bluuebunny/crossref_metadata_2025 huggingface dataset:
Contribution Of Nitric Oxide, Cyclic Gmp And K+ Channels To Acetylcholine‐Induced Dilatation Of Rat Conduit And Resistance Arteries
Authors: Woodman Owen L , Wongsawatkul Orapin , Sobey Christopher G
Published: March 2003

1. We compared the effects of inhibiting nitric oxide synthase (NOS), soluble guanylate cyclase (sGC) and K+ channel activation on dilator responses to acetylcholine (ACh) in rat resistance (hindquarters) and conduit arteries (thoracic aorta).

2. In rat perfused hindquarters, the NO synthase inhibitor Nω‐nitro‐L‐arginine (L‐NNA; 1 mmol/L) partially inhibited the ACh‐induced dilatation and the combination of L‐NNA + haemoglobin (Hb; 20 μmol/L), a NO scavenger, did not further affect the response. Exposure to high K+ (30 mmol/L) also inhibited the response to ACh and this response was further reduced by L‐NNA + high K+. Surprisingly, when applied alone 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ), an inhibitor of sGC, did not affect responses to ACh, whereas treatment with ODQ + high K+ markedly impaired dilatation.

3. In aortic rings precontracted with phenylephrine (PE; 0.01–1 μmol/L), the maximum relaxation to ACh was significantly reduced by L‐NNA (0.1 mmol/L) and further inhibited by L‐NNA + Hb (20 μmol/L). At 10 μmol/L, ODQ alone inhibited the maximum relaxation to ACh, which was further reduced by ODQ + high K+ (30 mmol/L). High K+ caused a smaller but significant inhibition of ACh‐induced relaxation.

4. These results suggest that NO and cGMP play a relatively greater role in ACh‐induced dilatation of the aorta compared with the hindquarters resistance vasculature and are consistent with the hypothesis that a non‐NO endothelium‐derived hyperpolarizing factor (endothelium‐derived hyperpolarizing factor; EDHF) makes a relatively greater contribution to dilatation of resistance vessels than in conduit arteries. The data suggest that when sGC is inhibited, a compensatory mechanism involving K+ channel opening by NO can largely maintain ACh‐induced vasodilator responses of resistance vessels. Furthermore, when NO synthesis is blocked, a non‐ NO EDHF may play a role in ACh‐induced dilatation of the resistance vasculature.
Formation Of The Aqueous Humor
Authors: Macknight Anthony Dc , McLaughlin Charles W , Peart David , Purves Robert D , Carré David A , Civan Mortimer M
Published: March 2003

1. Glaucoma is a worldwide disease affecting approximately 1–2% of the population aged over 35 years in industrial countries and is a major cause of blindness.

2. Glaucoma is usually associated with an increased intra‐ocular pressure reflecting an imbalance between the rate of production of fluid (the aqueous humor) by the ciliary epithelial cells and its drainage from the eye. Therefore, it is important to understand how this secretion is produced. This requires a knowledge of ciliary epithelial cell composition, which has, in the past, proved difficult to obtain in mammalian preparations.

3. We have recently used the technique of electron‐probe X‐ray microanalysis to determine this composition under a variety of in vitro conditions.

4. Our results have led to a new model for this secretion that emphasizes the potential secretory role of the Na+/K+/2Cl– cotransporter.
Nitric Oxide Production And Hepatic Dysfunction In Patients With Postoperative Sepsis
Authors: Satoi Sohei , Kamiyama Yasuo , Kitade Hiroaki , Kwon A‐Hon , Takahashi Kanji , Wei Tu , Inoue Tomohisa , Takahashi Hakuo
Published: March 2003

1. Although hepatic function is well known to deteriorate following bacterial infection, the underlying mechanisms remain poorly understood. We have previously reported that nitric oxide (NO) radical leads to a decrease in the ketone body ratio (KBR) and in ATP content due to the inhibition of mitochondrial electron transport in primary cultured rat hepatocytes.

2. To evaluate the effects of NO radical on the liver in patients with postoperative sepsis, we analysed both the stable end‐product of nitric oxide radical (NOx) as well as the arterial KBR (AKBR), which reflects liver tissue NAD+/NADH.

3. Twenty patients who had undergone general abdominal surgery and who developed postoperative sepsis were divided into two groups: (i) surviving; and (ii) non‐surviving. Blood samples were collected before the development of postoperative sepsis and every 3 days until the patient either died or was discharged from hospital.

4. Plasma NOx levels in seven patients who subsequently died became progressively higher than those in the 13 surviving patients over the clinical course of postoperative sepsis.

5. In the non‐surviving group, the AKBR was significantly lower than in surviving patients, indicating impaired hepatic function. In contrast, plasma NOx levels in non‐surviving patients were significantly higher than in surviving patients.

6. Decreases in AKBR to levels below 0.7 in non‐surviving patients followed high NOx levels. Moreover, plasma NOx levels were closely correlated with the AKBR, indicating that NO radical is associated with mitochondrial dysfunction in the liver.

7. It is likely that the overproduction of NO radical plays an important role in causing fatal metabolic disorders in patients with postoperative sepsis.
Cardiac And Vascular Responses In Deoxycorticosterone Acetate‐Salt Hypertensive Rats
Authors: Brown Lindsay , Ooi Sze‐Yuan , Lau Kevin , Sernia Conrad
Published: March 2003

1. Hypertension leads to ventricular hypertrophy and, eventually, to heart failure. The present study has investigated the functional consequences of deoxycorticosterone acetate (DOCA)‐salt hypertension in rats by defining the inotropic, chronotropic and vascular responses to noradrenaline (NA; β1‐adrenoceptor agonist), forskolin (adenylate cyclase activator) and theophylline (phosphodiesterase inhibitor).

2. Administration of DOCA (25 mg, s.c., every 4th day) and excess salt (1% NaCl in drinking water) to uninephrectomized rats increased left ventricular wet weight by 35 and 71% after 4 and 8 weeks, respectively. Addition of KCl (0.4%) or CaCl2 (1%) in the drinking water for 4 weeks attenuated blood pressure increases, but not ventricular weight increases (46 and 28%, respectively).

