bluuebunny/crossref_metadata_2025 huggingface dataset:
GLYCINE RECEPTORS: WHAT GETS IN AND WHY?
Authors: Barry Peter H , Schofield Peter R , Moorhouse Andrew J
Published: March 2003

1. The glycine receptor channel (GlyR), a member of the ligand‐gated ion channel superfamily, shares many similar permeation properties with the GABAA receptor channel.

2. The GlyR is anion permeable, with PK/PCl < 0.05, has a 5–6 Å minimum pore diameter and a permeation selectivity sequence dominated by hydration energies.

3. The channels, which display multiple subconductance states, can be multiply occupied.

4. Two positive arginine rings at the ends of the pore region may contribute to the anion selectivity of the GlyR.

5. Mutation of the extracellular charged arginine ring can impair channel function by decreasing the sensitivity of glycine activation, reducing channel conductance, shifting the normal multi‐subconductance states to lower values and by decoupling the link between ligand binding and channel gating.

6. These and other site‐directed mutagenesis studies of recombinant GlyR, together with studies of native GlyR, are providing further insights into what controls gating and ion permeation and selectivity through this channel.
LOW‐DOSE NITRO‐L‐ARGININE ADMINISTRATION IN BABOON (PAPIO HAMADRYAS) PREGNANCY
Authors: Hennessy Annemarie , Gillin Adrian G , Duggin Geoffrey G , Horvath John S , Tiller David J
Published: March 2003

1. The purpose of the present study was to examine the effect of nitric oxide (NO) inhibition on mean arterial pressure (MAP), endothelin (ET) and the renin–aldosterone system in pregnancy in the non‐human primate (baboon).

2. Twenty pregnant baboons (Papio hamadryas) were examined prospectively after the administration of an oral NO inhibitor in different phases of pregnancy. Haemodynamic responses to NO inhibition, evidence of pre‐eclampsia and the renin–aldosterone system were examined under anaesthesia.

3. Oral NL‐nitro‐
L‐arginine (NOLA; 5 or 10 mg/kg) was given for 1 week in early (6–8 weeks gestaton), middle (14–16 weeks gestation) and late (22–24 weeks gestation) pregnancy and while non‐pregnant. Mean arterial pressure, heart rate, haematology, biochemistry, ET, plasma renin activity (PRA) and aldosterone were measured. Foetal effects of NOLA were also examined by ultrasound and neonatal measurements.

4. Nitric oxide inhibition led to an increase in MAP in non‐pregnant animals (9 mmHg) and in middle and later pregnancy (6 and 7 mmHg, respectively). Mean arterial pressure in early pregnancy was not affected. A reduction in PRA occurred after NO inhibition in all stages of pregnancy. Significant proteinuria occurred only in late pregnancy.

5. Nitric oxide is involved in the maintenance of lower blood pressure in late pregnancy and inhibition leads to an increase in blood pressure and proteinuria in the baboon. Nitric oxide insufficiency may contribute to the clinical manifestations of human pre‐eclampsia. Nitric oxide was not involved in the normal vasodilation of early primate pregnancy.
CROSS‐OVER COMPARISON OF NIFEDIPINE OROS® AND FELODIPINE EXTENDED RELEASE WITH BLIND 24 H AMBULATORY BLOOD PRESSURE ASSESSMENTS
Authors: Taverner D , Marley J , Tonkin Al
Published: March 2003

1. The aim of the present study was to compare the efficacy of nifedipine Oros® and felodipine extended release (ER) in controlling 24 h ambulatory blood pressures (ABP) in hypertensive patients.

2. The study was a randomized cross‐over design with a 2 week open placebo run‐in phase and two observer‐blind treatment periods.

3. Subjects were males and females, aged between 18 and 65 years, suffering from mild to moderate essential hypertension with a sitting mean diastolic blood pressure (DBP) within the range of 95–114 mmHg. Twenty‐three subjects were randomized to treatment; 15 patients completed the study.

4. Treatment intervention was 2 weeks of placebo followed by either 30 mg nifedipine OROS once daily or 5 mg felodipine ER once daily for 6 weeks, which was titrated up to 60 mg nifedipine OROS daily or 10 mg felodipine ER daily after 2 weeks of treatment on the lower doses if the DBP was > 90 mmHg. The main outcome measure was 24 h ABP after 6 weeks of active treatment, evaluated by an independent observer blinded as to treatment allocation.

5. Compared with placebo, mean (±SD) 24 h DBP was reduced by 6.2±6.8 and 5.2±5.1 mmHg after nifedipine and felodipine, respectively. The 24 h mean systolic blood pressure (SBP) fell by 11.8±10.9 and 10.1±8.2 mmHg for nifedipine and felodipine, respectively, compared with placebo. There were no significant differences between the two active treatments in the reduction of DBP or SBP during the 24 h period, daytime or night‐time.

6. Similar antihypertensive effects are achieved with nifedipine Oros® and felodipine ER when doses are individually titrated, with no significant differences between the two treatments.
ROLE OF ACTION POTENTIAL SHORTENING IN THE PREVENTION OF ARRHYTHMIAS IN CANINE CARDIAC TISSUE
Authors: Mull Kawonia P , Debnam Qadriyyah , Kabir Syeda M , Bhattacharyya Mohit Lal
Published: March 2003

1. The effects of the K+ channel opener diazoxide and the oxime‐containing Ca2+ and K+ channel blocker salicylaldoxime were tested in canine cardiac Purkinje tissue.

2. Both drugs shortened action potential duration (APD). For salicylaldoxime (0.1–1.0 mmol/L), the reductions in APD were statistically significant at the 25% level of repolarization (APD25) for 0.1 mmol/L (P < 0.05, n = 14) and 0.5 and 1.0 mmol/L (P < 0.01, n = 6), at the 50% level of repolarization (APD50) for 0.1 mmol/L (P < 0.05, n = 14) and 0.5 and 1.0 mmol/L (P < 0.01, n = 6) and at the 90% level of repolarization (APD90) for 0.5 and 1.0 mmol/L (P < 0.01, n = 6). In contrast, diazoxide (0.05–0.1 mmol/L) significantly shortened APD at all levels of repolarizations, with the APD50 and APD90 reduced most significantly (P < 0.01, n = 6) for higher concentrations of the drug (0.07–0.1 mmol/L). Both drugs significantly reduced the force of contraction.

