bluuebunny/crossref_metadata_2025 huggingface dataset:
ENDOTHELIUM‐DERIVED HYPERPOLARIZING FACTOR
Authors: Félétou Michel , Vanhoutte Paul M.
Published: June 2007

1. Not all endothelium‐dependent relaxation can be full explained by the release of either nitric oxide (NO) and/or prostacyclin. Another unidentified substance(s) that hyperpolarizes the underlying vascular smooth muscle cells (endothelium‐derived hyperpolarizing factor; EDHF) contributes to endothelium‐dependent relaxations.

2. In blood vessels from various species these hyperpolarizations are resistant to inhibitors of NO synthase (NOS) and cycl‐oxygenase. In canine, porcine and human blood vessels the hyperpolarization cannot be mimicked by nitrovasodilators or exogeneous NO. However, in other species (rat, guinea‐pig, rabbit) endothelium‐dependent hyperpolarizations resistant to inhibitors of NOS and cyclo‐oxygenase and hyperpolarizations to endothelium‐derived or exogeneous NO can be obsercved n the same vascular smooth muscle cells.

3. In blood vessels where NO causes hyperpolarization, the response is blocked by glibenclamide, suggesting the involvement of ATP‐dependent potassium channels. Hyperpolarizations caused by EDHF are insensitive to glibenclamide but, depending on the tissue, are inhibited by relatively small concentrations of tetraethylammonium (TEA) or by apamin or the combination of charybdotoxing plus apamin, indicating that calcium‐dependent potassium channels are likely to be involved.

4. Metabolites of arachidonic acid, through the cytochrome P450 mono‐oxygenase pathway (epoxyeicosatrienoic acids), are produced by the endothelial cells, increase the open‐state probability of calcium‐activated potassium channels sensitive to TEA or charybdotoxin, and induce the hyperpolarization of arterial smooth muscle cells, indicating that epoxyeicosatrienoic acids could be EDHF. However, in blood vessels from various species, cytochrome P450 inhibitors do not affect endothelium‐dependent hyperpolarizations, indicating that EDHF is not yet identified with certainty.

5. Endothelium‐derived hyperpolarizing factor released from cultured endothelial cells reduces the intracellular calcium concentration in vascular smooth muscle cells and the EDHF component of the relaxation is proportionally more important in smaller than larger arteries. In aging animals and in various models of diseases, endothelium‐dependent hyperpolarizations are diminished.

6. The identification of EDHF and/or the discovery of specific inhibitors of its synthesis and its action may allow a better understanding of its physiological and pathophysiological role(s).
REGULATION AND ROLE OF UROKINASE PLASMINOGEN ACTIVATOR IN VASCULAR REMODELLING
Authors: Tkachuk Vsevolod , Stepanova Victoria , Little Peter J. , Bobik Alex
Published: June 2007

1. Urokinase plasminogen activator (uPA) is produced and secreted by multiple vascular cell types, thus influencing the processes and the extent to which the vasculature is remodelled during the development of the intima or a neointima and during hypertrophy and angiogenesis.

2. Urokinase plasminogen activator mRNA expression is up‐ and down‐regulated by growth factors, cytokines and steroids. Urokinase plasminogen activator is secreted as a single chain inactive form that may be proteolytically converted to active or inactive forms. Targeting of proteolytic activity may occur via focalized expression of uPA and its cell surface receptors (uPAR). Proteolytic activity is also controlled through the often co‐ordinated expression of specific inhibitors.

3. A proteolytic cascade involving uPA provides its major role in tissue remodelling through the primary degradation of extracellular matrix and secondarily through the activation of transforming growth factor‐β or release from the matrix of basic fibroblast growth factor. In addition, uPA secreted by growth factor‐stimulated vascular cells may contribute to the chemotactic and mitogenic responses ascribed to the growth factor and recent evidence strongly suggests that uPA has direct biological actions on vascular cells.

4. The cell surface binding of uPA via its growth factor‐like domain to uPAR localizes and activates the protease, but may also initiate transmembrane signalling of biological responses, including migration/invasion and proliferation. As the uPAR lacks intracellular signalling domains, the signals may be transduced via interactions between uPA/uPAR and more classical signalling receptors. The mechanism by which uPA may be involved in cell signalling is yet to be elucidated.
DIRECT MEASUREMENT OF THE RELEASE OF ATP AND ITS MAJOR METABOLITES FROM THE NERVE FIBRES OF THE GUINEA‐PIG TAENIA COLI
Authors: McConalogue K. , Todorov L. , Furness JB , Westfall DP
Published: June 2007

1. The release of adenosine triphosphate (ATP), adenosine diphosphate, adenosine monophosphate and adenosine from guinea‐pig taenia coli in response to electrical stimulation of intramural nerves was measured directly using high performance liquid chromatography separation and fluorometric detection.

2. Purines were released in a frequency‐dependent manner by trains of transmural electrical pulses at 1‐30 Hz.

3. Electrically evoked release of ATP was abolished by tetrodotoxin (10−6 mol/L) but was not affected by nicardipine (10−6 mol/ L).

4. The release of purines was reduced in the presence of atropine.

5. Pituitary adenylyl cyclase‐activating peptide did not evoke the release of any purines and did not modify the electrically evoked release of purines.

6. The results suggest that ATP and its major metabolites are released from a neuronal source, possibly the enteric inhibitory nerves, in the guinea‐pig taenia coli.
TACHYCARDIA AFTER GLUTAMATE INJECTION IN RAT SPINAL CORD IS NOT BLOCKED BY KYNURENATE OR MIMICKED BY METABOTROPIC AGONISTS
Authors: Arnolda Leonard F. , Pilowsky Paul M. , Minson Jane B. , Llewellyn‐Smith Ida J. , Chalmers John P.
Published: June 2007

1. We have used microinjections of glutamate, an ionotropic excitatory amino acid receptor antagonist (kynurenate) and selective ionotropic (NMDA and kainate) and metabotropic (lS‐3R‐ACPD, trans‐ACPD and L‐AP4) receptor agonists in the thoracic IML of the rat to define the receptors mediating the tachycardia produced by excitatory amino acid agonists.