3. Positive inotropic responses in papillary muscles from uninephrectomized rats to NA (–log EC50 6.73±0.38; n = 7), forskolin (–log EC50 6.15±0.31; n = 7) and CaCl2 (–log EC50 2.40±0.02; n = 14) were unchanged in hypertrophied left ventricles of DOCA and DOCA‐CaCl2 rats, although maximal responses to NA were decreased in DOCA‐KCl rats (1.2±0.6 mN, n = 8; DOCA‐salt 2.9±0.5 mN, n = 6); theophylline was less potent in DOCA‐salt rats. Positive chronotropic responses to NA, forskolin and theophylline in right atria and negative inotropic responses to carbachol in papillary muscles were unchanged.

4. Maximal vasoconstrictor responses to NA in thoracic aortic rings were reduced in DOCA‐KCl rats to 2.4±0.9 mN (n = 5), but were increased in DOCA‐CaCl2 rats to 26.6±2.2 mN (n = 7; DOCA‐salt 7.8±2.2 mN, n = 9). Vasorelaxant responses to forskolin and theophylline were unchanged.

5. These results show that cardiac responses are only minimally affected during the development of DOCA‐salt hypertension‐induced hypertrophy, despite the reported decreases in adenylate cyclase activity, in these rats. This is in contrast with the decreased responses reported in other rat models of cardiac hypertrophy and in the failing human heart. Thus, hypertrophy in hearts of DOCA‐salt hypertensive rats does not produce similar changes to the failing human heart.
Beneficial Effects Of Fish Oil On Glucose Metabolism In Spontaneously Hypertensive Rats
Authors: Ajiro Koji , Sawamura Makoto , Ikeda Katsumi , Nara Yasuo , Nishimura Masayoshi , Ishida Hitoshi , Seino Yutaka , Yamori Yukio
Published: March 2003

1. Increased interest in fish oil led us to examine their metabolic effects in spontaneously hypertensive rats, which have been reported to have glucose intolerance.

2. Rats were divided into three groups: (i) a control group fed standard rat laboratory chow; (ii) a lard group fed a high‐fat diet containing 20% lard; and (iii) a fish oil group fed a high‐fat diet containing 20% fish oil for 14 weeks.

3. Systolic blood pressure and fasting blood glucose were markedly increased in the lard group, whereas in the fish oil group they were only transiently increased at the beginning and decreased to levels seen in the control group.

4. Intraperitoneal glucose tolerance test demonstrated that fish oil reversed the impairment of glucose disposal found in the lard group. However, plasma insulin levels were raised transiently at 30 min in the fish oil group compared with the control group.

5. Insulin secretion from pancreatic islets stimulated with glucose in vitro was also enhanced by fish oil.

6. These results lead us to conclude that fish oil improves glucose tolerance by enhancing insulin secretion from pancreatic β‐cells.
Tonic Potentiation And Attenuation Produced By Membrane Depolarization In Guinea‐Pig Trachealis
Authors: Yamaki Kenichi , Ogawa Masahiro , Ito Yasushi
Published: March 2003

1. We studied how membrane depolarization directly affected intracellular Ca2+ signalling when voltage‐operated Ca2+ channels (VOCC) were not available in guinea‐pig tracheal smooth muscle. To block VOCC, we used 3 μmol/L verapamil, which completely abolished high K+ (20–60 mmol/L)‐induced contraction, and elevation of fura‐2 signal.

2. Muscle tone was generated by adding Ca2+ to the extracellular Ca2+‐free solution containing prostaglandin (PG)E2 (100 nmol/L) after abolishing basal tone with indomethacin (1 μmol/L).

3. In the absence of verapamil, high K+ (20–60 mmol/L) solution potentiated 2.4 mmol/L Ca2+‐induced sustained contractions. Even in the presence of 3 μmol/L verapamil, replacement with 20 and 40 mmol/L K+ solution induced tonic potentiation, which was changed to attenuation with a higher K+ solution (60 mmol/L), lower extracellular Ca2+ concentration ([Ca2+]o) and pretreatment with cyclopiazonic acid (10 μmol/L), a Ca2+ sequestration inhibitor.

4. These results indicate that the balance between depolarization‐dependent Ca2+ release and receptor‐operated cation channel inhibition may determine whether tonic potentiation or attenuation is manifested, depending on the availability of VOCC, the magnitude of the depolarization, [Ca2+]o and Ca2+ content in the sarcoplasmic reticulum.
Stress‐Induced Elevation Of The St Segment In The Rat Electrocardiogram Is Normalized By An Adrenoceptor Blocker
Authors: Ueyama T , Yoshida K , Senba E
Published: March 2003

1. Emotional stress is one of the aetiologies of cardiac accidents, but the precise mechanisms remain to be elucidated. In the present study we used the immobilization stress model in rats to investigate electrocardiographic (ECG) changes.

2. A rapid elevation of the ST segment at the II, III, aVF and precordial leads in the ECG was found and this returned to prestress basal levels after removal of stress.

3. This ECG change was normalized by combined blockade of α‐ and β‐adrenoceptors, but not by administration of a potent coronary vasodilator, such as a calcium channel blocker or nitroglycerin.

4. These results suggest that direct activation of cardiac adrenoceptors by stress may result in angina‐like ECG changes.
Atrial Tachyarrhythmias Induced By Acetylcholine In Tilapia (Oreochromis SP.) Isolated Atria
Authors: Lin Tsai‐Chu , Hou Zone‐Yuan , Liu Hwan‐Wun , Wu Hui‐Sun , Lin Cheng‐I
Published: March 2003

1. Effects of the parasympathetic neuromediator acetylcholine (ACh) on atrial tissues vary greatly depending on the species, the type of atrial cells and experimental conditions. The aim of the present study was to investigate, with microelectrode techniques, the arrhythmogenic effects of ACh in tilapia (Oreochromis sp.) isolated atria at room (22–25°C) and high temperature (37°C).