3. Diazoxide (10 experiments) was more potent in suppressing strophanthidin‐induced arrhythmias than salicylaldoxime (three of seven experiments). Salicylaldoxime reduced APD even further in the presence of diazoxide.

4. Although salicylaldoxime and diazoxide modulate different ion channels, it appears APD shortening may be a necessary, but insufficient, factor for the suppression of strophanthidin‐induced arrhythmias.
DOWN‐REGULATION BY BUCILLAMINE OF LAMINA PROPRIA LEUCOCYTES IN THE RAT COLITIS MODEL
Authors: Oshitani Nobuhide , Matsumoto Takayuki , Nakamura Shiro , Arakawa Tetsuo , Kitano Atsuo
Published: March 2003

1. The efficacy of bucillamine has been reported in various inflammatory models.

2. In the present study, the effects of 2 weeks administration of bucillamine on hapten‐induced experimental rat colitis were analysed. The gross morphological damage score was evaluated and the expression of CD4, CD8, CD11a, CD11b, CD25, CD54 and class II major histocompatibility complex (MHC) antigen was investigated by immunohistochemical methods.

3. Mean bodyweight was significantly increased in colitic rats given 750 μg bucillamine compared with colitic rats given vehicle (distilled water). Gross morphological damage was significantly less in colitic rats given 250 or 750 μg bucillamine compared with rats given vehicle.

4. Immunohistological studies revealed that CD4, CD11a, CD11b, CD54 and class II MHC antigen expression of infiltrating leucocytes was significantly lower in rat colonic mucosa treated with bucillamine.

5. From these findings, it appears that bucillamine may act through the down‐regulation of the activation of lamina propria leucocytes in hapten‐induced rat colitis.
XENOGENEIC INFECTIONS AND PUBLIC HEALTH
Authors: Chapman Louisa E
Published: March 2003

1. The scarcity of available human donor organs for use in allotransplantation has fuelled interest in xenotransplantation, the therapeutic use of living animal tissue in humans. The use of living animal tissue for therapeutic purposes in humans has raised concerns that xenotransplantation clinical trials may pose a presently unquantifiable but undeniable risk to public health.

2. Xenotransplantation has the potential to introduce new infections to the human community by infecting human recipients with agents that were not previously endemic in human populations (xenogeneic infections).

3. Manipulations intended to prevent xenograft rejection may also facilitate the transmission of agents that rarely or never infect humans under natural circumstances.

4. The US Food and Drug Administration (the government agency responsible for monitoring drug safety) has chosen to allow limited numbers of xenotransplantation clinical trials to proceed under carefully monitored conditions outlined in the Public Health Service (PHS) Guideline on Infectious Disease Issues in Xenotransplantation.

5. This PHS guideline particularly emphasizes the importance of pretransplantation screening and post‐transplantation surveillance for safety monitoring.

6. Laboratory based surveillance for endogenous retroviruses and other identifiable agents that cannot be removed from the xenograft can augment clinical surveillance.

7. Laboratory based studies of xenograft survivors increase our ability to quantify xenotransplant‐associated risks and, thereby, expand our capacity to make science‐based assessments of appropriate public policy.
Inhibitory Action Of Ambocarb On Voltage‐Operated Sodium Channels In Rat Isolated Hippocampal Pyramidal Neurons
Authors: Kopanitsa Maksim V , Krishtal Oleg A , Komissarov Igor V
Published: March 2003

1. A whole‐cell patch‐clamp study of the effects of ambocarb, a novel nootropic β‐carboline, on sodium currents in rat acutely isolated hippocampal pyramidal neurons was performed.

2. Ambocarb potently and reversibly suppressed sodium currents in a concentration range of 3–300 μmol/L. The amount of block was dependent on the holding potential, with half‐ maximal inhibition values being 26 and 94 μmol/L at –80 and –120 mV, respectively.

3. Ambocarb induced a hyperpolarizing shift in the steady state availability curve, which indicates an increase in the proportion of inactivated sodium channels. This action is presumably mediated by promoting the development of inactivation and slowing the recovery of sodium channels from inactivation.

4. Because many neuroprotective drugs were shown to inhibit sodium currents, down‐modulation of voltage‐operated sodium channels that complements the known positive interaction of ambocarb and other related β‐carbolines with GABAA receptors may provide a promising strategy in the treatment of brain disorders associated with trauma and ischaemia.
Renal Acid–Base And Sodium Handling In Hypoxia And Subsequent Mild Metabolic Acidosis In Foetal Sheep
Authors: Gibson Karen J , McMullen Julie R , Lumbers Eugenie R
Published: March 2003

1. To measure the renal contribution to acid–base homeostasis during hypoxia (not associated with hypercapnia) and in response to the subsequent mild metabolic acidosis and to determine the effects of this hypoxia on the renal handling of sodium, studies were performed in six chronically catheterized foetal sheep (129–138 days gestation) before, during and for 1 h after a 2 h period of hypoxia.

2. Hypoxia was induced in the conscious ewe by infusing nitrogen into the trachea. Foetal arterial oxygen tension fell to 12.0±0.6 mmHg (P < 0.001). Carbon dioxide tension fell during hypoxia (P < 0.001) and was still somewhat reduced in the recovery period (P < 0.005). Arterial pH fell progressively to 7.19±0.08 in the recovery period (P < 0.05). Plasma bicarbonate concentrations fell (P < 0.001) and lactate rose (P < 0.001).

3. Urinary pH and the excretion rates of bicarbonate, titratable acid, ammonium and net acid did not change during hypoxia. Ammonium excretion and, hence, generation of new bicarbonate increased in the recovery period (P < 0.05).