2. Injection of glutamate (Δ heart rate = 76±8 beats/min n = 16), NMDA (A heart rate = 116.5±5 beats/min n = 6) or kainate (Δ heart rate = 92±22 beats/min n = 6) evokes a tachycardia when injected into the thoracic intermediolateral column. Kynurenate blocked the response to NMDA (‐2% of initial response) and markedly attenuated the response to kainate (14% of initial response) but did not alter the response to glutamate (106% of initial response).

3. IS‐3R‐ACPD did not elicit a tachycardia when injected into the thoracic intermediolateral column and neither trans‐ACPD nor L‐AP4 induced a tachycardia after kynurenate injection into the thoracic intermediolateral column.

4. Thus stimulation of either NMDA or AMPA/kainate receptors elicits a tachycardia in rat thoracic spinal cord but glutamate also activates another receptor type to elicit a tachycardia. The lack of a tachycardia when trans‐ACPD1, 1S‐3RACPD or L‐AP4 were injected into the thoracic spinal cord suggests that the kynurenate resistant tachycardia elicited by glutamate is not mediated by metabotropic receptors. The kynurenate resistant tachycardia elicited by glutamate is not mediated by any of the known excitatory amino acid receptor types.
ON THE ANTIARRHYTHMIC ACTIONS OF MAGNESIUM IN SINGLE GUINEA‐PIG VENTRICULAR MYOCYTES
Authors: Song Yejia , Liu Qi‐Ying , Vassalle Mario
Published: June 2007

1. The hypotheses that magnesium quickly abolishes arrhythmias by acting as a calcium antagonist or by increasing outward potassium currents were tested in guinea‐pig isolated ventricular myocytes by recording membrane potentials and currents by means of a single microelectrode discontinuous voltage clamp method.

2. High [Mg2+]0 (4‐16 mmol/L) slightly increased the amplitude and duration of the action potential (AP) in some myocytes, but overall the changes were not significant.

3. High [Mg2+]0 did not decrease the slow inward current (Ica) and had little effect on voltage‐ and time‐dependent outward potassium currents whether or not Ica was allowed to flow.

4. Zero [Mg2+]0 decreased the duration, but not amplitude, of the AP. Zero [Mg2+]0 had little effect on Ica and on outward currents except for a small increase in outward current in the region of the negative slope of the inward rectifier currentvoltage relationship.

5. In our myocytes, in contrast to [Mg2+]0 high [Ca2+]0 significantly increased the amplitude and decreased the duration of the AP; at the same time, high [Ca2+]0 increases Ic2. and the outward potassium current.

6. High [Mg2+]0 decreased the amplitude of the oscillatory potentials (Vos) induced by various Ca2+‐over1oading procedures (high [Ca2+]0, noradrenaline, strophanthidin and barium).

7. It is concluded that the mechanisms by which high [Mg2+]0 quickly suppresses cardiac arrhythmias are related to an extracellular action of Mg2+ and do not include a block of ICa, or an increase in outward current. Mg2+ can be antiarrhythmic by decreasing Vos amplitude and possibly by screening the fixed negative charges at the external surface of the sarcolemma.
POSSIBLE INVOLVEMENT OF MUSCARINIC M1 AND M3 RECEPTOR SUBTYPES MEDIATING VASODILATION IN ISOLATED, PERFUSED CANINE LINGUAL ARTERIES
Authors: Chiba Shigetoshi , Tsukada Miyoko
Published: June 2007

1. Using the cannula insertion method, muscarinic receptor subtypes were analysed in isolated, perfused canine lingual arteries preconstricted with phenylephrine.

2. Both acetylcholine and McN‐A‐343 induced a profound vasodilation in a dose‐related manner. Acetylcholine‐induced dilations were approximately 1000‐times more potent than McN‐A‐343‐induced dilation.

3. Acetylcholine‐induced dilations were abolished after removal of the endothelium by intraluminal treatment with 1 mg saponin.

4. Acetylcholine‐induced dilations were markedly inhibited by an M1/M3 receptor antagonist, 4‐DAMP. Moreover, they were slightly, but significantly, inhibited by an M1 antagonist, pirenzepine, but never influenced by an M2 antagonist, AF‐DX 116. Mc‐N‐A‐343‐induced vasodilations were inhibited by both 4‐DAMP or pirenzepine.

5. These results suggest that there are abundant functional M3 and a few M1 receptors in the canine lingual artery that mediate vasodilation and that this vasodilation is dependent on the presence of an intact endothelium.
MECHANISMS OF MYOCARDIAL PROTECTION BY AMINO ACIDS: FACTS AND HYPOTHESES
Authors: Pisarenko Oleg I.
Published: June 2007

1. Positive inotropic effect of taurine and improvement of cardiac performance of failing heart are mediated through the modulation of Ca2+ movement through the sarcolemma.

2. Cardioprotection with glutamate and aspartate is related to enhanced anaerobic energy formation in mitochondria coupled with succinate formation and, probably, with the relieving of glycolytic flux. During reperfusion, both amino acids replenish the malate‐aspartate shuttle reactants, thereby facilitating glucose oxidation.

3. Increased intracellular concentrations of branched chain amino acids (leucine, valine and isoleusine) stimulate formation of acetyl‐coenzyme (CoA) and succinyl‐CoA and, thus, recovery of oxidative metabolism.

4. Methionine and cysteine enhance force of contraction by N‐methylation of membrane phospholipids of the sarcolemma and sarcoplasmic reticulum. Methionine and, to a lesser extent, cysteine may reduce myocardial damage by oxygen radical species.