2. Acetylcholine (1–10 μmol/L) shortened action potential duration (APD), depressed action potential plateau and decreased twitch force in tilapia atria, as it did in human atrial fibres. In addition, ACh induced premature responses and re‐entrant tachyarrhythmias (TA; frequency range from 7 to 25 Hz) in five of 19 and 14 of 22 tilapia atria tested at room and high temperature, respectively. The higher incidence of ACh‐induced TA at 37°C compared with room temperature was statistically significant.

3. The ACh‐induced TA consisted of high‐frequency and uniform action potentials accompanied by tension oscillation and elevation of diastolic force (flutter). Acetylcholine‐induced TA could be readily abolished by atropine (1 μmol/L) and prevented by treatment with agents with local anaesthetic properties, such as 0.1 μmol/L tetrodotoxin or 3 μmol/L quinidine. The antagonistic action of quinidine occurred without significant prolongation of APD.

4. The present findings suggest that pharmacological concentrations of the cholinergic muscarinic agonist ACh readily induce TA (mainly atrial flutter) in tilapia atria, presumably via sodium channel‐dependent re‐entrant excitation. The poikilothermic tilapia appears to be an appropriate animal model for the study of atrial TA.
Area Postrema And Sympathetic Nervous System Effects Of Vasopressin And Angiotensin II
Authors: Hasser Eileen M , Cunningham J Thomas , Sullivan Margaret J , Curtis Kathleen S , Blaine Edward H , Hay Meredith
Published: March 2003

1. Precise control over the cardiovascular system requires the integration of both neural and humoral signals related to blood volume and blood pressure. Humoral signals interact with neural systems, modulating their control over the efferent mechanisms that ultimately determine the level of pressure and volume.

2. Peptide hormones such as angiotensin (Ang)II and arginine vasopressin (AVP) act through circumventricular organs (CVO) to influence cardiovascular regulation.

3. The area postrema (AP), a CVO in the brainstem, mediates at least some of the central actions of these peptides. Vasopressin appears to act in the AP to cause sympathoinhibition and a shift in baroreflex control of the sympathetic nervous system (SNS) to lower pressures. These effects of AVP and the AP appear to be mediated by α2‐adrenoceptor and glutamatergic mechanisms in the nucleus tractus solitarius.

4. In contrast to AVP AngII has effects in the AP to blunt baroreflex control of heart rate and cause sympathoexcitation. The effects of chronic AngII to increase activity of the SNS may be due to AP‐dependent activation of neurons in the rostral ventrolateral medulla.
Centrally Produced Nitric Oxide And The Regulation Of Body Fluid And Blood Pressure Homeostases
Authors: Kadekaro Massako , Summy‐Long Joan Y
Published: March 2003

1. Nitric oxide (NO) tonically inhibits the basal release of vasopressin and oxytocin into plasma.

2. Nitric oxide inhibition on vasopressin secretion is removed, while that on oxytocin is enhanced, during water deprivation, hypovolaemia, moderate osmotic stimulation and angiotensin (Ang)II. This results in a preferential release of vasopressin over oxytocin that promotes conservation of water.

3. Nitric oxide facilitates drinking behaviour stimulated by water deprivation, osmotic stimulation, haemorrhage and AngII. Together with the hormonal response, NO produces a positive water balance during reductions in intracellular and intravascular volumes.

4. Nitric oxide produced within the central nervous system maintains resting arterial blood pressure partially by attenuating the pressor actions of AngII and prostaglandins.

5. Central production of NO is enhanced during osmotic stimulation to counterbalance the salt‐induced pressor response.

6. Paradoxically, central production of NO is also enhanced during haemorrhage, presumably to maintain peripheral vasodilation and blood flow to vital organs.
Anteroventral Third Ventricle Periventricular Tissue Contributes To Cardiac Baroreflex Responses
Authors: Bealer Steven L
Published: March 2003

1. The studies reviewed in the present paper demonstrate that the anteroventral third ventricle (AV3V) region contains tissue that can modify cardiac baroreflex sensitivity in response to circulating angiotensin (Ang)II and hyperosmolality.

2. The response to hyperosmolality appears to be mediated by noradrenergic receptors. Although the role of noradrenergic receptors in the AV3V region in modification of baroreflex‐induced responses to AngII has not been directly tested, this neurotransmitter is a good candidate for control of heart rate because noradrenaline in the AV3V region is critical for mediating other responses to AngII.

3. Results from studies indicate that the AV3V region is part of a central nervous system circuit involved in modulation of cardiac baroreflex sensitivity by circulating substances, possibly acting at the organum vasculosum lamina terminalis.

4. The findings extend the role of the AV3V periventricular tissue as a central site integrating autonomic nervous system function by demonstrating that this brain area contributes to cardiac function, in addition to its well‐characterized role in sympathetic nervous system regulation of blood pressure and mechanisms of fluid and electrolyte regulation.
Enalapril Prevents Aortic Hyperreactivity And Remodelling In One‐Kidney, One‐Clip Hypertensive Rats Without Reducing Arterial Pressure
Authors: Cunha Valdeci , Salgado Helio C , Salgado Maria Cristina O
Published: March 2003

1. The present study was designed to evaluate the blood pressure‐independent effects of angiotensin‐converting enzyme (ACE) inhibition on cardiovascular structure and function in one‐kidney, one‐clip (1K1C) hypertensive rats.

2. The study was conducted in four groups of rats: (i) uninephrectomized normotensive rats (1K); (ii) 1K1C hypertensive rats; (iii) 1K rats treated with enalapril; and (iv) 1K1C rats treated with enalapril. Enalapril treatment (20 mg/kg per day, p.o.) was started after surgery to induce hypertension or nephrectomy and continued for 5 weeks.

