bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect Of Experimental Diabetes On Gaba‐Mediated Inhibition Of Neurally Induced Contractions In Rat Isolated Trachea
Authors: Özdem Sadi S , Sadan Gülay , Usta Coskun , Tasatargil Arda
Published: March 2003

1. In the present study, we investigated the effect of GABA and selective GABA agonists and antagonists on neurally induced tracheal contractions in streptozotocin (STZ) diabetic rats.

2. Contractile responses to electrical field stimulation (EFS) in rat tracheal rings were completely abolished by atropine and tetrodotoxin, but were unaffected by the ganglion blocker hexamethonium, indicating that they were mediated via neuronal release of acetylcholine (ACh).

3. Contractions induced by EFS, but not by exogenous ACh, were inhibited by GABA and the selective GABAB receptor agonist baclofen, but not by the selective GABAA receptor agonist 3‐aminopropane sulphonic acid. The inhibitory effects of GABA or baclofen were not affected by the GABAA antagonist bicuculline, but were significantly reversed by the GABAB antagonist phaclofen.

4. The inhibitory effects of both GABA and baclofen were found to be significantly greater in trachea from control rats compared with tissues from diabetic rats.

5. Non‐adrenergic, non‐cholinergic relaxation responses elicited by EFS in precontracted tracheal rings from diabetic and control rats were similar in magnitude and were unaffected by GABA or GABA analogues.

6. These results suggest that GABA decreases the response to EFS by directly inhibiting the evoked release of ACh through GABAB receptors in rat trachea and that STZ‐induced diabetes causes an impairment in the inhibitory effect of GABA on neurally induced contractions in this tissue.
Relative Timing Of Inspiration And Expiration Affects Respiratory Sinus Arrhythmia
Authors: Strauss‐Blasche G , Moser M , Voica M , McLeod Dr , Klammer N , Marktl W
Published: March 2003

1. The effect of a variation in inspiration and expiration times on heart rate variability was studied in 12 healthy subjects (mean age 30±6 years; five females).

2. Two 2 min trials of controlled breathing, with either short inspiration followed by long expiration or long inspiration followed by short expiration, were compared. Average expiration/inspiration time ratios were 1.0 and 3.4, respectively. The respiration rate in both trials was approximately 10 cycles/min.

3. In trials with short inspiration followed by long expiration, respiratory sinus arrhythmia (RSA; as measured by mean absolute differences and by the high frequency band) was significantly larger than in trials with long inspiration followed by short expiration. This effect could not be accounted for by differences in respiration rate or respiratory amplitude. The higher RSA during fast/slow respiration is primarily due to a more pronounced phasic heart rate increase during inspiration, indicating that inspiratory vagal blockade is sensitive to the steepness of inspiration.

4. Respiration rate and tidal volume are respiratory variables known to modulate RSA. The results of the present study indicate that RSA can also be modulated by a third respiratory variable, the expiratory/inspiratory time ratio.
Role Of Voltage‐Gated Na+ Channels In Hypoxia‐Induced Neuronal Injuries
Authors: Fung Man‐Lung
Published: March 2003

1. Mammalian neurons in the central nervous system are vulnerable to oxygen deprivation. In clinical conditions, such as stroke or apnoea, permanent loss of neuronal functions can occur within minutes of severe hypoxia.

2. Recent studies have focused on the role of Na+ in acute neuronal responses to hypoxia. These studies have shown that the influx of extracellular Na+ is an important factor in hypoxia‐induced injury and that blockade of voltage‐gated Na+ channels reduces hypoxic responses and injury of neurons. Yet, the mechanism underlying the effect of blockade of Na+ channels on hypoxic injury is unclear.

3. The aim of the present review is to discuss the above topics given the current understanding of the role of Na+ channels in hypoxia and its implications on therapeutic strategy for preventing hypoxia‐induced neurological damage.

4. It has been known that the maintenance of ionic homeostasis and membrane properties in neurons are improved by reducing the activity of voltaged‐gated Na+ channels during acute hypoxia.

5. Recent studies suggest that persistent Na+ current and Na+‐dependent exchangers may play a role in Na+ influx and neuronal injury during hypoxia.

6. The neuroprotective action of blockers of the Na+ channel may also be via the improved maintainence of intracellular energy levels because the action is dependent on cellular energy levels and extracellular glucose during hypoxia.