4. Renal sodium excretion progressively increased and was greatest after normoxia was restored (P < 0.05). This natriuresis was due to a fall in the reabsorption of sodium by the proximal tubule (P < 0.05). Proximal reabsorption of sodium was directly related to foetal pH (P < 0.0001) and bicarbonate reabsorption (P < 0.001).

5. It was concluded that: (i) the foetal kidneys began to contribute to the maintenance of acid–base balance within the first hour of recovery from a 2 h episode of hypocapnic hypoxia, even though the acidosis was relatively mild; and (ii) a reduction in bicarbonate reabsorption was probably the most important factor that limited sodium reabsorption by the renal tubule during this experiment.
T‐0162, A Novel Free Radical Scavenger, Reduces Myocardial Infarct Size In Rabbits
Authors: Yamashita Kazuya , Minatoguchi Shinya , Uno Yoshihiro , Kariya Tatsuya , Ohno Michiya , Arai Masazumi , Hashimoto Kazuaki , Nishida Yoshio , Nagashima Kenshi , Qiu Xinbin , Takemura Genzou , Suzuki Toshikazu , Fujiwara Takako , Fujiwara Hisayoshi
Published: March 2003

1. We investigated the effects of 1‐(3‐tert‐butyl‐2‐hydroxy‐ 5‐methoxyphenyl)‐3‐(3‐pyridylmethyl)urea hydrochloride (T‐0162), a novel low‐molecular weight free radical scavenger, on the generation of superoxide anions and hydroxyl radicals in vitro and in vivo and on myocardial infarct (MI) size in an in vivo model of MI in rabbits.

2. It was found that T‐0162 scavenged both superoxide anions and hydroxyl radicals in a concentration‐dependent manner in vitro.

3. In an in vivo rabbit model with 30 min coronary occlusion and 30 min reperfusion, T‐0162 scavenged hydroxyl radicals generated in the myocardium during reperfusion.

4. Anaesthetized open‐chest Japanese white male rabbits were subjected to 30 min coronary occlusion and 48 h reperfusion. The control group (n = 10) was infused with 10% lecithin solution for 220 min from 10 min before occlusion to 180 min after reperfusion. The pretreatment group (n = 10) was infused with T‐0162 dissolved in 10% lecithin solution for 220 min from 10 min before occlusion to 180 min after reperfusion at a rate of 400 μg/kg per min. The post‐treatment group (n = 10) was injected with an i.v. bolus of 10 mg/kg T‐0162 and was then infused with 400 μg/kg per min T‐0162 for 190 min from 10 min before reperfusion to 180 min after reperfusion. After 48 h reperfusion, infarct size was measured histologically and expressed as a percentage of area at risk (AAR).

5. There was no significant difference in haemodynamic parameters among the three groups throughout the experimental period. The per cent infarct size of the AAR in the T‐0162 groups (24.8±4.3 and 30.5±3.9% for pre‐ and post‐ treatment groups, respectively) was significantly reduced compared with control (44.7±4.1%; P < 0.05). There was no significant difference in the AAR among the three groups.

6. In conclusion, T‐0162 reduces MI size through the inhibition of reperfusion injury.
Krh‐594, A New Angiotensin At1 Receptor Antagonist, Ameliorates Nephropathy And Hyperlipidaemia In Diabetic Spontaneously Hypertensive Rats
Authors: Inada Yoichi , Murakami Makoto , Tazawa Shigeki , Akahane Masuo
Published: March 2003

1. We examined whether KRH‐594, a new angiotensin AT1 receptor antagonist, ameliorates the progression of diabetic nephropathy and hyperlipidaemia in streptozotocin (STZ)‐induced diabetic unilateral nephrectomized spontaneously hypertensive rats (DM‐1K‐SHR) or not.

2. The oral administration of KRH‐594 (3 and 10 mg/kg per day) and candesartan cilexetil (1 mg/kg per day) for 16 weeks significantly reduced systolic blood pressure, urinary albumin and urinary total protein in DM‐1K‐SHR.

3. In a histological study, KRH‐594 (3 and 10 mg/kg per day) and candesartan cilexetil (0.3 and 1 mg/kg per day) dose‐dependently improved glomerulosclerosis and the hyalin cast of tubules in DM‐1K‐SHR kidneys. Both KRH‐594 (10 mg/kg per day) and candesartan cilexetil (0.3 and 1 mg/kg per day) dose‐dependently inhibited cardiac hypertrophy.

4. KRH‐594 (3 and 10 mg/kg per day), but not candesartan cilexetil, dose‐dependently reduced the levels of triglyceride, total cholesterol and phospholipids in DM‐1K‐SHR.

5. These results suggest that KRH‐594 improves diabetic complications, such as nephropathy and hyperlipidaemia, with hypertension.
Relationship Of Cigarette Smoking With Blood Pressure, Serum Lipids And Lipoproteins In Young Japanese Women
Authors: Imamura Hiroyuki , Uchida Kazuhiro , Kobata Daikichi
Published: March 2003

1. The relationship of cigarette smoking with blood pressure and serum lipids and lipoproteins was studied in 1062 young Japanese women aged 20–39 years of age.

2. After adjusting for age, body mass index (BMI), alcohol intake and physical activity scores, the mean systolic and diastolic blood pressures (SBP and DBP, respectively) did not indicate dose‐dependent relationships with cigarette smoking. The largest significant mean differences in SBP (3.5%; P < 0.001), DBP (6.2%; P < 0.018), high‐density lipoprotein– cholesterol (HDL‐C; 13.2%; P < 0.005), ratio of total cholesterol to HDL‐C (13.9%; P < 0.022), triglycerides (TG; 24.1%; P < 0.001) and the logarithmic transformation of TG (log TG; 5.6%; P < 0.001) were found between non‐smokers and smokers.

3. When age, BMI, alcohol intake and physical activity scores were included in the forward step‐wise multiple regression analysis, there were negative relationships found for cigarette smoking and SBP and DBP and positive relationships for cigarette smoking and TG and log TG.

