The MMP-3 protein increases were further confirmed by Western blot. To ascertain whether MMP-3 is up-regulated in vivo by orthodontic force, we examined human bone samples at the compressive site by realigning the angulated molars. Immunohistochemical staining revealed MMP-3 distributed along the compressive site of the bony region within 3 days of compression. Since MMP-3 participates in degradation of a wide range of extracellular matrix molecules, we propose that MMP-3 plays an important role in bone resorption during orthodontic tooth movement.


Subject(s)
Alveolar Process/enzymology , Bone Remodeling/physiology , Matrix Metalloproteinase 3/metabolism , Osteoblasts/enzymology , Tooth Movement Techniques , Adaptation, Physiological , Cell Culture Techniques , Cells, Cultured , Collagen , Cyclooxygenase 2/metabolism , Gels , Gene Expression Profiling , Gene Expression Regulation , Humans , Models, Biological , Oligonucleotide Array Sequence Analysis , Ornithine Decarboxylase/metabolism , Osteoblasts/cytology , Statistics, Nonparametric , Transcriptional Activation
9.
J Comp Physiol B ; 178(7): 853-65, 2008 Sep.
Article in English | MEDLINE | ID: mdl-18504593

ABSTRACT

We examined the energy status, nitrogen metabolism and hepatic glutamate dehydrogenase activity in the African lungfish Protopterus annectens during aestivation in normoxia (air) or hypoxia (2% O(2) in N(2)), with tissues sampled on day 3 (aerial exposure with preparation for aestivation), day 6 (entering into aestivation) or day 12 (undergoing aestivation). There was no accumulation of ammonia in tissues of fish exposed to normoxia or hypoxia throughout the 12-day period. Ammonia toxicity was avoided by increased urea synthesis and/or decreased endogenous N production (as ammonia), but the dependency on these two mechanisms differed between the normoxic and the hypoxic fish. The rate of urea synthesis increased 2.4-fold, with only a 12% decrease in the rate of N production in the normoxic fish. By contrast, the rate of N production in the hypoxic fish decreased by 58%, with no increase in the rate of urea synthesis. Using in vivo (31)P NMR spectroscopy, it was demonstrated that hypoxia led to significantly lower ATP concentration on day 12 and significantly lower creatine phosphate concentration on days 1, 6, 9 and 12 in the anterior region of the fish as compared with normoxia. Additionally, the hypoxic fish had lower creatine phosphate concentration in the middle region than the normoxic fish on day 9. Hence, lowering the dependency on increased urea synthesis to detoxify ammonia, which is energy intensive by reducing N production, would conserve cellular energy during aestivation in hypoxia. Indeed, there were significant increases in glutamate concentrations in tissues of fish aestivating in hypoxia, which indicates decreases in its degradation and/or transamination. Furthermore, there were significant increases in the hepatic glutamate dehydrogenase (GDH) amination activity, the amination/deamination ratio and the dependency of the amination activity on ADP activation in fish on days 6 and 12 in hypoxia, but similar changes occurred only in the normoxic fish on day 12. Therefore, our results indicate for the first time that P. annectens exhibited different adaptive responses during aestivation in normoxia and in hypoxia. They also indicate that reduction in nitrogen metabolism, and probably metabolic rate, did not occur simply in association with aestivation (in normoxia) but responded more effectively to a combined effect of aestivation and hypoxia.