3. The increase in blood pressure of 1K1C rats was associated with activation of cardiac and aortic, but not plasma, ACE activity and with hypertrophy of both heart and aorta. No difference in cardiac output and in vitro systolic function was observed among the groups. Hypertrophied aorta isolated from 1K1C rats displayed increased sensitivity to phenylephrine (PE) and unaltered responses to both acetylcholine (ACh) and sodium nitroprusside compared with the 1K group.

4. Enalapril treatment effectively inhibited plasma and tissue ACE activity in 1K1C and 1K rats. Enalapril did not prevent the development of hypertension and cardiac hypertrophy nor did it change haemodynamic parameters in 1K1C rats. However, enalapril prevented the increase in aortic media thickness and cross‐sectional area and restored the hypersensitivity to PE in aortic rings of 1K1C rats. The endothelium‐dependent response to ACh was enhanced by enalapril in the aorta of 1K but not 1K1C rats.

5. These results suggest a role for activated local angiotensin II generation in aortic but not cardiac hypertrophy secondary to 1K1C hypertension.
Neuronal Response To Physical Injury And Its Relationship To The Pathology Of Alzheimer’s Disease
Authors: King Ce , Adlard Pa , Dickson Tc , Vickers Jc
Published: March 2003

1. Central nerve cells undergo a stereotyped regenerative response following physical injury.

2. This reaction involves adaptive changes within the axon and cell body of origin, directed at sprouting and synaptogenesis.

3. Intimately associated with the regenerative response are specific alterations to cytoskeletal proteins, including the neurofilament (NF) triplet.

4. The morphological and neurochemical alterations to NF within axons following injury are reminiscent of plaque‐ associated dystrophic neurites (DN) in early Alzheimer’s disease (AD).

5. Associated changes in perikaryal NF resemble Alzheimer neurofibrillary tangle pathology, while growth‐associated sprouting markers are localized to the abnormal neurites of AD.

6. The present review postulates that β‐amyloid plaques in AD cause physical damage to local nerve cell processes and it is the chronic stimulation of the stereotyped response to injury that results in the end‐stage pathology and neurodegeneration associated with AD.
Bedside Perspectives On The Use Of Opioids: Transferring Results Of Clinical Research Into Practice
Authors: Ravenscroft Peter , Schneider Jennifer
Published: March 2003

1. Transference of research findings to clinical practice has been a challenge for those managing chronic pain. Generally, pain is not well controlled in hospitals and steps need to be taken to make pain control more effective.

2. Clinical trials of opioids have shown that pain can be controlled in the great majority of patients. Apart from the use of the World Health Organization Analgesic Ladder, a ‘pain diagnosis’ should be made and a comprehensive view of pain needs to be considered by the clinician. This would include pain and other physical symptoms, psychological issues and social and spiritual stresses.

3. Respiratory depression and tolerance for opioids are often seen as negative aspects of opioids and, therefore, may lead to inadequate control of pain. The evidence cited suggests that, in the long‐term treatment of cancer pain, respiratory depression almost never occurs. The only situation that warrants caution is when an anaesthetic block or similar procedure relieves pain treated by opioids, when that patient has been receiving large doses of opioids. Long‐term studies with opioids show that tolerance may occur, but is not a clinical problem and should not impair their use in adequate doses to relieve the patient’s pain.

4. The active morphine metabolites, morphine‐3‐glucuronide (M3G) and morphine‐6‐glucuronide (M6G) do need to be considered when administering morphine. There seems to be considerable interindividual variation in the production and elimination of metabolites. In cases of renal failure or in the elderly, the ratios of M3G and M6G to morphine accumulate exponentially, making opioid toxicity more likely. Even different routes of administration seem to be associated with different ratios of metabolites. A knowledge of these sources of pharmacokinetic variability may lead to more effective use of the opioids in clinical practice.
A New Method For Simultaneous Measurements Of Mast Cell Proteases In Human Vascular Tissue
Authors: Takai Shinji , Sakaguchi Masato , Jin Denan , Miyazaki Mizuo
Published: March 2003

1. Human mast cells contain carboxypeptidase A, chymase and tryptase. In the present study, in order to analyse the mast cell proteases simultaneously, we investigated a method for the measurement of carboxypeptidase A, chymase and tryptase in human vascular tissues.

2. Human vascular tissues were homogenized in 10 mmol/L phosphate buffer containing 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6 or 1.8 mol/L KCl and 0.1% non‐idet P‐40 and samples were then extracted. Because carboxypeptidase A and chymase convert angiotensin (Ang)I to Ang‐(1–9) and AngII, respectively, the extracts were incubated with AngI in the presence of an angiotensin‐converting enzyme (ACE) inhibitor. The extract prepared in buffer with over 0.8 mol/L KCl converted AngI to Ang‐(1–9) and AngII. Formation of Ang‐(1–9) and AngII plateaued in extracts with 1.0 and 1.2 mol/L KCl, respectively.

3. The formation of Ang‐(1–9) and AngII in the extract with 1.2 mol/L KCl was inhibited by inhibitors of carboxypeptidase A and chymase, respectively, suggesting that Ang‐(1–9) and AngII were generated from AngI by carboxypeptidase A and chymase, respectively.

4. Using a specific tryptase substrate, tryptase activity was detected in extract in buffer with over 0.8 mol/L KCl and reached a plateau at concentrations of KCl over 1.0 mol/L.

5. These findings show that the maximum activity of carboxypeptidase A, chymase and tryptase was detected in extracts of human homogenized vascular tissues in buffer at 1.2 mol/L KCl. The present study demonstrates a new method for the simultaneous measurement of proteases derived from mast cells in humans.
Activity Of The Na+/H+ Exchanger Contributes To Cardiac Damage Following Ischaemia And Reperfusion
Authors: Allen Dg , Xiao X‐H
Published: March 2003

1. The present review considers the evidence that Na+–H+ exchange activity contributes to cardiac damage following ischaemia and reperfusion. The basic mechanism involved is that protons are produced during ischaemia and leave the myocytes on the Na+/H+ exchanger during either ischaemia and/or reperfusion. The resulting elevation of [Na+]i causes Ca2+ loading through the Na+/Ca2+ exchanger and the elevated [Ca2+]i is thought to lead to myocardial damage.