4. Although the results are somewhat variable, the present study shows that cigarette smoking is negatively associated with SBP and DBP and that there is an association between cigarette smoking and serum lipids and lipoproteins and that smoking has an unfavourable effect on these parameters in young Japanese women.
Deletion Polymorphism Of Angiotensin‐Converting Enzyme Gene Is Associated With Postprandial Hyperglycaemia In Individuals Undergoing General Check‐Up
Authors: Ohishi Mitsuru , Rakugi Hiromi , Miki Tetsuro , Katsuya Tomohiro , Okamura Atsunori , Kamide Kei , Nakata Yukiko , Takami Seiju , Ikegami Hiroshi , Yanagitani Yoshihiro , Tabuchi Yoshikatsu , Kumahara Yuichi , Higaki Jitsuo , Ogihara Toshio
Published: March 2003

1. Deletion polymorphism, DD, of the angiotensin‐converting enzyme (ACE) gene is reported to be related to cardiovascular disease, which is frequently based on insulin resistance.

2. To clarify the relationship between the ACE genotype DD and plasma glucose increases after an oral glucose load, we performed 75 g oral glucose tolerance test (OGTT) in 301 non‐diabetic men (age range 30–60 years) undergoing general check‐up.

3. Insertion/deletion (I/D) polymorphism of the ACE gene was explored using a polymerase chain reaction. The frequency of the II, ID and DD genotypes was 0.43, 0.43 and 0.14, respectively.

4. There were no differences in baseline clinical characteristics between subjects with each ACE genotype.

5. The mean (±SEM) plasma glucose level at 60 min of the OGTT was significantly higher in subjects with the DD genotype (170.8±6.9 mg/dL) than in subjects with either the II or ID genotype (mean value for two groups 156.6±2.7 mg/dL; P < 0.05). Moreover, the mean percentage change of plasma glucose after 60 min of the OGTT, a marker of plasma glucose increase, was significantly higher in individuals with the DD genotype than in individuals with either the II or ID genotypes.

6. In contrast, the mean fasting plasma glucose level, the plasma glucose level at 120 min, the glucose response area and the fasting insulin level were not different between individuals with the DD genotype and individuals with other genotypes.

7. In conclusion, subjects with the DD genotype showed transiently higher levels of plasma glucose after an oral glucose load than subjects with other genotypes. Further studies are required to determine whether the association between ACE genotype and postprandial hyperglycaemia influences the incidence of cardiovascular disease and diabetes mellitus.
Cellular Actions Of Opioids And Other Analgesics: Implications For Synergism In Pain Relief
Authors: Christie MacDonald J , Connor Mark , Vaughan Christopher W , Ingram Susan L , Bagley Elena E
Published: March 2003

1. μ‐Opioid receptor agonists mediate their central analgesic effects by actions on neurons within brain regions such as the mid‐brain periaqueductal grey (PAG). Within the PAG, μ‐opioid receptor‐mediated analgesia results from inhibition of GABAergic influences on output projection neurons. We have established that μ‐opioid receptor activation in the PAG causes a presynaptic inhibition of GABA release that is mediated by activation of a voltage‐dependent K+ channel via 12‐lipoxygenase (LOX) metabolites of arachidonic acid.

2. At a cellular level, μ‐opioid agonists have also been shown to open inwardly rectifying K+ channels, close voltage‐gated Ca2+ channels and presynaptically inhibit glutamatergic synaptic transmission in the PAG.

3. The μ‐opioid receptor‐mediated presynaptic inhibition of GABAergic transmission was abolished by phospholipase A2 inhibitors and non‐specific LOX and specific 12‐LOX inhibitors. Cyclo‐oxygenase (COX) and specific 5‐LOX inhibitors did not reduce the inhibitory effects of μ‐opioid agonists.

4. The opioid actions on GABAergic transmission were mimicked by arachidonic acid and 12‐LOX metabolites, but not 5‐LOX metabolites. The efficacy of μ‐opioids was enhanced synergistically by treatment of PAG neurons with inhibitors of the other major enzymes responsible for arachidonic acid metabolism, COX and 5‐LOX.

5. These results explain a previously described analgesic action of COX inhibitors in the central nervous system that was both independent of prostanoid release and inhibited by opioid receptor antagonists and they also explain the synergistic interaction of opioids with COX inhibitors. These findings also suggest new avenues for the development of centrally active analgesic agents involving combinations of lowered doses of opioids and specific 5‐LOX inhibitors.
Mitochondrial Function In Ischaemia And Reperfusion Of The Ageing Heart
Authors: Pepe Salvatore
Published: March 2003

1. In addition to Ca2+‐dependent mediation of excitation– contraction coupling during cardiac work and ATP hydrolysis, Ca2+ also stimulates the Krebs’ cycle and mitochondrial matrix dehydrogenases to maintain the nicotinamide adenine dinucleotide redox potential and ATP synthesis. Thus, the balance between energy demand and supply is maintained during increases in cardiac work by elevated cytosolic Ca2+ that is transmitted to the mitochondrial matrix via regulation of uniporter and antiporter pathways across the inner mitochondrial membrane.

2. Brief ischaemia perturbs Ca2+ homeostasis but mitochondrial buffering of Ca2+ permits maintained mitochondrial function. However, prolonged ischaemia and reperfusion causes Ca2+‘overload’ at supramicromolar levels. The onset of vicious cycles that abrogate contractile function and, ultimately, may cause irreversible cell injury involves: (i) loss of ionic homeostasis, energy production and anti‐oxidant enzyme activity; (ii) activation of phospholipases; and (iii) accumulation of free radicals, membrane lipid peroxidation products and protein adducts.