5. Histidine exerts antioxidant properties as a scavenger of singlet oxygen and OH’ radicals. High concentrations of histidine provide intracellular buffering to stimulate anaerobic energy formation.
AUGMENTED ENDOTHELIUM‐DEPENDENT CONSTRICTION TO HYPOXIA EARLY AND LATE FOLLOWING REPERFUSION OF THE CANINE CORONARY ARTERY
Authors: Pearson Paul J. , Lin Pyng J. , Schaff Hartzell V. , Vanhoutte Paul M.
Published: June 2007

1. Canine coronary arteries with intact endothelium respond to hypoxaemia or serotonin infusion with dilatation, but when the endothelium is injured or dysfunctional, these stimuli can cause constriction. The present studies investigated whether or not regional ischaemia and reperfusion alter endotheliumdependent responsiveness of canine coronary arteries in vivo and in vitro.

2. In organ chamber experiments, isolated control and reperfused coronary artery rings were contracted with prostaglandin F2α and exposed to hypoxia (PO2 less than 5 mmHg).

3. Hypoxia augmented the response of reperfused arteries more than that of controls. The hypoxic augmentation was blocked by NG‐monomethyl‐L‐arginine, an inhibitor of nitric oxide synthesis from L‐arginine.

4. These findings demonstrate that early following coronary reperfusion the hypoxic augmentation, which is mediated by a nitric oxide‐dependent pathway in the endothelium, is facilitated.

5. In vivo studies revealed hyperconstriction of reperfused arteries in response to hypoxaemia (PO2= 30‐40 mmHg) and administration of either serotonin or ergonovine.

6. Twelve weeks following reperfusion injury, coronary arteries still exhibited augmented endothelium‐dependent hypoxic augmentations in vitro, which were inhibited by NG‐monomethyl‐L‐arginine.

7. Furthermore, resting coronary segments with endothelium displayed hypoxia‐induced contractions that could not be inhibited by indomethacin, the lipoxygenase inhibitor AA861, superoxide dismutase plus catalase, deferoxamine, ouabain, or NG‐monomethyl‐L‐arginine.

8. These endothelium‐dependent hypoxic response may play a role in the pathogenesis of hyperconstriction (vasospasm) following coronary reperfusion.
EFFECTS OF TETRANDRINE AND CLOSELY RELATED BIS‐BENZYLISOQUINOLINE DERIVATIVES ON CYTOSOLIC Ca2+ IN HUMAN LEUKAEMIC HL‐60 CELLS: A STRUCTURE‐ACTIVITY RELATIONSHIP STUDY
Authors: Leung Yuk‐Man , Berdik Mariana , Kwan Chiu‐Yin , Loh Tatt‐Tuck
Published: June 2007

1. Previously it has been shown that tetrandrine (TET), a bis‐benzylisoquinoline alkaloid, isolated from a Chinese herb Stephania tetrandra, can block non‐voltage‐operated Ca2+ entry activated by intracellular Ca2+ store depletion induced by thapsigargin (TSG) and can release intracellular Ca2+ in HL‐60 cells. The present study attempted to identify the chemical group(s) of the TET molecule responsible for these dual effects. The effects of TET and its closely related analogues, hernandezine (HER) and berbamine (BER), on Ca2+ entry and Ca2+ release were compared in fura‐2‐loaded HL‐60 cells.

2. Berbamine was much less potent (IC50= 200 μmol/L) than TET and HER (both IC50 values = 25 μmol/L) in inhibiting Ca2+ entry activated by TSG. Furthermore, at 100 μmol/L, BER was much less effective than TET and HER in suppressing TSG‐induced Mn2+ entry. At 30‐100 μmol/L, BER was significantly less effective than both TET and HER in causing Ca2+ release from internal stores. However, only BER was able to cause store depletion‐activated Ca2+ entry (or the so‐called ‘capacitative Ca2+ entry') upon Ca2+ readmission.

3. Taken together, the data from this structure‐activity relationship study reveal that the‐OCH3 group of one particular benzene ring of TET, which distinguishes TET from BER, in part produces the dual pharmacological actions of TET.
EFFECTS OF FULLER'S EARTH AND ACTIVATED CHARCOAL ON ORAL ABSORPTION OF PARAQUAT IN RABBITS
Authors: Idid SZ , Lee CY
Published: June 2007

1. Thirty male rabbits of local strain (weighing 1.5‐2kg) were divided into five groups. Four groups were treated with an oral dose of paraquat, which was followed by either Fuller's Earth or activated charcoal 0.5 or 2.0 h later. The remaining group acted as the control group and was treated only with an oral dose of paraquat. The dose of paraquant was 20.0 mg/kg given in a concentration of 20.0 mg/mL.

2. Both adsorbents were administered in 15mL normal saline as a 30% slurry. Blood was sampled from the ear vein 0.5, 1, 2, 4, 8 and 24 h after the administration of paraquat.

3. Paraquat concentration was determined spectophotometrically at 600 nm by comparing against a standard curve of paraquat obtained by the addition of standard paraquat into normal rabbit serum and extracting interfering substances with ether.

4. The results of the present study show that either adsorbent can bring down the serum paraquat level. There was no significant difference found in the effectiveness of either adsorbent.

5. It is concluded that the administration of an adsorbent as early as possible will help in the reduction of paraquat absorption from the gastrointestinal tract.

6. Activated charcoal is still effective in lowering serum paraquat concentration when given more than 1 h after ingestion of paraquat.
CHANGES IN RENAL RENIN GENE EXPRESSION IN FETAL SHEEP†
Authors: Zhang David Yanling , Lumbers Eugenie R. , Simonetta Giuseppe
Published: June 2007

1. Renin gene expression was investigated in kidneys from 13 foetal and four adult sheep.

2. The levels of renal renin and mRNA in foetuses were greater than those in adult sheep (P < 0.001).

3. There was no significant difference in renin mRNA levels between foetuses aged 91 and 134 days (term 150 days).

4. The levels of renin gene expression were higher (178±5 units; P < 0.001) in foetuses at 142 days than levels in 91 (144±4 units) and 134 days old foetuses (146±6 units).