2. Inhibition of the Na+/H+ exchanger during ischaemia and/or reperfusion produces a substantial cardioprotective effect by blocking the damage caused by the coupled exchanger mechanism described above. Preconditioning also produces a cardioprotective effect and the evidence that this also involves the Na+/H+ exchanger is reviewed.

3. The intracellular mechanisms associated with ischaemic damage and preconditioning are of great interest because they may provide targets for potential therapeutic interventions. The intracellular regulation of the Na+/H+ exchanger appears to be an important component of these pathways and may become a focus for therapeutic approaches.
Role For Capillaries In Coupling Blood Flow With Metabolism
Authors: Sarelius Ingrid H , Cohen Kenneth D , Murrant Coral L
Published: March 2003

1. Skeletal muscle blood flow is coupled with metabolism; for this coupling to be effective in matching blood flow to capillary exchange, control of capillary blood flow and recruitment must reside at the capillary level.

2. Capillaries are, indeed, capable of sensing and responding to vasoactive stimuli. We report studies that indicate that contraction of skeletal muscle fibres underneath capillaries is capable of increasing blood flow in those capillaries.

3. This presumed metabolically related signal initiates remote dilations in arterioles upstream of the stimulated capillaries. Our findings indicate that the vasodilatory signal is transmitted along the blood vessel wall.

4. Although we present evidence supporting a role for gap junctionally mediated communication of this vasodilatory signal, it appears unlikely to be primarily electrotonic spread of membrane potential changes.

5. Our studies further indicate that the transmitted signal is not dependent on changes in endothelial cell calcium.
Glomerular Expression Of Endothelial Nitric Oxide Synthase In Deoxycorticosterone Acetate‐ Salt‐Treated Rats
Authors: Tsuchiya Ken , Naruse Mitsuhide , Nihei Hiroshi
Published: March 2003

1. In the present study, we investigated the relationship between chronic volume loading and glomerular endothelial nitric oxide synthase (eNOS) expression. Immunohistochemical expression of eNOS in glomeruli was semiquantified by graded scores of staining intensity. Each glomerulus was isolated by microdissection and mRNA expression was detected by reverse transcription–polymerase chain reaction (RT‐PCR) in desoxycorticosterone acetate (DOCA)‐salt‐treated rats.

2. Glomerular expansion and dilatation of tubules were the main histological findings and glomerular and vascular injury scores were significantly higher in the DOCA‐salt‐treated group than in the control group. Endothelial NOS staining in glomeruli in DOCA‐salt‐treated animals was 81.4% lower than in control animals. Endothelial NOS mRNA was also detected at a very low rate in the kidney of treated rats compared with control rats (22/80 vs 74/80 glomeruli, respectively).

3. These results suggest that eNOS protein and mRNA expression in glomeruli was reduced by DOCA‐salt loading. Chronic volume loading may damage the glomerulus and this may be mediated, at least in part, by disruption of eNOS.
Ischaemic Preconditioning Ameliorates Functional Disturbance And Impaired Renal Perfusion In Rat Ischaemia–Reperfused Kidneys
Authors: Ogawa Toshihisa , Mimura Yoshikazu , Hiki Naoki , Kanauchi Hajime , Kaminishi Michio
Published: March 2003

1. The effects of ischaemic preconditioning (IP) on renal function, haemodynamics and lipid peroxidation in the rat ischaemia–reperfused kidney model were examined.

2. In Wistar male rats, application of a single or three periods of 5 min bilateral renal ischaemia was performed prior to 30 min bilateral ischaemia and 90 min reperfusion (IR). The glomerular filtration rate (GFR) was estimated in terms of inulin clearance. Fractional excretion of sodium (FENa) and lithium (FELi), indicating total and proximal tubular sodium handling, respectively, was also measured and renal blood flow was monitored throughout the experiment. In addition, renal lipid peroxidation (LPO) levels in reperfused kidneys were evaluated.

3. A 2.8‐fold increase in recovery of GFR (P < 0.005), a 50% reduction in FENa (P < 0.005) and a 40% decrease in FELi (P < 0.05) after IR resulted from the single period of 5 min IP. Renal blood flow was also higher than that in the control group (P < 0.01). No change of LPO levels was observed.

4. We conclude that IP may have an ability to ameliorate reperfused renal function and haemodynamics with a suitable period of preconditioned ischaemia, although this effect is independent of LPO.
Neural Regulation Of Renal Blood Flow: A Re‐Examination
Authors: Malpas Simon C , Leonard Bridget L
Published: March 2003

1. The importance of renal sympathetic nerve activity (RSNA) in the regulation of renal function is well established. However, it is less clear how the renal vasculature responds to the different mean levels and patterns of RSNA. While many studies have indicated that small to moderate changes in RSNA preferentially regulate renin secretion or sodium excretion and only large changes in RSNA regulate renal blood flow (RBF), other experimental evidence suggests that small changes in RSNA can influence RBF

2. When RSNA has been directly measured in conjunction with RBF, it appears that a range of afferent stimuli can induce reflex changes in RBF. However, many studies in a variety of species have measured RBF only during stimuli designed to reflexly increase or decrease sympathetic activity, but have not recorded RSNA. While this approach can be informative, it is not definitive because the ability of the vasculature to respond to RSNA may, in part, reflect the resting level of RSNA and, therefore, the vasoconstrictive state of the vasculature under the control conditions.

3. Further understanding of the control of RBF by RSNA has come from studies that have analysed the underlying rhythms in sympathetic nerve activity and their effect on the cardiovascular system. These studies show that the frequency–response characteristic of the renal vasculature is such that higher frequency oscillations in RSNA (above 0.6 Hz) contribute to setting the mean level of RBF. In comparison, lower frequency oscillations in RSNA can induce cyclic vasoconstriction and dilation in the renal vasculature, thus inducing oscillations in RBF.