3. Increased permeability of the inner mitochondrial membrane to solutes occurs causing mitochondrial swelling, ‘proton leak’, reduced efficiency of the respiratory chain and uncoupling of oxidative phosphorylation. The opening of the mitochondrial permeability transition pore is potentiated by high mitochondrial Ca2+ and inducers, such as Pi, long‐chain acyl coenzyme (Co)A and oxygen free radicals. Opening of this channel depolarizes the mitochondrion and dissipates the H+ electrochemical gradient (ΔμH), preventing oxidative phosphorylation. Together with the release of cytochrome c and subsequent activation of caspase pathways, these events precede cell death.

4. Compared with younger counterparts, the senescent myocardium has a reduced capacity to recover from ischaemia and reperfusion. The consequent events described above are augmented in ageing. Elevated mitochondrial Ca2+ and increased dehydrogenase activation are linked to inefficient mitochondrial function and limited postischaemic recovery of contractile function.

5. Notably, a distinct decrease in the ratio of mitochondrial membrane ω‐3 to ω‐6 polyunsaturated fatty acids (PUFA) and a decrease in the mitochondrial phospholipid cardiolipin occurs in aged rat hearts. A diet rich in ω‐3 PUFA directly increases membrane ω‐3:ω‐6 PUFA and cardiolipin content and also facilitates improved tolerance of ischaemia and reperfusion. A major consequence of dietary ω‐3 PUFA may be the effect of altered mitochondrial Ca2+ flux and Ca2+‐dependent processes.
Effects Of Anaesthesia On Regional Coronary Control Mechanisms
Authors: Cottee DBF , Quail AW , Porges WL , Moore PG , White SW
Published: March 2003

1. The regional coronary circulation is under the control of local metabolic and myogenic factors, but is also influenced by autonomic systems, including sympathetic and parasympathetic nerves.

2. General anaesthetic agents influence not only local control through changes in metabolic demand, but also neural control through suppression of autonomic influence.

3. Anaesthetic agents have differing effects on reflex control systems, which are dependent on coronary territory and ventricular rate.

4. Effects of anaesthesia should be taken into account when interpreting results in anaesthetized models of coronary control.
Proceedings of the Australian Physiological and Pharmacological Society Symposium: Ion Channels EXPRESSION AND FUNCTION OF COLONIC EPITHELIAL KVLQT1 K+ CHANNELS
Authors: Kunzelmann K , Bleich M , Warth R , Levy‐Holzman R , Garty H , Schreiber R
Published: March 2003

1. KVLQT1 (KCNQ1) is a voltage‐gated K+ channel essential for repolarization of the heart action potential. Defects in ion channels have been demonstrated in cardiac arrhythmia. This channel is inhibited potently by the chromanol 293B. The same compound has been shown to block cAMP‐dependent electrolyte secretion in rat and human colon. Therefore, it was suggested that a K+ channel similar to KVLQT1 is expressed in the colonic epithelium.

2. In the present paper, expression of KVLQT1 and its function in colonic epithelial cells is described. Reverse transcription–polymerase chain reaction analysis of rat colonic mucosa demonstrated expression of KVLQT1 in both crypt cells and surface epithelium. When expressed in Xenopus oocytes, KVLQT1 induced a typical delayed activated K+ current.

3. As demonstrated, the channel activity could be further activated by increases in intracellular cAMP. These and other data support the concept that KVLQT1 is forming a component of the basolateral cAMP‐activated K+ conductance in the colonic epithelium.
Intrapituitary Interactions: Another Level Of Endocrine Regulation
Authors: Schwartz Jeff
Published: March 2003

1. Factors, produced within the anterior pituitary, act locally to influence many acute and developmental changes in neighbouring cells.

2. Broad spectra of factors and activities characterize these paracrine interactions.

3. Cleavage products of pro‐opiomelanocortin, other than those that act as systemic hormones, are produced by neonatal gonadotrophs and these peptides stimulate mitosis and differentiation of lactotrophs.

4. Activins and follistatins exert opposing effects on gonadotrophs. The stimulatory activity of activins is modulated extracellularly through protein–protein interactions with follistatin. Within gonadotrophs, the stimulatory activity of activins is self‐limiting through receptor‐mediated stimulatory and inhibitory signal transduction pathways.

5. During the oestrous cycle, the interactions between gonadotroph cells and epidermal growth factor (EGF), acting as a local signal, occur on multiple levels. Levels of expression of EGF receptors on cells vary as a function of the cycle, as do EGF‐induced changes in gene expression and proliferation of cells.
Pharmacology Of A Unique Adenosine Binding Site In Rat Brain Using A Selective Ligand
Authors: Yoshioka Kazuaki , Matsuda Akira , Nakata Hiroyasu
Published: March 2003

1. In order to further characterize the adenosine binding sites that we previously purified and termed P3 purinergic receptor‐like protein (P3LP), a reliable binding assay method was developed using [3H]‐5′‐N‐ethylcarboxamidoadenosine (NECA) as a radioligand and the newly developed high‐affinity selective ligand 9‐(6,7‐dideoxy‐β‐D‐allo‐hept‐5‐ynofuranosyl) adenine (HAK2701) as a selective displacer.

2. Using this assay method, it was found that rat brain membranes possess high‐ and low‐affinity [3H]‐NECA binding sites. The high‐affinity binding site showed KD and Bmax values of 19.7±2.5 nmol/L and 0.192±0.05 pmol/mg protein, respectively, and the KD value for the low‐affinity binding site was 4260±330 nmol/L. The KD value for the high‐affinity site agreed well with that of the [3H]‐NECA binding site determined with the partially purified P3LP preparation described previously.

3. The distribution of P3LP in rat tissues was determined using the [3H]‐NECA binding method described above. The highest level of P3LP was in the cerebellum followed by the olfactory bulb and the spinal cord.

4. The order of the affinity for various purinergic or related compounds to P3LP in rat brain preparations was also determined by the [3H]‐NECA binding method to be HAK2701 > NECA = adenosine 5′‐O‐(2‐thiodiphosphate) > cAMP = β,γ‐methyleneadenosine 5′‐triphosphate > diadenosine tetraphosphate > α,β‐methyleneadenosine 5′‐triphosphate > 5′‐deoxy‐5′‐methylthioadenosine > N6‐cyclopentyladenosine.