5. It is concluded that the high level of renin gene expression in the foetal kidney in responsible for the high levels of renin in the foetal circulation.
SILENT AFFERENTS: A SEPARATE CLASS OF PRIMARY AFFERENTS?
Authors: Michaelis M. , Häbler H‐J , Jänig W.
Published: June 2007

1. In recent years, fine sensory nerve fibres have been detected that are not excited by physiological stimuli, even at potentially tissue damaging intensities. These silent afferents are known to supply knee joint, skin and viscera; in the last case, silent afferents seem to be particularly numerous.

2. When an artificial inflammation is induced, many silent afferents develop spike activity, others remain quiescent. Silent afferents that do respond probably have a nociceptive sensory function. Under inflammatory conditions some silent afferents are sensitized to physiological stimuli, others are probably chemospecific.

3. Orthodromic activity in silent afferents may sum spatially and temporally in second order neurons with other nociceptive information and may thereby contribute to different pain states. Furthermore, there is evidence that the activation of chemospecific silent afferents may lead to sensitization of nociceptive dorsal horn neurons.

4. Some silent afferents probably contain neuropeptides that may be liberated under pathophysiological conditions, such as inflammation.

5. Whether certain pathological states can be exclusively attributed to the activation of silent afferents or whether silent afferents sustain the functions of ‘conventional’ nociceptors remains to be clarified.
VALIDATION OF A SUBENDOCARDIAL ISCHAEMIC SHEEP MODEL BY INTRACORONARY FLUORESCENT MICROSPHERES
Authors: Li DS , Yong AC , Kilpatrick D.
Published: June 2007

1. We evaluated the use of non‐radioactive fluorescent‐labelled microspheres (FM) for the measurement of regional myocardial blood flow (RMBF) in an ischaemic sheep model.

2. Injection of FM directly into the coronary artery was compared with left atrial injection. There was a good correlation in the measurement of RMBF between these two injection methods (r = 0.92; n= 107 data points). Injection into the coronary artery requires less FM (one twentieth of that required by atrial injection) and is more economical.

3. The use of a fluorescent technique without filtering myocardial tissue was investigated. Calibration curves from the fluorescence plus myocardial tissue samples were similar to those of the pure fluorescence samples and both showed a linear relationship between fluorescent intensity and the number of microspheres (r > 0.97). These results indicate that the extraction of six fluorescent dyes (blue‐green, yellow‐green, green, orange, red and crimson) directly from the aqueous solution using ethyl acetate is effective.

4. A subendocardial ischaemic model was produced by partially occluding the circumflex artery (CxA) with concomitant left atrium (LA) pacing. During ischaemia, the endocardium/epicardium (Endo/Epi) flow ratios in the ischaemic area changed from 1.04 ± 0.12 to 0.47 ± 0.17 (P < 0.05; CxA injection) and from 1.08 ± 0.12 to 0.51 ± 0.05 (P < 0.05; LA injection). The ratio in the non‐ischaemic area remained unchanged (1.12 ± 0.26 to 1.01 ± 0.22; not significant).

5. RMBF calculation using coronary inflow as the reference flow was also compared with that using the traditional method. We found that, in this study in which a non‐filtering technique was applied, using coronary inflow as the reference flow was superior to the conventional distal sampling method.
TACHYKININ RECEPTORS AND NON‐CHOLINERGIC BRONCHOCONSTRICTION IN THE ANAESTHETIZED GUINEA‐PIG
Authors: Yuan Liqun , Burcher Elizabeth , Nail Bruce
Published: June 2007

1. Bronchoconstriction can be evoked by electrical stimulation of the vagus nerves in the presence of atropine. We have used novel, highly selective tachykinin receptor antagonists, together with a procedure for on‐line, breath‐by‐breath analysis of total lung resistance (Rl, subtractor method) and dynamic lung compliance (Cdyn), to investigate the role of tachykinins in this response in anaesthetized, paralysed guinea‐pigs.

2. In the presence of 1 mg/kg phosphoramidon (a neutral endopeptidase inhibitor), CP 96345 (the non‐peptide NK1 selective antagonist) at 200 nmol/kg had no effect on the increase in Rl caused by vagal stimulation, but significantly inhibited the associated decrease in Cdyn.

3. The NK2 selective antagonist, MDL 29913 (1 μmol/kg), significantly antagonized the changes in both Rl and Cdyn. In the absence of phosphoramidon, MDL 29913 again significantly inhibited the changes in Rl and Cdyn, although CP 96345 no longer had any effect.

4. The non‐peptide NK2 selective antagonist, SR 48968 (100 nmol/kg), also effectively inhibited the responses to vagal stimulation and was more potent than MDL 29913.

5. These results emphasize the importance of the NK2 receptor system in mediating non‐cholinergic bronchoconstriction evoked by vagal stimulation in the guinea‐pig.
CHANGES IN BLOOD AND RED CELL VOLUME IN THE NEONATAL LAMB AND THE EFFECT OF INSULIN‐LIKE GROWTH FACTOR I
Authors: Moritz Karen M. , Owens Phillip C. , Wintour E Marelyn
Published: June 2007

1. Blood volume was measured weekly using [51Cr]‐labelled red cells in 10 lambs from 3 to 10 weeks of age. Red cell and plasma volumes were calculated using the measured blood volume and haematocrit. Other parameters, including plasma erythropoietin, urea, creatinine and glucose, were measured twice weekly. The results were compared to a group of five lambs that received an infusion of insulin‐like growth factor I (IGF‐I).

2. In control lambs, plasma volume increased linearly by 47 ± 7 mL/week over the experimental period. Red cell volume only increased by 10 ± 2 mL/week during weeks 3–7, but then increased by 25 ± 2 mL/week over weeks 7–10. Haematocrit declined from 28.0 ± 1.6 to 24.7 ± 1.7% over weeks 3–7 and then increased to 30.7 ± 1.1% by week 10.

3. In 10 control lambs infused for 8 days (starting at 22–26 days of age) with 10 mmol/L HCl, there was a decrease in plasma IGF‐I concentrations, 3 days after the start of infusion. In five lambs infused for 8 days with IGF‐I (6 μg/kg per h) plasma IGF‐I concentration was maintained significantly (P < 0.01) higher than that of the controls.