4. In summary, the present review discusses the neural control of RBF, summarizing evidence in support of the hypothesis that RBF is under the influence of RSNA across the full range of RSNA.
Experimental Biology 2000 Symposium on Differential Control of Sympathetic Outflow A DEFENCE‐LIKE REACTION: AN EMERGENT PROPERTY OF A SYSTEM OF COUPLED NON‐LINEAR OSCILLATORS
Authors: Gebber Gerard L
Published: March 2003

1. The present paper deals with the central mechanisms responsible for the defence‐like differential pattern of spinal sympathetic outflow elicited by electrical activation of the mid‐brain periaqueductal grey (PAG) in urethane‐anaesthetized, baroreceptor‐denervated cats. The pattern is characterized by increases in the 10 Hz discharges of the inferior cardiac (CN) and renal (RN) sympathetic nerves and a decrease in 10 Hz activity of the vertebral sympathetic nerve (VN) that supplies vasoconstrictor outflow to the forelimb.

2. The model used to explain this pattern is based on the self‐organizing properties of a system of coupled brainstem oscillators rather than the activation of point‐to‐point hard‐wired connections leading to increases in sympathetic outflow to some targets and decreases to others.

3. The fact that VN 10 Hz activity was inhibited by PAG stimulus frequencies equal to or just above, but not just below, that of the free‐running (control) rhythm argues against a ‘hard‐wired’ model.

4. The evidence supporting the hypothesis that the defence‐like pattern is an emergent property of a system of coupled oscillators includes changes in the phase lag of VN 10 Hz activity relative to that in the CN, temporal correlation of the changes in phase angle and 10 Hz powers and the direct relationship between the magnitude of the change in phase angle and the degree to which PAG stimulation reciprocally affected the 10 Hz discharges of the CN and VN.

5. It is proposed that changes in phase angle reflect the reorganization of the coupling of 10 Hz oscillators and that such changes in state lead to differential patterns of spinal sympathetic outflow.
Proceedings of the Australian Physiological and Pharmacological Society Symposium: Ion Channels GENETICS, AN ALTERNATIVE WAY TO DISCOVER, CHARACTERIZE AND UNDERSTAND ION CHANNELS
Authors: Schofield Peter R
Published: March 2003

1. The conventional approach to understanding the structure and properties of ion channels has been to use physiological characterization.

2. Purification and molecular cloning of ion channel genes has enabled more detailed structure–function analyses to be undertaken.

3. An alternative approach to the identification of genes of pathophysiological importance has been the use of genetic linkage approaches and positional cloning or positional candidate analysis of ion channel genes.

4. Using genetic approaches, mutations have been described that cause inherited neurological disorders of neurons (e.g. epilepsy, migraine, deafness, ataxia and startle disease), skeletal muscle (myotonia, malignant hyperthermia, periodic paralysis and myasthenia) and cardiac muscle (long QT syndrome and ventricular fibrillation).

5. For each disease, gene structure–function analyses of the mutant alleles have provided further insights into the biology of ion channels.

6. The present brief review examines the methods used in genetic linkage studies and positional cloning of disease genes. Understanding how ion channel gene mutations give rise to dysfunctional channels will be important in defining and treating the episodic and chronic channelopathies.
Inhibitory Effect Of Reactive Oxygen Species On Angiotensin I‐Converting Enzyme (Kininase II)
Authors: Michel B , Grima M , Nirina Lb , Ingert C , Coquard C , Barthelmebs M , Imbs Jl
Published: March 2003

1. Somatic angiotensin I‐converting enzyme (ACE) is a protein that contains two similar domains (N‐ and C‐terminal), each possessing an active site. We have examined the effects of a generator of hydroxyl radicals (g•OH: 2,2′‐azo‐bis(2‐amidinopropane)) and hydrogen peroxide (H2O2) on ACE using an in vitro approach.

2. The generator of hydroxyl radicals inactivated ACE in a time (2–6 h)‐ and concentration (0.3–3 mmol/L)‐dependent manner at 37°C. When ACE was coincubated for 4 h with g•OH (3 mmol/L), its activity decreased by 70%. Addition of dimethylthiourea or mannitol + methionine, two •OH scavengers, resulted in a significant protection of ACE activity. Mercaptoethanol and dithiotreitol, two thiol‐reducing agents, also efficiently protected ACE activity.

3. The hydrolysis of two natural and domain‐specific substrates was explored. The hydrolysis of angiotensin I, preferentially cleaved by the C‐domain, was significantly inhibited (57–58%) after 4 h exposure to g•OH (0.3–1 mmol/L). Under the same conditions of exposure, the hydrolysis of N‐acetyl‐Ser‐Asp‐Lys‐Pro, a specific substrate for the N‐domain, was only slightly inhibited by 1 mmol/L g•OH.

4. Hydrogen peroxide, another source of •OH, was used. After exposure to H2O2 (3 mmol/L; 4 h), an 89% decrease in ACE activity was observed. Pretreatment with the iron chelator deferoxamine (1 mmol/L) attenuated H2O2‐mediated ACE inactivation, demonstrating that the effect of H2O2 was partly due to its conversion into •OH (Fenton reaction).

5. In summary, our findings demonstrate that g•OH and H2O2 inhibit ACE activity and suggest a preferential action of g•OH on the C‐domain of the enzyme.
Annual Scientific Meeting of ASCEPT, 1999 Careful Screening To Target Interventions To Prevent Sudden Cardiac Death
Authors: Struthers Allan D
Published: March 2003

1. Cardiac death is due not only to coronary artery disease, but also to left ventricular (LV) abnormalities (fibrosis, dysfunction) and arrhythmogenic triggers, such as autonomic imbalance.

2. Nitric oxide deficiency could be a key mediator leading not only to coronary atherosclerosis, but also to LV abnormalities and autonomic imbalance.