5. These studies reveal that the [3H]‐NECA binding assay in combination with HAK2701 is successful in the characterization of P3LP, especially the membrane‐bound form.
Maternal Environment Alters Renal Response To Angiotensin II In The Spontaneously Hypertensive Rat
Authors: Gouldsborough Ingrid , Ashton Nick
Published: March 2003

1. The level of hypertension displayed by the adult spontaneously hypertensive rat (SHR) may be reduced by 20–30 mmHg if SHR pups are cross‐fostered to a normotensive dam at birth (SHRX). The mechanisms involved are largely unknown, but may involve the kidney and the renin–angiotensin system (RAS) because renal responses to angiotensin (Ang) II are enhanced in the SHR and brief blockade of the RAS in the young rat permanently lowers blood pressure in the SHR. Accordingly, the aim of the present study was to investigate the effect of cross‐fostering on the renal response to AngII in the SHR.

2. Renal function was studied in anaesthetized 4‐week‐old SHR, cross‐fostered SHRX and control Wistar‐Kyoto (WKY) rats. Standard clearance methods were used to investigate the renal haemodynamic and tubular effects of AngII. The nitric oxide synthase (NOS) inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME) was coinfused in some experiments to abolish the counterbalancing effect of nitric oxide.

3. Angiotensin II induced a fall in glomerular filtration rate (GFR) in both SHR and SHRX, but not in WKY rats. This was accompanied by a significant reduction in sodium excretion by SHR but not SHRX pups. This effect appeared to be tubular in origin, because sodium clearance was comparable between the two strains after AngII, but fractional sodium excretion was significantly higher in the SHRX. Coinfusion of the NOS inhibitor L‐NAME had little further effect on sodium excretion in SHR and SHRX, but restored GFR in SHRX to levels comparable with those in WKY rats.

4. These data suggest that renal tubular sensitivity to AngII in the SHR can be altered during the early stages of postnatal development, which may contribute to the blood pressure‐ lowering effect of cross‐fostering in the SHR.
Circumventricular Organs: Gateways to the Brain Membrane Properties Of Subfornical Organ Neurons
Authors: Washburn David Ls , Ferguson Alastair V
Published: March 2003

1. The subfornical organ (SFO) is a forebrain circumventricular structure that plays an integral role in the regulation of fluid balance by acting as the interface between the circulation and the central nervous system. Thus, changes in the activity of SFO neurons can have significant effects on key regulatory loci involved in autonomic control, such as the hypothalamus and medulla.

2. Circulating messengers that affect SFO neurons do so through receptor‐mediated regulation of the intrinsic ionic conductances expressed by SFO neurons. It is through the coordinated interaction of the complement of voltage‐gated ion channels that SFO neurons are able to produce unique firing patterns and respond specifically to such a wide range of diverse extracellular messengers.
Circumventricular Organs: Gateways to the BrainApproaches For Gene Delivery To The Subfornical Organ And Magnocellular Neurons
Authors: Vasquez Elisardo C , Meyrelles Silvana S , Chapleau Mark W , Johnson Alan Kim
Published: March 2003

1. The subfornical organ (SFO), the magnocellular neurons in supraoptic (SON) and paraventricular (PVN) nuclei and the neurohypophysis (NH) constitute an important neuroendocrine axis for the maintenance of cardiovascular and body fluid homeostasis in mammals. The SFO lacks a blood–brain barrier and is an important target for the effects of circulating angiotensin II on thirst. The SON and PVN, which receive projections from the SFO, synthesize the peptide vasopressin, which is stored in the NH nerve terminals and is released into the circulation under conditions of hypovolaemia and hyperosmolality.

2. Although neuropharmacological methods are still of fundamental importance for the understanding of the central nervous system (CNS), the techniques of gene transfer to the CNS that have been developed recently provide a new means to study and influence neural function. A key vector for delivering reporter or functional genes to the brain has been replication‐deficient adenovirus, because it is safer, can be generated in high titres, can transfect non‐dividing cells and can be retrogradely transported from nerve terminals to somata.

3. In the present review, we describe new approaches that have been developed to transfer genes to the SFO, SON, PVN and NH cells bothin vitroandin vivo. We have defined the adenoviral concentrations required to optimize gene expression without causing cytotoxicity and an inflammatory response in the target cells. Gene transfer is an important tool to reveal mechanisms of SFO and SON control of cardiovascular homeostasis and may provide a therapeutic approach for prevention and/or treatment of pathophysiologies, such as arterial hypertension and genetic diabetes insipidus.
Proceedings of the Australian Physiological and Pharmacological Society Symposium: New Frontiers in Muscle Research The power of single channel recording and analysis: its application to ryanodine receptors in lipid bilayers
Authors: Laver DR
Published: March 2003

1. Since the inception of the patch‐clamp technique, single‐channel recording has made an enormous impact on our understanding of ion channel function and its role in membrane transport and cell physiology.

2. However, the impact of single‐channel recording methods on our understanding of intracellular Ca2+ regulation by internal stores is not as broadly recognized. There are several possible reasons for this.

3. First, ion channels in the membranes of intracellular organelles are not directly accessible to patch pipettes, requiring other methods that are not as widely known as the patch‐clamp techniques.

4. Second, bulk assays for channel activity have proved successful in advancing our knowledge of Ca2+ handling by intracellular stores. These assays include Ca2+ imaging, ryanodine binding assays and measurements of muscle tension and Ca2+ release and uptake by vesicles that have been isolated from internal stores.

5. The present review describes methods used for single‐ channel recording and analysis, as applied to the calcium release channels in striated muscle, and details some of the unique contributions that single‐channel recording and analysis have made to our current understanding of the release of Ca2+ from the internal stores of muscle.

6. With this in mind, the review focuses on three aspects of channel function and shows how single‐channel investigations have led to an improved understanding of physiological processes in muscle.