4. There was no significant difference in haematocrit, red cell or plasma volumes between the treatment groups and no reticulocytosis was observed. Plasma erythropoietin concentrations did not change over the infusion period in either group.

5. Serum urea decreased significantly in the IGF‐I infused group but serum creatinine did not change in either group during the infusion period. In both the groups, there was a significant decrease in glucose, urea and creatinine over weeks 3–10 after birth. There was no difference in growth rates between the two groups.

6. Thus, it appears that the observed changes in haematocrit are due to a constant increase in plasma volume with varying rates of red cell volume increases.

7. IGF‐I infused at a dose that maintains physiological concentrations and alters protein metabolism does not result in increased erythropoietin or erythropoiesis during the neonatal period of the lamb.
CNS PATHWAYS MEDIATING CARDIOVASCULAR REGULATION OF VASOPRESSIN
Authors: Renaud Leo P.
Published: June 2007

1. The release of vasopressin from the neurohypophysial terminals of hypothalamic magnocellular neurosecretory neurons is subject to regulation by peripheral baroreceptors, cardiopulmonary volume receptors and circulating angiotensin II. Information from these sources is transmitted through different pathways to achieve different influences on the excitability of the vasopressin‐secreting cells.

2. A brief increase in arterial pressure, sufficient to activate baroreceptors, is associated with a transient and selective GABAergic inhibition of these neurosecretory neurons, achieved through a multisynaptic pathway that involves ascending catecholaminergic fibres and neurons in the diagonal band of Broca. A decrease in arterial pressure activates peripheral low volume receptors and initiating neural inputs that result in an increase in the excitability of vasopressin‐secreting neurons, achieved via pathways that include direct projections from caudal ventrolateral medulla A1 neurons.

3. Hypotension also releases renal renin and leads to the formation of angiotensin II; binding of this hormone to AT1 receptors on subfornical organ neurons promotes activation of a central angiotensinergic input that evokes a predominantly excitatory effect on vasopressin neurons.
ROLE OF THE HYPOTHALAMIC PARAVENTRICULAR NUCLEUS IN CARDIOVASCULAR REGULATION
Authors: Blair Martha L. , Piekut Diane , Want Andrew , Olschowka John A.
Published: June 2007

1. The paraventricular hypothalamic nucleus (PVH) is a complex structure with both neuroendocrine and autonomic functions. It is a major source of vasopressin and the primary source of corticotropin‐releasing factor. In addition, parvicellular PVH neurons have reciprocal connections with brain‐stem autonomic centres and directly innervate sympathetic preganglionic neurons. Evidence is reviewed which indicates that in conscious rats PVH activation increases blood pressure, heart rate, renal nerve activity and plasma renin activity.

2. In conscious rats, a non‐hypotensive haemorrhage (13 mL/kg blood loss over 24 min) results in increased numbers of Fos‐immunoreactive cell nuclei within both magnocellular and parvicellular PVH neurons, including the ventral medial parvicellular regions known to contain neuronal projections to brainstem autonomic centres and spinal cord sympathetic preganglionic neurons.

3. Cell‐selective ibotenate lesions of the parvicellular PVH significantly blunt the corticosterone response but do not alter blood pressure, heart rate or plasma renin concentration response to non‐hypotensive or hypotensive haemorrhage. This and earlier studies indicate that, while the PVH is necessary for the corticosterone response and contributes to increased vasopressin release during blood loss, it does not play an important role in the sympathetic nervous system and renin‐angiotensin responses to hypovolaemia and hypotension.

4. There is evidence to indicate that the parvicellular PVH serves as a necessary relay for cardiovascular and renin responses to certain behavioural stressors. We propose that cardiovascular information relayed to parvicellular PVH autonomic regions may be used to modulate behavioural, rather than homeostatic, effects on haemodynamics and renin release.
ROLE OF THE DORSOMEDIAL HYPOTHALAMUS IN THE CARDIOVASCULAR RESPONSE TO STRESS
Authors: DiMicco Joseph A. , Stotz‐Potter Elizabeth H. , Monroe Amy J. , Morin S Michelle
Published: June 2007

1. Disinhibition of the dorsomedial hypothalamus (DMH) in rats by local microinjection of GABAA receptor antagonists evokes behavioural and physiological changes resembling those seen in acute experimental stress.

2. Conversely, similar microinjection of muscimol, a potent agonist at inhibitory GABAA receptors, virtually abolishes stress‐induced increases in heart rate and arterial pressure.

3. Blockade of excitatory amino acid (EAA) receptors in the DMH also attentuates stress‐induced cardiovascular changes and microinjection of kainate, AMPA or NMDA at low doses elicits cardiovascular effects resembling those seen in stress. Paradoxically, injection of higher doses of NMDA or of glutamate into this region has no consistent effect.

4. The cardiovascular effects of bicuculline methiodide, a GABAA receptor antagonist, as well as those of NMDA and/or kainate were assessed after identical injection into either the DMH, the paraventricular nucleus (PVN) or the area between the two nuclei in both anaesthetized and conscious rats. For each agent, a similar pattern was seen, with the largest increases in heart rate and arterial pressure occurring after injection into the DMH and the smallest changes resulting from injection into the PVN.

5. In a parallel study, bilateral microinjection of muscimol into the DMH dramatically reduced air stress‐induced cardiovascular changes; similar injection into the area of the PVN had no effect, while injection into the area between the nuclei produced an intermediate effect.

6. Our findings suggest that activation of neurons in the region of the DMH mediates stress‐induced cardiovascular changes and that the activity of these neurons may be determined by the balance of tone at inhibitory GABAA receptors and EAA receptors.
FOREBRAIN PATHWAYS AND THEIR BEHAVIOURAL INTERACTIONS WITH NEUROENDOCRINE AND CARDIOVASCULAR FUNCTION IN THE RAT
Authors: Bohus Béla , Koolhaas Jaap M. , Korte S Mechiel , Roozendaal Benno , Wiersma Anja
Published: June 2007

1. The forebrain is a major organizer of the complex behavioural, physiological and neuroendocrine responses to environmental challenges of a stressful nature.

