Abstract:
:Transport of a number of dipolar amino acids (and the orally active antibiotic D-cycloserine) across the apical membrane of human intestinal epithelial (Caco-2) cell monolayers is mediated by a Na+-independent, pH-dependent transport mechanism. Relatively little is known about the mode of action of this transport system so to differentiate between pH dependence and proton coupling three experimental protocols were designed and tested. The results demonstrate, firstly, that it is the transapical pH gradient and its maintenance (rather than apical acidity alone) that is important in amino acid uptake. Secondly, Na+-independent uptake of seven dipolar amino acids (with pKa (-log of acid dissociation constant) values between 1 50 and 4 23) showed a similar dependence on apical pH (half-maximal uptake being observed at pH 5 99-6 20). Thirdly, the pattern of pH-dependent amino acid ([beta]-alanine) uptake is similar irrespective of whether the cationic substrate concentration is varied or constant, demonstrating no relationship between uptake and concentration of the cationic form of the amino acid. These observations demonstrate that the transport mechanism is a H+-zwitterionic amino acid symporter and suggest that the presence of a H+ gradient at the apical surface of the human small intestine (in the form of the acid microclimate) may be important in driving nutrient absorption.
journal_name
Exp Physioljournal_title
Experimental physiologyauthors
Thwaites DT,Stevens BCsubject
Has Abstractpub_date
1999-03-01 00:00:00pages
275-84issue
2eissn
0958-0670issn
1469-445Xjournal_volume
84pub_type
杂志文章abstract::Despite its critical role in restoring cardiac rhythm and thus in saving human life, cardiac defibrillation remains poorly understood. Further mechanistic inquiry is hampered by the inability of presently available experimental techniques to resolve, with sufficient accuracy, electrical behaviour confined to the depth...
journal_title:Experimental physiology
pub_type: 杂志文章,评审
doi:10.1113/expphysiol.2005.030973
更新日期:2006-03-01 00:00:00
abstract:NEW FINDINGS:What is the central question of this study? Can low-dose inorganic nitrate supplementation prevent testicular structural and functional alterations in streptozotocin-induced type 1 diabetic male rats? What is the main finding and it's important? Treatment with a low dose of inorganic nitrate for 2 months h...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/EP087198
更新日期:2018-12-01 00:00:00
abstract::A global and transient rise of intracellular Ca2+ (Ca2+i) is central to the operation of pump-leak coupling in the frog early distal tubule (EDT). The endoplasmic reticulum (ER) is the site of this Ca2+ release and reuptake; however, it is likely that other intracellular pools, such as mitochondria, also contribute to...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.2004.028886
更新日期:2005-03-01 00:00:00
abstract::Simultaneous portal blood absorption and intestinal mucosal catabolism of labelled fatty acids were investigated. Anaesthetized adult Wistar rats were infused intraduodenally either with 90 mumol of capric (C10:0), oleic (C18:1), linoleic (C18:2) or arachidonic (C20:4) 1-14C acids or with 30 mumol of each labelled fat...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.1991.sp003511
更新日期:1991-05-01 00:00:00
abstract::Recently attempts have been made to analyse blood pressure (BP) and renal sympathetic nerve activity (RSNA) to determine how patterns contained within them might reflect control by the autonomic nervous system. To date, these studies have primarily used coherence analysis of BP and RSNA in the frequency domain. Howeve...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1111/j.1469-445x.2002.tb00059.x
更新日期:2002-07-01 00:00:00
abstract::Embryonic stem (ES) cells are pluripotent cells isolated from the inner cell mass of blastocysts. ES cells are able to differentiate into the three primitive layers (endoderm, mesoderm and ectoderm) of the organism, including the germline. To study early stages of development, as well as to investigate the impact of a...