Subject(s)
Energy Metabolism/physiology , Estivation/physiology , Fishes/metabolism , Hypoxia/physiopathology , Nitrogen/metabolism , Adenosine Triphosphate/metabolism , Ammonia/metabolism , Animals , Fatty Acids, Nonesterified/metabolism , Female , Glutamate Dehydrogenase/metabolism , Liver/metabolism , Male , Muscle, Skeletal/metabolism , Phosphocreatine/metabolism , Urea/metabolism
10.
Aquat Toxicol ; 86(2): 185-96, 2008 Jan 31.
Article in English | MEDLINE | ID: mdl-18068826

ABSTRACT

The objective of this study was to elucidate the mechanisms of acute ammonia toxicity in the aquatic Chinese soft-shelled turtle, Pelodiscus sinensis, and to examine how this turtle defended against a sublethal dose of NH(4)Cl injected into its peritoneal cavity. The ammonia and glutamine contents in the brains of turtles that succumbed within 3h to an intraperitoneal injection with a lethal dose (12.5 micromolg(-1) turtle) of NH(4)Cl were 21 and 4.4 micromolg(-1), respectively. Since the brain glutamine content increased to 8 micromolg(-1) at hour 6 and recovered thereafter in turtles injected with a sub-lethal dose of NH(4)Cl (7.5 micromolg(-1) turtle), it can be concluded that increased glutamine synthesis and accumulation was not the major cause of acute ammonia toxicity in P. sinensis. Indeed, the administration of l-methionine S-sulfoximine (MSO; 82 microgg(-1) turtle), a glutamine synthetase (GS) inhibitor, prior to the injection of a lethal dose of NH(4)Cl had no significant effect on the mortality rate. Although the prior administration of MSO led to an extension of the time to death, it was apparently a result of its effects on glutamate dehydrogenase and glutamate formation, instead of glutamine synthesis and accumulation, in the brain. By contrast, a prior injection with MK801 (1.6 microgg(-1) turtle), a NMDA receptor antagonist, reduced the 24h mortality of turtles injected with a lethal dose of NH(4)Cl by 50%. Thus, acute ammonia toxicity in P. sinensis was probably a result of glutamate dysfunction and the activation of NMDA receptors. NMDA receptor activation could also be exacerbated through membrane depolarization caused by the extraordinarily high level of ammonia (21 micromolg(-1) brain) in the brain of turtles that succumbed to a lethal dose of NH(4)Cl. One hour after the injection with a sub-lethal dose of NH(4)Cl, the brain of P. sinensis exhibited an extraordinarily high tolerance of ammonia (16 micromolg(-1) brain). The transient nature of ammonia accumulation indicates that P. sinensis could ameliorate ammonia toxicity through the suppression of endogenous ammonia production and/or the excretion of exogenous ammonia. Despite being ureogenic and ureotelic, only a small fraction of the exogenous ammonia was detoxified to urea. A major portion of ammonia was excreted unchanged, resulting in an apparent ammonotely in the experimental turtles. Since there were increases in total essential free amino acid contents in the brain, liver and muscle, it can be deduced that a suppression of amino acid catabolism had occurred, reducing the production of endogenous ammonia and hence alleviating the possibility of ammonia intoxication.


Subject(s)
Ammonium Chloride/metabolism , Ammonium Chloride/toxicity , Brain/drug effects , Turtles , Amino Acids/analysis , Ammonia/analysis , Ammonium Chloride/administration & dosage , Animals , Brain/enzymology , Brain/metabolism , Dizocilpine Maleate/pharmacology , Enzyme Inhibitors/pharmacology , Excitatory Amino Acid Antagonists/pharmacology , Glutamate Dehydrogenase/analysis , Glutamate Dehydrogenase/metabolism , Glutamate-Ammonia Ligase/analysis , Glutamate-Ammonia Ligase/metabolism , Liver/chemistry , Methionine Sulfoximine/pharmacology , Muscles/chemistry , Urea/analysis , Water/analysis
11.
Aquat Toxicol ; 85(1): 76-86, 2007 Nov 15.
Article in English | MEDLINE | ID: mdl-17881067