2. Combined physiological and neuroanatomical studies suggest that a specific forebrain‐brain stem network, composed of connections between the central nucleus of the amygdala, the paraventricular nucleus of the hypothalamus, the mesencephalic cuneiform nucleus, the parabrachial nucleus and the dorsal motor nucleus of the vagus nerve, may be important for integrating behavioural and physiological responses.

3. Based on studies using bilateral electrolytic lesions of the central nucleus of the amygdala, it has become clear that the central nucleus of the amygdala is one of the key structures involved in unconditioned responses to inescapable footshock. These responses include freezing behaviour, tachycardia and the release of adrenaline, noradrenaline, prolactin and corticosterone. However, this nucleus is involved only in the freezing behaviour and bradycardiac responses to conditioned emotional stress or to social defeat.

4. Both peptidergic (corticotropin releasing hormone and vasopressin/oxytocin) and aminergic (noradrenaline and dopamine) mechanisms in the central amygdala are involved in the regulation of integrated behavioural, physiological and neuroendocrine stress responses. This is indicated by studies with an infusion of an agonist and/or antagonist of the peptides or neurotransmitters into the central amygdala of freely moving rats. Sympathetic cardiac control is intensified by corticotropin releasing hormone and oxytocin, probably by inhibiting vagal output. In contrast, vagal activity is facilitated by vasopressin, noradrenaline and dopamine.
A PROPOSED MECHANISM FOR THE CARDIOPROTECTIVE EFFECT OF OESTROGEN IN WOMEN: ENHANCED ENDOTHELIAL NITRIC OXIDE RELEASE DECREASES CORONARY ARTERY REACTIVITY
Authors: Wellman George C. , Brayden Joseph E. , Nelson Mark T.
Published: June 2007

1. During their reproductive years women have a much lower incidence of coronary heart disease than men of similar age. A cardioprotective effect of circulating oestrogen appears to be responsible for this decrease in cardiovascular mortality in women.

2. Oestrogen can enhance nitric oxide (NO) production by the vacular endothelium, possibly through enhanced production of the enzyme NO synthase.

3. Pressure‐induced constrictions in isolated coronary arteries from rats with physiological circulating levels of oestrogen are reduced compared to oestrogen‐deficient animals. This difference is abolished by endothelial removal or inhibition of NO synthase.

4. NO through stimulation of guanylyl cyclase increases levels of the cytosolic second messenger cyclic GMP (cGMP) which activates a cGMP‐dependent protein kinase in vascular smooth muscle cells.

5. Potassium currents through calcium‐activated channels in vascular smooth muscle cells are increased in response to NO or upon exposure to cGMP‐dependent protein kinase.

6. In rat coronary arteries dilations to NO are reduced by agents which inhibit calcium‐activated potassium channels. NO can also hyperpolarize this tissue, suggesting membrane potential changes are involved in the response to NO.

7. We propose that oestrogen increases NO production leading to more negative membrane potentials and decreased calcium entry in coronary vascular smooth muscle cells.
CORTICOSTEROIDS IN ESSENTIAL HYPERTENSION: MULTIPLE CANDIDATE LOCI AND PHENOTYPIC VARIATION
Authors: Connell JMC , Kenyon CJ , Ingram M. , Holloway C. , Jamieson A. , Panarelli M. , Inglis G. , Fraser R.
Published: June 2007

1. The role of genetically determined changes in adrenal steroid production, metabolism and action in the pathogenesis of cardiovascular disease in man is considered by studying three loci that are important in corticosteroid function.

2. Variation at the glucocorticoid receptor locus can be identified as a biallelic restriction fragment length polymorphism (Bcl1); subjects with contrasting genotypes show altered skin vasoconstrictor responses to topically applied budesonide without any significant change in leucocyte receptor binding characteristics.

3. In a case control study of patients with essential hypertension, we have shown evidence of reduced 11β‐hydroxysteroid dehydrogenase activity, with an elevated ratio of cortisol to cortisone metabolites in urine.

4. The genes encoding 11β‐hydroxylase and aldosterone synthase are highly homologous. Studies in the Milan hypertensive rat show variation at this locus, which may account for the increased steroid synthesis noted in the hypertensive strain; in man, a chimaeric gene comprising 5’ regulatory regions from 11β‐hydroxylase and 3’ coding sequence from aldosterone synthase accounts for the autosomal dominant condition Dexamethasone Suppressible Hyperaldosteronism. Variation in the precise location of the crossover site between the two genes does not account for the observed phenotypic heterogeneity in this condition.

5. Measurement of basal plasma steroid levels in subjects with essential hypertension show an increased ratio of 11‐deoxycortisol/cortisol, consistent with reduced activity of 11β‐hydroxylase in the zona fasciculata.

6. In summary, three loci involved in corticosteroid synthesis, metabolism and action can independently affect cardiovascular phenotypes; their roles in determining pathophysiological changes, including hypertension, remain to be studied.
ENDOTHELINS CONTRACT GUINEA‐PIG PULMONARY ARTERY AND ENHANCE ITS ADRENERGIC RESPONSE VIA ETA RECEPTORS
Authors: Matsuda H. , Kawaguchi A. , Uematsu M. , Ohmori F. , Nagata S. , Miyatake K.
Published: June 2007

1. This study has pharmacologically characterized endothelin (ET) receptor subtype(s) mediating contraction and enhancement of adrenergic contraction in guinea‐pig pulmonary artery. Isometric tension of the isolated endothelium‐denuded ring preparations was measured in the presence of indomethacin (10−5 mol/L) and NG‐nitro‐L‐arginine methyl ester (l‐NAME; 3X10−4 mol/L) to exclude a mechanism via endothelium, cyclo‐oxygenase‐generated eicosanoids and nitric oxide.