journal_title:Experimental physiology
pub_type: 杂志文章,评审
doi:
更新日期:2000-11-01 00:00:00
abstract:NEW FINDINGS:What is the central question of this study? Is chemerin, an adipokine implicated in obesity, increased in neonates following in utero cigarette smoke exposure. What is the main finding and its importance? Chemerin mRNA expression was increased and chemerin DNA methylation was decreased in babies born to mo...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/EP087307
更新日期:2019-01-01 00:00:00
abstract:NEW FINDINGS:What is the central question of this study? Although peripheral blood haematopoietic stem and progenitor cells are potentially important in regeneration after acute myocardial infarction, their self-renewal ability in the post-acute phase has not yet been addressed. What is the main finding and its importa...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/EP086643
更新日期:2018-01-01 00:00:00
abstract::We investigated the permeability of Cs+ and Na+ through various ion channels in rat atrial myocytes using the whole-cell voltage-clamp technique. With isotonic CsCl (140 mM) on both sides of the membrane and nominally [Ca2+]o-free conditions, depolarising clamp pulses induced an increase of outward currents which show...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:
更新日期:2000-03-01 00:00:00
abstract:NEW FINDINGS:What is the topic of this review? The manuscript collectively combines the experimental observations from >100 publications focusing on the regulation of cerebral blood flow and metabolism during exercise from 1945 to the present day. What advances does it highlight? This article highlights the importance ...
journal_title:Experimental physiology
pub_type: 杂志文章,评审
doi:10.1113/EP086249
更新日期:2017-11-01 00:00:00
abstract::Mechanical properties of the vascular smooth muscle from normal and dystrophin-deficient (mdx) mice were examined. Changes in resting and developed tensions in response to stretch were recorded in isolated portal vein. The vascular segments were elongated in 5 % increments of the 'in situ' length (Lr) up to 1.30Lr. Th...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:
更新日期:1999-09-01 00:00:00
abstract::This review explores the current concepts relating the structural and functional modifications of skeletal muscle mitochondria to the molecular mechanisms activated when organisms are exposed to a hypoxic environment. In contrast to earlier assumptions it is now established that permanent or long-term exposure to seve...
journal_title:Experimental physiology
pub_type: 杂志文章,评审
doi:10.1113/eph8802513
更新日期:2003-01-01 00:00:00
abstract::Exercise performance in hypoxia may be limited by a critical reduction in cerebral and skeletal tissue oxygenation, although the underlying mechanisms remain unclear. We examined whether increased systemic free radical accumulation during hypoxia would be associated with elevated microvascular deoxygenation and reduce...
journal_title:Experimental physiology
pub_type: 杂志文章,随机对照试验
doi:10.1113/expphysiol.2014.081265
更新日期:2014-12-01 00:00:00
abstract::Experiments were performed to investigate, in the normal and acutely inflamed rabbit knee joint, the role of prostaglandins in the regulation of joint blood flow, measured by laser Doppler flowmetry, as well as their modulation of sympathetic vasoconstriction. Close intra-arterial injection of prostaglandin E2 (PGE2) ...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.1994.sp003745
更新日期:1994-01-01 00:00:00
abstract::Changes in tension of slow motor units in the medial gastrocnemius muscle of the rat were measured and compared in three fatigue tests, each of 4 min duration. In one of these tests motor unit tetani were evoked by repeated trains of stimuli of the standard frequency, 40 Hz, while in other tests frequencies of 20 and ...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.1995.sp003907
更新日期:1995-11-01 00:00:00
abstract::5-[5-(2-Nitrophenyl) furfuryliodine]-1,3-diphenyl-2-thiobarbituric acid (UCF-101) is a protease inhibitor which was reported to protect against ischaemic heart damage and apoptosis. This study evaluated the impact of UCF-101 on steptozotocin (STZ)-induced diabetic cardiomyocyte dysfunction. Adult FVB mice were made di...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.2009.049189
更新日期:2009-09-01 00:00:00
abstract::Neuropeptides and regulatory peptide hormones control many developmental, physiological and behavioural processes in animals, including humans. The nonapeptides oxytocin and arginine vasopressin are produced and released by the pituitary gland and have actions on many organs and tissues. Receptive cells possess partic...
journal_title:Experimental physiology
pub_type: 杂志文章,评审
doi:10.1113/expphysiol.2013.072561
更新日期:2014-01-01 00:00:00
abstract::The aims of this study were: (1) to determine the within-subject, between-day variability in end-tidal P(CO2) (P(ET,CO2)); (2) to determine whether the within-subject, between-day variability in P(ET,CO2) was caused by variations in metabolic acid-base status; and (3) to determine whether between-subject variations in...