ABSTRACT

This study aimed to determine how the African lungfish Protopterus aethiopicus defended against ammonia toxicity when confronted with high concentrations (30 or 100 mmoll(-1)) of environmental ammonia. Exposure to 100 mmoll(-1) of NH(4)Cl for 1 or 6 days had no significant effect on the rate of O(2) uptake from water or from air, and the rate of total O(2) consumption. Using an Ussing-like apparatus, we report for the first time that the skin of P. aethiopicus had low permeability (1.26 x 10(-4) micromol min(-1)cm(-1)) to NH(3)in vitro. Indeed, the influx of exogenous ammonia into fish exposed to 30 mmoll(-1) NH(4)Cl was low (0.117 micromol min(-1) 100g(-1) fish). As a result, P. aethiopicus could afford to maintain relatively low ammonia contents in plasma, muscle, liver and brain even after 6 days of exposure to 100 mmoll(-1) NH(4)Cl. Surprisingly, fish exposed to 30 or 100 mmoll(-1) NH(4)Cl had comparable ammonia contents in the muscle and the brain in spite of the big difference (70 mmoll(-1)) in environmental ammonia concentrations. Significant increases in urea contents occurred in various tissues of fish exposed to 30 mmoll(-1) NH(4)Cl for 6 days, but there were no significant differences in tissue urea contents between fish exposed to 30 mmoll(-1) and 100 mmoll(-1) NH(4)Cl. Between days 3 and 6, the rate of urea excretion in fish exposed to 30 mmoll(-1) NH(4)Cl was significantly greater than that of the control. By contrast, there was no significant difference in urea excretion rates between fish exposed to 100 mmoll(-1) NH(4)Cl and control fish throughout the 6-day period, and such a phenomenon has not been reported before for other lungfish species. Thus, our results suggest that P. aethiopicus was capable of decreasing the NH(3) permeability of its body surface when exposed to high concentrations of environmental ammonia. Indeed, after 6 days of exposure to 100 mmoll(-1) NH(4)Cl, the NH(3) permeability constant of the skin (0.55 x 10(-4) micromol min(-1)cm(-1)) decreased to half of that of the control. A decrease in the already low cutaneous NH(3) permeability and an increased urea synthesis, working in combination, allowed P. aethiopicus to effectively defend against environmental ammonia toxicity without elevating the plasma ammonia level. Therefore, unlike other fishes, glutamine and alanine contents did not increase in the muscle and liver, and there was no accumulation of glutamine in the brain, even when the fish was immersed in water containing 100 mmoll(-1) NH(4)Cl.


Subject(s)
Ammonia/toxicity , Environmental Exposure , Fishes/physiology , Oxygen Consumption/drug effects , Water Pollutants, Chemical/toxicity , Amino Acids/blood , Ammonia/metabolism , Animals , Female , Male , Permeability/drug effects , Skin/drug effects , Skin/metabolism , Urea/analysis , Urea/metabolism , Water Pollutants, Chemical/metabolism
12.
Physiol Biochem Zool ; 78(4): 630-40, 2005.
Article in English | MEDLINE | ID: mdl-15957117

ABSTRACT

The African sharptooth catfish Clarias gariepinus lives in freshwater, is an obligatory air breather, and can survive on land during drought. The objective of this study was to elucidate how C. gariepinus defends against ammonia toxicity when exposed to terrestrial conditions. During 4 d of aerial exposure, there was no accumulation of urea in its tissues, and the rate of urea excretion remained low. Thus, exposure to terrestrial conditions for 4 d did not induce ureogenesis or ureotely in C. gariepinus. Volatilization of NH(3) was not involved in excreting ammonia during aerial exposure. In addition, there were no changes in levels of alanine in the muscle, liver, and plasma of C. gariepinus; nor were there any changes in the glutamine levels in these tissues. However, there were extraordinarily high levels of ammonia in the muscle (14 micromol g(-1)), liver (18 micromol g(-1)), and brain (11 micromol g(-1)) of fish exposed to terrestrial conditions for 4 d. This is the first report on a fish adopting high tolerance of ammonia in cells and tissues as the single major strategy to defend against ammonia toxicity during aerial exposure. At present, it is uncertain how C. gariepinus tolerates such high levels of ammonia, especially in its brain, but it can be concluded that, contrary to previous reports on two air-breathing catfishes (Clarias batrachus and Heteropneustes fossilis) from India, C. gariepinus does not detoxify ammonia to urea or free amino acids on land.