7. Hence, the blockade of voltage‐gated Na+ channels reduces the excitability of neurons, Na+ influx and the accumulation of intracellular Na+. These improve the ionic homeostasis and cellular energy levels and, thus, prevent hypoxia‐induced neuronal injury and neuronal damage mediated by Ca2+ overload.
Impaired Heart Function And Noradrenaline Release After Ischaemia In Stroke‐Prone Spontaneously Hypertensive Rats
Authors: Chen Hong , Azuma Makiko , Maeda Kana , Kajimoto Noriyoshi , Higashino Hideaki
Published: March 2003

1. Stroke‐prone spontaneously hypertensive rats (SHRSP) are a strain of rat that exhibit severely high blood pressure and stroke attacks at an early age, but their heart function in vitro has seldom been studied in detail. Although the activity of the sympathetic nervous system is known to increase after myocardial ischaemia, there is little information about the cardiac release of noradrenaline (NA) associated with heart function after ischaemia in SHRSP. The aim of the present study was to examine heart function and cardiac NA release after ischaemia in SHRSP.

2. Isolated hearts of 4‐ and 8‐month‐old SHRSP and age‐matched Wistar‐Kyoto (WKY) rats were perfused in a working heart preparation and were subjected to 30 min ischaemia followed by 30 min reperfusion. Heart function and coronary flow were monitored throughout the experiment. Coronary effluent was collected for determination of NA using high‐ performance liquid chromatography coupled with electrochemical detection.

3. Under baseline conditions, cardiac output of 4‐month‐old SHRSP was slightly but significantly decreased compared with that of WKY rats (P < 0.05), although coronary flow was maintained normally at this age. Eight‐month‐old SHRSP showed a further impairment of systolic heart function, with lower coronary flow and higher coronary vascular resistance under baseline conditions. Elevated left ventricular end‐diastolic pressure was evident in SHRSP at both ages before ischaemia. Heart function was severely damaged after 30 min global ischaemia in SHRSP from both age groups. Stroke‐prone spontaneously hypertensive rats also showed lower coronary flow and higher coronary vascular resistance during reperfusion.

4. Coronary NA was not detectable in WKY rats or SHRSP at 4 months of age under baseline conditions. In 8‐month‐old SHRSP, pre‐ischaemic NA release was significantly higher than that in age‐matched WKY rat controls. The concentration of NA in the coronary effluent of SHRSP during reperfusion was also significantly higher than that of WKY rats at both ages.

5. These data demonstrate that SHRSP have early impairment of both systolic and diastolic heart function compared with WKY rats. Severe damage of heart function and coronary flow after ischaemia in SHRSP was accompanied with an increased release of NA, which may play a harmful role in heart function impairment in SHRSP after ischaemia.
Introduction: A Brief History Of Capillaries And Some Examples Of Their Apparently Strange Behaviour
Authors: Baldwin Ann L
Published: March 2003

1. Over the past decade, evidence has accumulated challenging the notion that the smallest blood vessels, the capillaries, are static, uniform, semipermeable pipes with no function except as a passive barrier marking the boundary between the vascular compartments from the tissue compartment.

2. Instead, capillaries are dynamic structures that participate in the active regulation of water, waste and nutrient exchange, the formation and destruction of exchange vessels and the sites for initiation of signals to regulate the flow of blood into the exchange vascular network.

3. The following papers will provide insight into the expanded appreciation of the varied nature of capillaries and how their functions are co‐ordinated to achieve ‘whole organ’ exchange.
Diversity Within Pericytes
Authors: Sims David E
Published: March 2003

1. Pericytes are cells of microvessels (arterioles, capillaries and venules) that wrap around endothelial cells. They are most abundant on venules and are common on capillaries.

2. The pericyte population is highly variable between different tissues and organs, probably in a manner reflecting postarteriolar hydrostatic pressures. Pericytes are more abundant in the distal legs and feet, again suggesting a hydrostatic pressure‐driven mechanical role for pericytes as protectors of microvessel wall integrity.

3. Pericyte alteration or degeneration is linked directly with microangiopathy in diabetes, scleroderma, hypertension, dementias and, possibly, inappropriate calcification of blood vessels.

4. Pericytes are functionally codependent on endothelial cells. Each cell type influences each others’ mitotic rate and probably phenotypic expression.

5. Pericytes are not randomly located around microvessels. Instead, they are located adjacent to or over endothelial cell junctions of venules and especially over gaps between endothelial cells during inflammation. Pericytes are emerging as essential components of the microvessel wall, with metabolic, signalling and mechanical roles to support the endothelial cell.
Circular Muscle Contraction, Messenger Signalling And Localization Of Binding Sites For Neurokinin A In Human Sigmoid Colon
Authors: Warner Fiona J , Liu Lu , Lubowski David Z , Burcher Elizabeth
Published: March 2003

1. Neurokinin (NK)A is the endogenous ligand for the tachykinin NK2 receptor. In the present study, tachykinins and selective receptor agonists were tested as contractile agonists in human colon circular muscle and [125I]‐NKA was used to localize binding sites in human colon.

2. In strips of circular muscle, removal of mucosa and submucosa significantly (P < 0.05) increased the potency and the maximum response achieved by NKA.