journal_title:Experimental physiology
pub_type: 临床试验,杂志文章
doi:10.1113/eph8802585
更新日期:2003-09-01 00:00:00
abstract:NEW FINDINGS:What is the central question of this study? A transcranial magnetic stimulation (TMS)-induced twitch applied on isolated single breaths over the motor cortex somatotopic representation of the tongue briefly recruits submental muscles and improves airflow dynamics of flow-limited respiratory cycles without ...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.2013.073072
更新日期:2013-09-01 00:00:00
abstract:NEW FINDINGS:What is the central question of this study? Calcium is an important second messenger in eccrine sweating; however, whether modulation of extracellular Ca(2+) and Ca(2+) entry has the capacity to modulate sweat rate in non-glabrous human skin has not been explored. What is the main finding and its importanc...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.2013.076547
更新日期:2014-02-01 00:00:00
abstract::The role of bicarbonate as a hydrogen ion buffer has been investigated using the fluorescent dye BCECF in individual rat cerebellar, hippocampal and neocortical neurones maintained in culture. The steady-state intracellular pH (pHi) was estimated to be 7.07 +/- 0.05 (n = 22) in CO2-HCO3(-)-buffered media. Buffering po...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.1996.sp003963
更新日期:1996-07-01 00:00:00
abstract::Vasopressin and oxytocin release from the neural lobe, and the vasopressin and oxytocin mRNA contents of the supraoptic and paraventricular nuclei are increased by hypertonicity of the extracellular fluid. The factors regulating these parameters can be conveniently studied in perifused explants of the hypothalamo-neur...
journal_title:Experimental physiology
pub_type: 杂志文章,评审
doi:10.1111/j.1469-445x.2000.tb00021.x
更新日期:2000-03-01 00:00:00
abstract:NEW FINDINGS:What is the central question of this study? Does baroreceptor unloading during passive hyperthermia contribute to increases in ventilation and decreases in end-tidal carbon dioxide during that exposure? What is the main finding and its importance? Hyperthermic hyperventilation is not mitigated by expanding...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/EP085259
更新日期:2015-11-01 00:00:00
abstract::The renal medulla contains more mRNA of the inducible isoform of nitric oxide synthase (iNOS) than the cortex, which may be important in preventing ischaemic injury, since blood flow and tissue oxygen tension are normally low in this region. We examined the effects of the bacterial endotoxin E. coli lipopolysaccharide...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/eph8702289
更新日期:2002-03-01 00:00:00
abstract::Three experiments were performed to see whether cardiac neurons contribute to the intrinsic control of heart rate in right atria of adult rats. The intrinsic heart rate response (IRR) was examined by raising right atrial pressure from 2 to 8 mmHg for 3 min. In isolated preparations of the right atrium, the IRR was not...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/eph8702364
更新日期:2002-11-01 00:00:00
abstract::Lower body negative pressure (LBNP) reduces central venous pressure (CVP) and cardiac output. The elderly are reported to have a limited capacity to increase cardiac output by increasing heart rate (HR), are especially dependent on end diastolic volume to maintain stroke volume and therefore should be especially vulne...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/eph8602153
更新日期:2001-05-01 00:00:00
abstract::Hypertension caused by chronic infusion of angiotensin II (Ang II) in experimental animals is dependent, in part, on increased activity of the sympathetic nervous system. This chronic sympathoexcitatory response is amplified by a high-salt diet, suggesting an interaction of circulating Ang II and dietary salt on sympa...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.2011.060491
更新日期:2012-01-01 00:00:00
abstract::To elucidate the regulatory role of atrial natriuretic factor (ANF) on vasopressin (AVP) and aldosterone release in conscious rabbits, ANF was administered systematically at a rate of 15 pmol min-1 (kg body wt)-1 for 15 min in two series of experimental animals in which AVP and/or aldosterone production was stimulated...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.1992.sp003622
更新日期:1992-07-01 00:00:00
abstract:NEW FINDINGS:What is the central question of this study? Dexmedetomidine has a capacity for sedation, anti-anxiety and analgesia with minimal suppression of respiratory function; what is its role in neuropathic pain and what is the involvement of miRNAs? What is the main finding and its importance? Dexmedetomidine atte...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/EP088596
更新日期:2020-09-01 00:00:00
abstract::The role of testosterone (T) in the regulation of cardiovascular function in females is not well understood. Our goal was to examine the effect of T on cardiomyocyte biology by measuring sarcomere shortening/relaxation and intracellular calcium cycling in adult female Sprague-Dawley rats. The rats were divided into th...
journal_title:Experimental physiology
pub_type: 杂志文章
doi:10.1113/expphysiol.2012.067009
更新日期:2013-01-01 00:00:00