3. It may be possible to screen for the above abnormalities (e.g. echocardiography and brain natriuretic peptide levels for LV abnormalities, 24 h tapes for autonomic imbalance and QT interval analysis).

4. Once individuals are identified as being at high risk, a range of interventions is possible (e.g. intensive statin therapy or angiotensin‐converting enzyme inhibitors if LV abnormalities or autonomic imbalance are found).
Role Of Protein Kinase C, KATP Channels And Dna Fragmentation In The Infarct Size‐Reducing Effects Of The Free Radical Scavenger T‐0970
Authors: Hashimoto Kazuaki , Minatoguchi Shinya , Hashimoto Yasuko , Wang Ningyuan , Qiu Xinbin , Yamashita Kazuya , Uno Yoshihiro , Arai Masazumi , Nishida Yoshio , Takemura Genzou , Suzuki Toshikazu , Fujiwara Takako , Fujiwara Hisayoshi
Published: March 2003

1. In the present study, we investigated the effect of 1‐(3‐ tert‐butyl‐2‐hydroxy‐5‐methoxyphenyl)‐3‐(3‐pyridylmethyl) urea hydrocloride (T‐0970), a novel water‐soluble low‐molecular weight free radical scavenger, on the generation of hydroxyl radicals in vivo and on myocardial infarct size in an in vivo model of myocardial infarction in rabbits.

2. T‐0970 scavenged hydroxyl radicals generated in the myocardium during reperfusion, as assessed by using a microdialysis technique and HPLC in an in vivo model with 30 min coronary occlusion and 30 min reperfusion in rabbits.

3. Another group of rabbits was subjected to 30 min coronary occlusion and 48 h reperfusion. The control group (n = 10) was infused with saline for 190 min from 10 min before occlusion to 180 min after reperfusion. The treatment group (T‐0970 group; n = 10) was injected with a bolus 2.5 mg/kg T‐0970 and then infused with T‐0970 for 190 min from 10 min before reperfusion to 180 min after reperfusion at a rate of 100 μg/kg per min. The T‐0970 + CHE group (n = 5) was given chelerythrine (CHE; a selective inhibitor of protein kinase C (PKC); 5 mg/kg, i.v.) 10 min before the administration of T‐0970. The T‐0970 + 5‐HD group (n = 5) was given 5‐hydroxydecanoate (5‐HD; an inhibitor of mitochondrial KATP channels; 5 mg/kg, i.v.) 10 min before the administration of T‐0970. The CHE and 5‐HD groups were given CHE (5 mg/kg, i.v.) and 5‐HD (5 mg/kg, i.v.) 20 min before reperfusion, respectively. After 48 h reperfusion, infarct size was measured histologically and expressed as a percentage of the area at risk (AAR). In another series of experiments, the control (n = 5) and T‐0970 (n = 5) groups were killed 4 h after reperfusion following 30 min coronary occlusion and DNA fragmentation in myocytes was assessed using in situ dUTP nick end‐labelling (TUNEL) at the light microscopic level.

4. Infarct size, as a percentage of AAR, in the T‐0970 group was significantly reduced compared with the control group (21±4 vs 41±4%, respectively; P < 0.05). This reduction of infarct size by T‐0970 was abolished by pretreatment with CHE and 5‐HD. Neither CHE nor 5‐HD alone had any effect on infarct size. The percentage of infarcted myocytes with DNA fragmentation by TUNEL in the T‐0970 group was significantly reduced compared with the number in the control group (4.0±1.5 vs 10.7±1.9%, respectively; P < 0.05).

5. T‐0970, a free radical scavenger, improved reperfusion injury. This effect seemed to be mediated by activation of PKC, the opening of mitochondrial KATP channels and inhibition of DNA fragmentation.
Role Of Nitric Oxide On Pressor Mechanisms Within The Dorsomedial And Rostral Ventrolateral Medulla In Anaesthetized Cats
Authors: Chen Shu‐Ying , Mao Shih‐Peng , Chai Chok‐Yung
Published: March 2003

1. The role of nitric oxide (NO) in central cardiovascular regulation and the correlation between NO and glutamate‐induced mechanisms is not clear. Microinjection of glutamate (3 nmol/ 30 nL) into dorsomedial medulla (DM) and rostral ventrolateral medulla (RVLM) increased arterial blood pressure (BP) and sympathetic vertebral nerve activity (VNA). Thus, in the present study, we examined the modulation by NO of glutamate‐induced pressor responses in the DM and RVLM of cats.

2. Histochemical methods using nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) as a marker to stain neurons containing NO synthase (NOS), showed positive findings of NOS in both the DM and RVLM.

3. Microinjection of NG‐nitro‐L‐arginine methyl ester (L‐NAME), a NOS inhibitor, into the DM or RVLM did not alter resting BP and VNA, but it did cause a dose‐dependent attenuation of glutamate‐induced pressor responses. Interestingly, the increase in NO levels that resulted from pretreatment with L‐arginine (L‐Arg) or sodium nitroprusside (SNP) did not alter resting BP and VNA, but still inhibited glutamate‐induced pressor responses in the DM and RVLM in a dose‐dependent manner.

4. We also examined whether NO modulated the pressor responses induced by activation of different excitatory amino acid receptors. N‐Methyl‐D‐aspartate (NMDA) and α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole proprionic acid (AMPA) were used. Consistent with the results from the initial glutamate studies, we observed that not only L‐NAME, but also L‐Arg and SNP attenuated pressor responses induced by NMDA and AMPA. No difference was found between the effects of NO on NMDA‐ and AMPA‐induced pressor responses.

5. To investigate the possibility of a loss of agonist selectivity, the effects of D‐2‐amino‐5‐phosphonovalerate (D‐AP5) and 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) on AMPA and NMDA responses in the DM were examined. The results showed that CNQX did not alter NMDA‐induced pressor responses, while D‐AP5 failed to alter AMPA‐induced responses.