Subject(s)
Acclimatization/physiology , Air , Ammonia/metabolism , Catfishes/physiology , Alanine/blood , Alanine/metabolism , Analysis of Variance , Animals , Brain/metabolism , Catfishes/metabolism , Glutamine/blood , Glutamine/metabolism , Liver/metabolism , Muscle, Skeletal/metabolism , Time Factors , Urea/metabolism
13.
Eur Respir J ; 24(3): 371-4, 2004 Sep.
Article in English | MEDLINE | ID: mdl-15358693

ABSTRACT

The aim of the present study was to determine if patients with both pulmonary arterial hypertension (PAH), due to pulmonary vascular obstructive disease, and congenital heart defects (CHD), have mutations in the gene encoding bone morphogenetic protein receptor (BMPR)-2. The BMPR2 gene was screened in two cohorts: 40 adults and 66 children with PAH/CHD. CHDs were patent ductus arteriosus, atrial and ventricular septal defects, partial anomalous pulmonary venous return, transposition of the great arteries, atrioventicular canal, and rare lesions with systemic-to-pulmonary shunts. Six novel missense BMPR2 mutations were found in three out of four adults with complete type C atrioventricular canals and in three children. One child had an atrial septal defect and patent ductus arteriosus; one had an atrial septal defect, patent ductus arteriosus and partial anomalous pulmonary venous return; and one had an aortopulmonary window and a ventricular septal defect. Bone morphogenetic protein receptor 2 mutations were found in 6% of a mixed cohort of adults and children with pulmonary arterial hypertension/congenital heart defects. The current findings compliment recent reports in mouse models implicating members of the bone morphogenetic protein/transforming growth factor-beta pathway inducing cardiac anomalies analogous to human atrioventricular canals, septal defects and conotruncal congenital heart defects. The small number of patients studied and the ascertainment bias inherent in selecting for pulmonary arterial hypertension require further investigation.


Subject(s)
Heart Defects, Congenital/complications , Heart Defects, Congenital/genetics , Hypertension, Pulmonary/complications , Hypertension, Pulmonary/genetics , Mutation, Missense/genetics , Protein Serine-Threonine Kinases/genetics , Adult , Bone Morphogenetic Protein Receptors, Type II , Child , Cohort Studies , Humans , Receptors, Cell Surface/genetics , Sequence Analysis, DNA
14.
J Comp Physiol B ; 174(7): 555-64, 2004 Oct.
Article in English | MEDLINE | ID: mdl-15316727

ABSTRACT

This study aimed to elucidate the role of urea synthesis in the slender African lungfish Protopterus dolloi in detoxifying ammonia after feeding. There were significant increases in the rate of ammonia excretion in P. dolloi between hours 6 and 15 after feeding. Simultaneously, there were significant increases in urea excretion rates between hours 3 and 18. Consequently, the percentage of total nitrogen (N) excreted as urea N increased to approximately 60% between hours 12 and 21 post-feeding. Hence, after feeding, the normally ammonotelic P. dolloi became ureotelic. Approximately 41% of the N intake from food was excreted within 24 h by P. dolloi, 55% of which was in the form of urea N. At hour 12 post-feeding, the accumulation of urea N was greater than the accumulation of ammonia N in various tissues, which indicates that feeding led to an increase in the rate of urea synthesis. This is contrary to results reported previously on the infusion of ammonia into the peritoneal cavity of the marine dogfish shark, in which a significant portion of the exogenous ammonia was excreted as ammonia. In contrast, feeding is more likely to induce urea synthesis, which is energy intensive, because feeding provides an ample supply of energy resources and leads to the production of ammonia intracellularly in the liver. The capacity of P. dolloi to synthesize urea effectively prevented a postprandial surge in the plasma ammonia level as reported elsewhere for other non-ureogenic teleosts. However, there was a significant increase in the glutamine content in the brain at hour 24, indicating that the brain had to defend against ammonia toxicity after feeding.