7. Finally, the review describes some of the latest improvements in membrane technology that will underpin future advances in single‐channel recording.
Proceedings of the Australian Physiological and Pharmacological Society Symposium: New Frontiers in Muscle Research Does Ca2+ release from the sarcoplasmic reticulum influence heart rate?
Authors: Ju Yue‐Kun , Allen David G
Published: March 2003

1. The present review summarizes the evidence that Ca2+ release from the sarcoplasmic reticulum (SR) is an important contributor to the systolic rise in [Ca2+]i (the Ca2+ transient) and influences the pacemaker firing rate.

2. We believe that the mechanism whereby [Ca2+]i influences firing rate is through the dependence of the Na+–Ca2+ exchanger on [Ca2+]i.

3. Extrusion of Ca2+ by the electrogenic Na+–Ca2+ exchanger produces an inward current that contributes to the pacemaker currents. Confocal images of Ca2+ indicate the distribution of [Ca2+]i and Ca2+ sparks add to the evidence that Ca2+ release from SR is involved in pacemaker activity.

4. The normal pathway for increased heart rate is sympathetic activation; we discuss the evidence that part of the chronotropic effect of β‐adrenoceptor stimulation is through the modulation of SR Ca2+ release.

5. These studies show that Ca2+ handling by the pacemaker cells makes an important contribution to the regulation of pacemaker activity.
Effects Of Milrinone On Left Ventricular End‐Systolic Pressure–Volume Relationship Of Rat Hearts In Situ
Authors: Kishi Takashi , Nakahashi Kazuyoshi , Ito Haruo , Taniguchi Shigeki , Takaki Miyako
Published: March 2003

1. We have already shown that the left ventricular (LV) end‐systolic pressure–volume relationship (ESPVR) of rat hearts in situ is an upward convex curve and that LV end‐ systolic pressure (ESPmLVV) and the systolic pressure–volume area (PVAmLVV) at a mid‐range LV volume (mLVV) sensitively reflect acute changes in LV contractility and work capability. Milrinone is a non‐glycosidic, non‐sympathomimetic drug that increases myocardial cAMP concentrations by selective inhibition of cardiac phosphodiesterase III. Therefore, milrinone could act on the entire cardiovascular system and cause an increase in inotropy, arterial vasodilatation and venodilatation. The aim of the present study was to investigate whether the approach we have recently instituted is able to detect the effects of milrinone on the entire cardiovascular system.

2. We measured simultaneously, in anaesthetized rats, continuous LV pressure using a catheter‐tip micromanometer and LV volume by LV volumetry using a conductance catheter. We obtained steady state LV pressure–volume loops and intermittently obtained the LV ESPVR by gradual occlusion of the ascending aorta. We then evaluated LV function by assessing milrinone‐induced changes in the ESPVR (i.e. ESPmLVV and PVAmLVV) and vasodilator actions by assessing milrinone‐induced changes in ESPESV and effective arterial elastance (Ea), defined as the ESPESV/stroke volume ratio.

3. Milrinone (total dose 49.5 μg; infusion rate 3.3–6.7 μg/min, 7–10 μg/kg per min; blood concentration 53.9 ng/mL) largely shifted the ESPVR upwards and, thus, significantly increased end‐systolic pressure (ESP0.08) and the systolic pressure–volume area (PVA0.08) at a mid‐range LV volume (= 0.08 mL/g myocardium). Milrinone also significantly decreased LV ESPESV and decreased Ea, although these decreases were not significant.

4. The results of the present study suggest that our own recently instituted approach to evaluate LV function by measuring LV pressure–volume loops and ESPVR succeeded in detecting a cardiotonic action of milrinone with arterial vasodilatation in normal rat hearts.
Effects Of Nitric Oxide Synthase Inhibition And Low‐Salt Diet On Blood Pressure And Mesenteric Resistance Artery Remodelling In Genetically Hypertensive Rats
Authors: Ledingham Janet M , Laverty Richard
Published: March 2003

1. Nitric oxide synthase (NOS)‐inhibited genetically hypertensive (GH) rats on normal and low‐sodium diets were additionally given valsartan or felodipine to establish whether low‐Na intake would have extra beneficial effects on blood pressure and cardiovascular structure.

2. Male GH rats on normal or low‐Na diets were treated with the NOS inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME) from the age of 7 to 12 weeks and were given either valsartan (10 mg/kg per day) or felodipine (30 mg/kg per day).

3. Systolic blood pressure (SBP; tail‐cuff) was measured weekly. At 12 weeks of age, mesenteric resistance arteries (MRA) were fixed by perfusion and embedded in Technovit (Heraeus Kulzer GmbH, Werheim, Germany). Serial sections were cut and stained. Stereological analysis was used to obtain MRA media width, lumen diameter, ratio of media width/lumen diameter (M/L) and medial cross‐sectional area (CSA). Left ventricular (LV) mass was determined.

4. In GH L‐NAME‐treated rats on a normal diet, SBP was significantly reduced (P < 0.001) by valsartan and felodipine, as was LV mass (valsartan P < 0.001; felodipine P < 0.05). A low‐Na diet with valsartan caused a further fall in SBP (P < 0.01) but, with felodipine, SBP increased in rats on a low‐Na diet (P < 0.05).

5. Valsartan with the low‐Na diet had no further effect on LV mass, but the felodipine‐treated group on a low‐Na diet had a lower LV mass (P < 0.05) than rats on a normal diet.

6. In MRA from the GH L‐NAME + valsartan‐treated group, there was hypotrophic inward remodelling; the M/L ratio was reduced (P < 0.001) compared with GH L‐NAME‐treated rats. The lumen was outwardly remodelled in the group on the low‐Na diet.

7. The GH L‐NAME + felodipine‐treated group showed hypotrophic outward remodelling and a reduction in M/L ratio compared with the GH L‐NAME‐treated group (P < 0.001). A low‐Na diet had no further effect on MRA.