2. In the additional presence of tetrodotoxin (TTX; 3X10−7 mol/L), ET‐1 (10−11‐10−7 mol/L) concentration‐dependently contracted the preparations. The rank order of potency to contract the preparations among ET receptor agonists was ET‐1, sarafotoxin (STX) 6b>ET‐3>IRL 1620, STX 6c. BQ‐123 (7X10−7‐7X10−6 mol/L) concentration‐dependently shifted the concentration‐contraction curve for ET‐1 to the right in a parallel manner. Pretreatment with STX 6c (3X10−7 mol/L for 30 min) did not significantly desensitize contractions to ET‐1, ET‐3 or IRL 1620 (P>0.05; t‐test, 10 d. f.).

3. ET‐1 (10−10‐10−9 mol/L) and STX 6b (10−9‐10−8 mol/L) significantly enhanced the electrical field stimulation‐induced contraction in a BQ‐123‐sensitive manner (P<0.05; t‐test, 24–38 d.f.), while ET‐3 (10−11‐10−8 mol/L) and STX 6c (10−11‐10−7 mol/L) did not affect contractions. ET‐1 (10−11 mol/L) significantly enhanced contractions to exogenous nor‐adrenaline in the presence of TTX (3X10−7 mol/L) (P<0.05; t‐test, 16 d.f.).

4. These data indicate that the BQ‐123‐sensitive ETA receptor mediates both contraction and enhancement of adrenergic contractions in the guinea‐pig pulmonary artery.
INTERSTITIAL ADENOSINE AND FUNCTION IN RAT HEART IN VIVO: EFFECTS OF ADRENALINE AND 8‐CYCLOPENTYL‐1,3‐DIMETHYLXANTHINE
Authors: Headrick John P
Published: June 2007

1. Left ventricular interstitial adenosine and cardiac function were studied in open chest rats during adrenaline stimulation and P1‐purinoceptor antagonism with 8‐cyclopentyl‐1,3‐dimethylxanthine (8‐CPT).

2. Cardiac microdialysate adenosine concentration was 0.10±0.01 μmol/L (n= 24) under basal conditions, giving an estimated interstitial adenosine concentration of 0.27 μmol/L. Stimulation with 3.2 and 8.0 μg/kg per min adrenaline increased the rate‐pressure product (heart rate X systolic blood pressure) by 72 and 157%, respectively, and increased dialysate adenosine to 0.26±0.04 and 0.65±0.11 μmol/L (n= 12), respectively (interstitial concentrations of approximately 0.70 and 1.76 μmol/L).

3. Treatment with 60 μg/kg per min 8‐CPT did not alter basal adenosine concentrations, but potentiated elevations in dialysate adenosine during infusion of 3.2 and 8.0 μg/kg per min adrenaline to 0.54±0.10 and 1.30±0.22 μmol/L, respectively (n= 12). Basal function and the response to 8.0 μg/kg per min adrenaline were unaltered by 8‐CPT, whereas elevations in heart rate and rate‐pressure product during stimulation with 3.2 μg/kg per min adrenaline were enhanced by 8‐CPT (by up to 30%).

4. Studies in isolated hearts confirmed the inhibitory potency of 8‐CPT at A1vs A2 P1‐purinoceptors (e.g. pKB of 7.7±0.2 and 6.4±0.1 for 5′‐N‐ethyl carboxamidoadenosine‐mediated bradycardia and vasodilatation, respectively; n= 6). Studies in intact animals verified effective A1 blockade by 60 μg/kg per min 8‐CPT, but also revealed some inhibition of A2‐mediated responses.

5. In conclusion, the data show that cardiac interstitial adenosine levels exist within a physiologically active range in vivo and increase dose‐dependently during graded adrenaline stimulation. Adenosine receptor antagonism enhances elevations in interstitial adenosine and modifies functional responses to moderate, but not high, doses of adrenaline. Whether 8‐CPT‐dependent elevations in interstitial adenosine are due to A1 inhibition vs inhibition of A2‐mediated vasodilatation requires further investigation.
NITRIC OXIDE INHIBITION IN AN OVINE MODEL OF HEART FAILURE
Authors: Rademaker Miriam Tessa , Fitzpatrick Michael Andrew , Richards Arthur Mark , Nicholls Michael Gary , Charles Christopher John , Frampton Christopher Miles , Ikram Hamid
Published: June 2007

1. The role of nitric oxide (NO) in congestive heart failure was investigated by studying the acute haemodynamic, hormonal and renal effects of NG‐monomethyl‐l‐arginine (l‐NMMA), a nitric oxide inhibitor, given as incremental bolus doses in six sheep before (normal) and after induction of heart failure (HF) by rapid left ventricular pacing (LVP).

2. l‐NMMA caused significant initial dose‐dependent rises in left ventricular systolic pressure, mean arterial pressure (MAP), peripheral resistance (PR) and left atrial pressure and declines in cardiac output in both normal and HF states (maximum response in 2–6 min). These responses were all but abolished when l‐arginine was given concurrently with l‐NMMA. The dose‐response curve for the l‐NMMA‐induced rise in MAP was shifted to the right following LVP (P<0.05), which is consistent with previous observations of blunted NO synthase activity in HF. A subsequent decline in MAP and PR to below prebolus levels was observed 30–60 min after l‐NMMA administration in the paced state. No significant hormonal or renal effects were observed.

3. In conclusion, the present study confirms the important haemodynamic role played by endogenous NO in the normal state and demonstrates a blunted pressor response to NO inhibition in this model of heart failure.
STRUCTURE‐ACTIVITY RELATIONSHIPS FOR 4‐ANILINOQUINAZOLINES AS POTENT INHIBITORS AT THE ATP BINDING SITE OF THE EPIDERMAL GROWTH FACTOR RECEPTOR IN VITRO
Authors: Denny William A , Rewcastle Gordon W , Bridges Alexander J , Fry David W , Kraker Alan J
Published: June 2007

1. Structure‐activity relationships are described for the inhibition of the tyrosine kinase activity (phosphorylation of a fragment of phospholipase Cg1) of the epidermal growth factor receptor (EGFR) by 4‐anilinoquinazolines. These compounds are competitive inhibitors at the ATP binding site.