Subject(s)
Ammonia/urine , Fishes/physiology , Postprandial Period , Urea/metabolism , Animals , Brain/metabolism , Diuresis , Fishes/metabolism , Fishes/urine , Glutamine/metabolism , Time Factors , Urea/urine
15.
J Comp Physiol B ; 174(2): 113-20, 2004 Mar.
Article in English | MEDLINE | ID: mdl-14610682

ABSTRACT

The Chinese fire-belly newt Cynops orientalis reverts to an aquatic mode of living when sexually mature. Despite living in water, sexually mature C. orientalis maintained high capacity for hepatic urea synthesis. However, it had a lower rate of urea production than other terrestrial amphibians because endogenous ammonia could diffuse out to the external medium as NH3. This conserves cellular energy because urea synthesis is energetically expensive. Simultaneously, C. orientalis also reduced the rate of urea excretion, and excreted 33% of the total nitrogenous waste as ammonia. Upon exposure to land, C. orientalis increased the rate of urea synthesis from accumulating endogenous ammonia. The increased rate of urea synthesis was within the inherent capacity of the hepatic ornithine-urea cycle; there was no induction of hepatic carbamoyl phosphate synthetase or ornithine transcarbamoylase activities and there was no reduction in ammonia production. When exposed to water containing 75 mmol.l(-1) NH4Cl, the rates of both urea synthesis and urea excretion increased. Under such experimental conditions, the ornithine-urea cycle may be operating close to its limit; glutamine began to accumulate in the body, and endogenous ammonia production via amino acid catabolism was reduced.


Subject(s)
Nitrogen/metabolism , Salamandridae/metabolism , Ammonia/metabolism , Animals , Environment , Female , Immersion , Male , Salamandridae/growth & development , Sexual Maturation , Soil , Urea/metabolism , Water
16.
J Appl Physiol (1985) ; 95(3): 991-8, 2003 Sep.
Article in English | MEDLINE | ID: mdl-12754172

ABSTRACT

Chest clapping, vibration, and shaking were studied in 10 physiotherapists who applied these techniques on an anesthetized animal model. Hemodynamic variables (such as heart rate, blood pressure, pulmonary artery pressure, and right atrial pressure) were measured during the application of these techniques to verify claims of adverse events. In addition, expired tidal volume and peak expiratory flow rate were measured to ascertain effects of these techniques. Physiotherapists in this study applied chest clapping at a rate of 6.2 +/- 0.9 Hz, vibration at 10.5 +/- 2.3 Hz, and shaking at 6.2 +/- 2.3 Hz. With the use of these rates, esophageal pressure swings of 8.8 +/- 5.0, 0.7 +/- 0.3, and 1.4 +/- 0.7 mmHg resulted from clapping, vibration, and shaking respectively. Variability in rates and "forces" generated by these techniques was <20% in average coefficients of variation. In addition, clinical experience accounted for 76% of the variance in vibration rate (P = 0.001). Cardiopulmonary physiotherapy experience and layers of towel used explained approximately 79% of the variance in clapping force (P = 0.004), whereas age and clinical experience explained >80% of variance in shaking force (P = 0.003). Application of these techniques by physiotherapists was found to have no significant effects on hemodynamic and most ventilatory variables in this study. From this study, we conclude that chest clapping, vibration, and shaking 1). can be consistently performed by physiotherapists; 2). are significantly related to physiotherapists' characteristics, particularly clinical experience; and 3). caused no significant hemodynamic effects.