8. A low‐Na diet + valsartan had beneficial effects on SBP and MRA, where outward remodelling of the lumen occurred and, thus, resistance was reduced. In contrast, felodipine with a low‐Na diet increased SBP, reduced LV mass and had no effect on MRA structure. Valsartan treatment with a low‐Na diet confers extra benefits on blood pressure and MRA structure.
Effects Of Hydrogen Peroxide On The Transient Outward Current In Rabbit Atrial Myocytes
Authors: Tanaka Hideo , Habuchi Yoshizumi , Suto Fumiaki , Morikawa Junichiro
Published: March 2003

1. In the present study, we investigated the effects of hydrogen peroxide (H2O2) on the 4‐aminopyridine‐sensitive transient outward current (ITO) in rabbit atrial myocytes using the amphotericin B‐perforated patch voltage‐clamp method.

2. Superfusion of myocytes with H2O2 at 100 μmol/L gradually slowed the time‐course of inactivation of ITO and increased the peak by 9% (n = 9). The H2O2‐induced slowing of ITO inactivation was concentration dependent (over the concentration range 10 μmol/L to 1 mmol/L). These effects were hardly reversed by washout of H2O2, but were quickly abolished by dithiothreitol (2 mmol/L).

3. Bisindolylmaleimide (100 nmol/L), an inhibitor of protein kinase C, significantly attenuated the H2O2‐induced effects on ITO.

4. These results suggest that rabbit atrial ITO is susceptible to oxidation by H2O2 at concentrations relevant to those encountered during ischaemia/reperfusion and that protein kinase C modulates the effects of H2O2.
Nitric Oxide Synthase Activity In Adrenocorticotrophin‐Induced Hypertension In The Rat
Authors: Turner Sw , Mangos Gj , Whitworth Ja
Published: March 2003

1. The nitric oxide (NO) system has been implicated in the pathogenesis of various forms of experimental hypertension. We studied nitric oxide synthase (NOS) activity as a possible indicator of NO production in adrenocorticotrophin (ACTH)‐induced hypertension in the rat.

2. Haemodynamic, metabolic and biochemical parameters were examined in sham (saline)‐ and ACTH (100 μg/kg per day)‐treated male Sprague‐Dawley rats (n = 20).

3. Adrenocorticotrophin treatment increased systolic blood pressure, serum corticosterone, adrenal NOS activity and adrenal nitrate and nitrite concentrations and decreased bodyweight and plasma nitrate/nitrite.

4. Previous observations of diminished NO production in ACTH‐ and corticosterone‐induced hypertension in the rat were confirmed, but could not be explained by reduced NOS activity in the present study.
Effect Of α‐Adrenoceptor Blockade On The 0.4 Hz Sympathetic Rhythm In Conscious Rats
Authors: Barrès Christian , Neto Edmundo Pereira de Souza , Julien Claude
Published: March 2003

1. The present study examined the origin of the 0.4 Hz rhythm in renal sympathetic nerve activity (RSNA) in rats. It was anticipated that, after elimination of 0.4 Hz oscillations of arterial pressure (AP) by α‐adrenoceptor blockade, the persistence or disappearance of a 0.4 Hz rhythm in RSNA would point to an endogenous (central oscillator) or baroreflex origin, respectively.

2. Arterial pressure and RSNA were recorded in seven conscious rats, before and after acute α‐adrenoceptor blockade with phentolamine (5 mg/kg, i.v.). In each condition, power and coherence spectra were calculated over 15 min periods of rest.

3. In control conditions, highly coherent AP and RSNA oscillations were observed near 0.4 Hz. After phentolamine administration, spectral power in the mid‐frequency (0.27–0.74 Hz) band was significantly reduced for both AP and RSNA and maximum power was shifted towards 0.7 Hz.

4. The disappearance of the RSNA rhythm at 0.4 Hz after phentolamine administration favours the hypothesis of a baroreflex origin. The new oscillation near 0.7 Hz can derive either from the activity of a previously unrecognized central oscillator or from a faster feedback mechanism involving cotransmitters of noradrenaline acting with shorter time constants (e.g. ATP).
Endothelin Blockade In Angiotensin Ii Hypertension: Prevention And Treatment Studies In The Rat
Authors: Ficai Sylvia , Herizi Abderraouf , Mimran Albert , Jover Bernard
Published: March 2003

1. The participation of endothelin (ET) in the development and maintenance of hypertension induced by angiotensin (Ang) II was assessed using the non‐specific ET receptor antagonist bosentan (30 mg/kg per day).

2. In the prevention study, bosentan was given 24 h prior to and during the 17 day period of AngII infusion (200 ng/kg per min, s.c., osmotic pump), whereas in the treatment study, bosentan was administered from day 10 to day 17. Tail‐cuff pressure (TCP) was measured before and on days 10 and 17 of AngII infusion. At the end of studies, heart weight index was calculated as the ratio of heart to bodyweight (HWI) and the wall thickness of the carotid artery (perfusion/fixation at 120 mmHg) was measured. Tail‐cuff pressure increased from 129 ± 3 to 179 ± 7 and 189 ± 9 mmHg on days 10 and 17 of AngII infusion, respectively.

3. Final TCP was markedly lowered in rats pretreated with bosentan, whereas TCP remained comparable with untreated hypertensive rats when bosentan was given from day 10 of AngII infusion (177 ± 9 mmHg).

4. The increase in cardiac mass associated with AngII hypertension was similarly attenuated in the two groups receiving bosentan.

5. The HWI was 3.49 ± 0.12 mg/g in untreated hypertensive rats and 3.18 ± 0.08 and 3.11 ± 0.09 mg/g in rats pretreated with bosentan and those receiving the antagonist from day 10.

6. The increase in carotid wall thickness induced by AngII was prevented, but not reversed, by bosentan.

7. These results support the hypothesis that endogenous ET participates only in the initial phase of AngII hypertension. In addition, the beneficial effect of bosentan of cardiac mass but not on arterial wall thickness is in favour of a role of ET as a local mediator of the cardiac hypertrophic effect of AngII, independently of the level of blood pressure and duration of hypertension.