6. Our results suggest that activation of the glutamate‐induced pressor mechanism is regulated by changes in NO levels in the DM and RVLM. This implies that NO may play a permissive role to allow operation of the glutamate‐activation mechanism.
Effect of 9‐(6,7‐Dideoxy‐β‐D‐Allo‐Hept‐5‐Ynofuranosyl)Adenine On Noradrenaline Release From Vascular Sympathetic Nerves
Authors: Shinozuka Kazumasa , Ishii‐Nozawa Reiko , Takeuchi Koichi , Minakawa Noriaki , Matsuda Akira , Nakata Hiroyasu , Kunitomo Masaru
Published: March 2003

1. The effects of 9‐(6,7‐dideoxy‐β‐D‐allo‐hept‐5‐ynofuranosyl)adenine (HAK2701), a selective and potent ligand for P3 receptor‐like protein, on the release of endogenous noradrenaline (NA) from electrically stimulated rat mesenteric artery and rabbit ear artery were compared with those of a number of purinoceptor agonists.

2. In the rat mesenteric artery, the P1 receptor agonists 2‐chloroadenosine (2CA) and 5′‐N‐ethylcarboxamidoadenosine (NECA) and the P2 purinoceptor agonists β,γ‐methylene ATP (βγmATP) and 2‐methylthio ATP (2mSATP) significantly inhibited the release of NA in a xanthine‐sensitive manner. HAK2701 did not significantly inhibit the release of NA, the relative order of potency being βγmATP > NECA > 2CA > 2mSATP >> HAK2701.

3. In the rabbit ear artery, both P1 and P2 receptor agonists significantly facilitated the release of NA in a xanthine‐sensitive manner. HAK2701 also significantly facilitated the release of NA, the relative order of potency being HAK2701 > βγmATP > 2CA > 2mSATP > NECA.

4. These findings suggest that HAK2701 may be a potent and selective agonist for facilitatory prejunctional purinoceptors, but not for inhibitory purinoceptors, on adrenergic nerve terminals.
Extracellular ATP and cAMP as Paracrine and Interorgan Regulators of Renal Function ATP Release Mechanisms, ATP Receptors and Purinergic Signalling along the Nephron
Authors: Schwiebert Erik M
Published: March 2003

1. Autocrine and paracrine signalling along the nephron of the kidney has been a widely held hypothesis for several decades. The lumen of the nephron is an ideal autocrine and paracrine signalling microenvironment. Any agonist, filtered at the glomerulus or released in the proximal tubule or other proximal segments, is subsequently trapped in the lumen of the nephron and present to interact with luminal receptors. Similar signalling in the renal interstitium is also possible and likely. Indeed, receptors for many autocrine and paracrine agonists have been characterized on the luminal membrane and serosal membrane of multiple nephron segments.

2. An important family of autocrine and paracrine agonists in the kidney are the purinergic agonists. Extracellular ATP, as well as its metabolites (ADP, 5′‐AMP and adenosine), is released by renal epithelial cells. These compounds are also freely filtered at the glomerulus and are found in the final urine. Receptors for ATP and adenosine are also expressed on the luminal and serosal side of many nephron segments.

3. The present review discusses purinergic signalling by nucleotide agonists in an integrated manner, from ATP release to ATP receptors to extracellular ATP‐mediated effects on renal epithelial function. These themes are the focus of our laboratory in normal and polycystic kidneys as well as in normal and diseased epithelial cells from other tissues. The physiological roles of extracellular purinergic signalling in the kidney and other tissues are only beginning to emerge.
Effects In Humans Of Intravenously Administered Endotoxin On Soluble Cell‐Adhesion Molecule And Inflammatory Markers: A Model Of Human Diseases
Authors: Wilson Mf , Blum R , Dandona P , Mousa Sa
Published: March 2003

1. Endotoxin, a component of the cell wall of Gram‐negative bacteria, could be a predisposing mediator of many pathological disorders. The present study was undertaken to determine the effects and time‐course of acute endotoxin challenge on inflammatory and cell‐adhesion molecule markers shedding in the plasma as potential surrogates.

2. Six normal male subjects per group (age range 21–35 years) were injected with 4 ng/kg, i.v., reference standard Escherichia coli (0113:h10:k) endotoxin or physiological saline.

3. Plasma inflammatory markers (tumour necrosis factor (TNF)‐α, interleukin (IL)‐6 and TNF‐receptor I (RI)) and cell‐adhesion molecule markers (soluble L‐selectin, soluble P‐selectin, soluble vascular cell adhesion molecule (VCAM)‐1) were determined using sensitive and specific ELISA.

4. Tumour necrosis factor‐α increased from a basal level of 2.8 pg/mL to approximately 800 pg/mL at 90 min after endotoxin. Similarly, IL‐6 peaked 2–3 h after endotoxin injection, with a rapid decline by 6–8 h, and levels returned to basal values by 24 h.

5. In contrast, TNF‐RI peaked at 2 h (increasing from basal levels of 900–3300 pg/mL) with a much slower decline and without return to basal levels at 24 h (1400 pg/mL).

6. Endotoxin resulted in a rapid rise in soluble L‐selectin within 1 h, which increased from a basal of 150–425 ng/mL. This rapid rise in soluble L‐selectin was sustained for up to 2.5 h and then rapidly declined to basal levels by 3.5 h.

7. In contrast, plasma soluble P‐selectin levels showed a delayed and progressive increase up to 8 h (increasing from a basal level of 50–95 ng/mL), with a partial decline at 24 h (80 ng/mL).

8. Similarly, soluble VCAM‐1 levels showed a progressive rise up to 24 h (increasing from basal values of 600–1000 ng/mL).

9. This acute human model of endotoxin exposure demonstrated an upregulation of inflammatory stimuli leading to a short‐term hyperactivation of leucocytes and a more sustained activation of platelets and endothelium.

10. This model provides a non‐invasive method for studying the complex effects of endotoxin‐like pathogens on different cellular events using soluble plasma surrogate markers.