Subject(s)
Hemodynamics/physiology , Physical Therapy Modalities , Respiratory Mechanics/physiology , Thorax/physiology , Vibration/adverse effects , Adult , Anesthesia , Animals , Body Mass Index , Female , Humans , Male , Peak Expiratory Flow Rate/physiology , Physical Stimulation , Sheep , Tidal Volume/physiology
17.
Mol Cell Endocrinol ; 185(1-2): 73-9, 2001 Dec 20.
Article in English | MEDLINE | ID: mdl-11738796

ABSTRACT

Obesity and related metabolic disorders are prevalent health issues in modern society and are commonly attributed to lifestyle and dietary factors. However, the mechanisms by which environmental factors modulate the physiological systems that control weight regulation and the aetiology of metabolic disorders, which manifest in adult life, may have their roots before birth. The 'fetal origins' or 'fetal programming' paradigm is based on the observation that environmental changes can reset the developmental path during intrauterine development leading to obesity and cardiovascular and metabolic disorders later in life. The pathogenesis is not based on genetic defects but on altered genetic expression as a consequence of an adaptation to environmental changes during fetal development. While many endocrine systems can be affected by fetal programming recent experimental studies suggest that leptin and insulin resistance are critical endocrine defects in the pathogenesis of programming-induced obesity and metabolic disorders. However, it remains to be determined whether postnatal obesity is a consequence of programming of appetite regulation and whether hyperphagia is the main underlying cause of the increased adiposity and the development of metabolic disorders.


Subject(s)
Appetite/physiology , Obesity/embryology , Prenatal Exposure Delayed Effects , Animals , Endocrine Glands/embryology , Endocrine Glands/physiopathology , Female , Fetus/physiopathology , Humans , Insulin Resistance/physiology , Leptin/physiology , Obesity/etiology , Pregnancy
18.
Ann Acad Med Singap ; 30(1): 15-21, 2001 Jan.
Article in English | MEDLINE | ID: mdl-11242618

ABSTRACT

INTRODUCTION: The purpose of this prospective study is to determine the effects of a pulmonary rehabilitation programme (PRP) conducted at our centre for patients with chronic lung disease. MATERIALS AND METHODS: Thirty-four patients (27 men and 7 women, mean age 67.7 years) with predominantly moderate-to-severe chronic obstructive pulmonary disease (31 patients), bronchiectasis (2 patients) and interstitial lung disease (1 patient) completed a 6-week outpatient PRP that included education, physical and respiratory care instruction and supervised exercise training. Outcome assessment was performed at baseline, on completion of PRP and 3 months after PRP. Physiologic measures included pulmonary function, incremental exercise and 6-minute walk tests (6MWTs). Disease-specific quality of life was assessed using the Chronic Respiratory Disease Questionnaire (CRDQ). RESULTS: There was no significant change in resting spirometry or lung volumes after PRP. Maximal oxygen uptake and work-rate improved significantly after PRP by 132.4 mL kg-1 min-1 and 10.7 W, respectively. 6MWT distance improved significantly by a mean of 67.3 m (P < 0.0001). Maximum Borg dyspnoea scores decreased significantly by 1.2 +/- 0.5 (P < 0.038). All domains of the CRDQ completed by a sub-group of patients improved significantly and the total scores increased by a mean of 21.7 points at the end of the PRP. The improvements gained in maximal exercise capacity immediately following PRP were maintained in 17 patients who returned for repeat assessment 3 months after PRP. CONCLUSION: Patients who completed a comprehensive PRP at our centre showed significant increase in functional capacity, reduction of exertional dyspnoea and improvement in health status.


Subject(s)
Exercise , Lung Diseases, Obstructive/rehabilitation , Respiratory Therapy/methods , Adaptation, Physiological , Adaptation, Psychological , Adult , Aged , Female , Humans , Lung Diseases, Obstructive/diagnosis , Lung Diseases, Obstructive/psychology , Male , Middle Aged , Prognosis , Program Evaluation , Prospective Studies , Psychology , Rehabilitation Centers , Respiratory Function Tests , Severity of Illness Index , Treatment Outcome
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