2. The preferred side chain is anilino‐, substituted at the 3‐position with small lipophilic groups. The quinazoline moiety is absolutely required for activity, but substituents on the quinazoline greatly modulate potency, with electron‐donating groups favoured. The most potent analogue, the 6,7‐dimethoxy derivative (compound 20), has an IC50 of 29 pmol/L and a very high selectivity for the EGFR over other tyrosine kinase enzymes.

3. The present study shows that it is possible to identify small molecules that are very potent, yet highly selective, inhibitors of a single component of the growth signal transduction pathway in cells.
EFFECT OF ATRIAL NATRIURETIC FACTOR ON CORTICOTROPHIN‐RELEASING HORMONE‐INDUCED ADRENOCORTICOTROPHIN RELEASE IN THE MATURE OVINE FOETUS
Authors: McFarlane AC , Wintour EM
Published: June 2007

1. Atrial natriuretic factor (ANF) and its analogues have been shown previously to inhibit corticotrophin‐releasing hormone (CRH)‐induced adrenocorticotrophin (ACTH) release, both in vivo and in vitro, and it has been suggested that ANF may be a, or the, physiological ACTH‐inhibitory factor. To determine whether ANF is relevant in the regulation of ACTH secretion in the ovine foetus, the present study examines the effect of ANF on CRH‐stimulated ACTH release in the mature ovine foetus.

2. Five chronically cannulated foetuses, studied between 129 and 140 days of gestation (term 145–150 days), received intraarterial infusions of ovine CRH (4 μg/h) 120 min after the start of a sustained infusion of human ANF5–28 (10 μg/h) or saline (1.2 mL/h). Appropriate control experiments were performed, with foetuses receiving ANF or saline infusion only. CRH, ACTH, ANF and cortisol levels were measured by sensitive and specific radioimmunoassays. Each animal received all four treatments, with the order being randomized and 2–3 days being allowed between experiments.

3. It was found that pretreatment (120 min) with ANF5–28 (at levels devoid of significant cardiovascular actions) had no effect on mean basal or peak ACTH and cortisol levels during CRH infusion. Given the current experimental parameters, these results suggest that ANF does not acutely modulate basal or CRH‐stimulated ACTH and cortisol release in the mature ovine foetus.
EFFECTS OF HISTAMINE AND 5‐HYDROXYTRYPTAMINE ON THE GROWTH RATE OF XENOGRAFTED HUMAN BRONCHOGENIC CARCINOMAS
Authors: Sheehan Peter FJ , Baker Timothy , Tutton Peter JM , Barkla David H
Published: June 2007

1. The influence of histamine and 5‐hydroxytryptamine (5‐HT) antagonists and agonists on the volume doubling times (Td) of human bronchogenic carcinomas propagated as s. c. xenografts in immunosuppressed mice was examined.

2. The H2‐receptor antagonists, cimetidine and ranitidine, increased Td.

3. Treatment with the H2‐receptor agonist, 4‐methyl histamine, had no effect on Td.

4. Co‐administration of 4‐methyl histamine and cimetidine abolished the effects of cimetidine.

5. The 5‐HT2‐receptor antagonists, cinanserin and ketanserin, both increased Td.

6. Treatment with the 5‐HT1/2‐receptor agonist quipazine (0.1 mg/kg, reflecting 5‐HT2 agonist activity) decreased Td, while a higher dose (10.0mg/kg) had no effect.

7. The 5‐HT1/2‐receptor antagonist, methiothepin, decreased Td.

8. The 5‐HT uptake inhibitor, fluoxetine, increased Td in one tumour line but not in another, while the 5‐HT releaser/depletor, fenfluramine, increased Td.

9. Histamine may stimulate tumour growth through the histamine H2‐receptor, while the dominant effect of 5‐HT is 5‐HT1‐receptor inhibition.

10. Tumour growth in some bronchogenic carcinomas may involve 5‐HT uptake mechanisms.
ANTI‐OBESITY AND ANTI‐DIABETIC EFFECTS OF MAZINDOL IN YELLOW KK MICE: ITS ACTIVATING EFFECT ON BROWN ADIPOSE TISSUE THERMOGENESIS
Authors: Yoshida Toshihide , Umekawa Tsunekazu , Wakabayashi Yasuo , Yoshimoto Kanji , Sakane Naoki , Kondo Motoharu
Published: June 2007

1. The anti‐obesity and anti‐diabetic effects of mazindol were evaluated in obese diabetic yellow KK mice and C57B1 control mice.

2. The study compound was fed through a gastric tube at a rate of 1 or 2 mg/kg per day (0.01 mol/L HC1 as control) for 2 weeks. The following parameters were compared in treated and control animals: bodyweight, food intake, white adipose tissue (WAT) weight, brown adipose tissue (BAT) weight and its thermogenesis, noradrenaline (NA) turnover, blood glucose and serum insulin levels and glucose transporter 4 (GLUT4).

3. Furthermore, bodyweight loss of mice pair‐fed the same amount of food as the mazindol‐treated mice for 2 weeks was measured.

4. Mazindol significantly decreased food intake and significantly increased guanosine‐5′‐diphosphate‐binding in BAT mitochondria and NA turnover in BAT in both yellow KK and C57B1 groups. The amounts of WAT in subcutaneous, mesenteric and retroperitoneal regions and bodyweights were significantly decreased in both groups. Bodyweight loss in mice pair fed with the mazindol‐treated groups was approximately 70% compared with that in the mazindol‐treated groups. Furthermore, mazindol decreased the levels of blood glucose and serum insulin during the glucose overloading test in yellow KK mice, but it did not influence the GLUT4 protein concentration in WAT and muscle.

5. These observations suggest that mazindol possesses both an anti‐obesity action, due to the inhibition of appetite as well as the activation of BAT thermogenesis via increased NA turnover in BAT, and an anti‐diabetic action. Consequently, mazindol may be useful for the treatment of obesity as well as non‐insulin‐dependent diabetes mellitus in obese persons.