3. The rank order of potency of tachykinin and selective receptor agonists in contracting circular muscle strips was NKA ≥ [Lys 5,MeLeu
9,Nle
10]NKA(4–10) ≥ neuropeptide (NP)γ≥ [βAla
8]NKA(4–10) » NKB > substance P (SP) » senktide ≈ [Pro
9]SP.

4. Specific binding sites for [125I]‐NKA were densely localized over circular muscle and muscularis mucosae. Weak specific binding was seen on longitudinal muscle and taenia coli, whereas no binding sites were seen on mucosa, ganglia or blood vessels.

5. In circular muscle, the selective NK2 receptor agonist [Lys
5,MeLeu
9,Nle
10]NKA(4–10) produced weak increases (maximum 37%) in inositol monophosphate formation with a pD2 of 6.8±0.51 (n = 3). Carbachol (100 μmol/L) was also a weak stimulant (maximum 45%). These agonists were over 10‐fold more efficacious in stimulation of inositol monophosphate in rat urinary bladder.

6. In conclusion, [125I]‐NKA binding sites localized on human colon circular muscle were characterized as NK2 receptors. Functionally, the tachykinin NK2 receptor is mediating circular smooth muscle contraction. Although the human NK2 receptor is coupled to the phosphatidylinositol pathway, other second messenger mechanisms may also operate in this tissue.
Proceedings of the Australian Neuroscience Society Symposium: Schizophrenia MOLECULAR GENETICS OF SCHIZOPHRENIA
Authors: Mowry Bj , Nancarrow Dj
Published: March 2003

1. Schizophrenia is a chronic, disabling brain disease that affects approximately 1% of the world’s population. It is characterized by delusions, hallucinations and formal thought disorder, together with a decline in socio‐occupational functioning. While the causes for schizophrenia remain unknown, evidence from family, twin and adoption studies clearly demonstrates that it aggregates in families, with this clustering largely attributable to genetic rather than cultural or environmental factors. Identifying the genes involved, however, has proven to be a difficult task because schizophrenia is a complex trait characterized by an imprecise phenotype, the existence of phenocopies and the presence of low disease penetrance.

2. The current working hypothesis for schizophrenia causation is that multiple genes of small to moderate effect confer compounding risk through interactions with each other and with non‐genetic risk factors. The same genes may be commonly involved in conferring risk across populations or they may vary in number and strength between different populations. To search for evidence of such genetic loci, both candidate gene and genome‐wide linkage studies have been used in clinical cohorts collected from a variety of populations. Collectively, these works provide some evidence for the involvement of a number of specific genes (e.g. the 5‐hydroxytryptamine (5‐HT) type 2a receptor (5‐HT2a) gene and the dopamine D3 receptor gene) and as yet unidentified factors localized to specific chromosomal regions, including 6p, 6q, 8p, 13q and 22q. These data provide suggestive, but no conclusive, evidence for causative genes.

3. To enable further progress there is a need to: (i) collect fine‐grained clinical datasets while searching the schizophrenia phenotype for subgroups or dimensions that may provide a more direct route to causative genes; and (ii) integrate recent refinements in molecular genetic technology, including modern composite marker maps, DNA expression assays and relevant animal models, while using the latest analytical techniques to extract maximum information in order to help distinguish a true result from a false‐positive finding.
Annual Scientific Meeting of ASCEPT, 1999 Immune‐Derived Opioids And Peripheral Antinociception
Authors: Cabot Pj
Published: March 2003

1. Recent findings have suggested a significant involvement of the immune system in the control of pain. Immune cells contain opioid peptides that are released within inflamed tissue and act at opioid receptors on peripheral sensory nerve endings. It is also apparent that different types of lymphocytes contain β‐endorphin, memory T cells containing more β‐endorphin than naïve cells.

2. These findings highlight an integral link between immune cell migration and inflammatory pain. The present review highlights immune system involvement in the site‐directed control of inflammatory pain.

3. Full‐length mRNA transcripts for opioid precursor proteins are expressed in immune cells. Increased expression of pro‐opiomelanocortin mRNA and β‐endorphin has been demonstrated in stimulated lymphocytes and lymphocytes from animals with inflammation.

4. Cytokines and corticotropin‐releasing factor (CRF) release opioids from immune cells. Potent peripheral analgesia due to direct injection of CRF can be blocked by antagonists to CRF, antibodies to opioid peptides, antisense to CRF and opioid receptor‐specific antagonists. The release of opioid peptides from lymphocytes is calcium dependent and opioid receptor specific. Furthermore, endogenous sources of opioid peptides produce potent analgesia when implanted into the spinal cord.

5. Activated immune cells migrate directly to inflamed tissue using cell adhesion molecules to adhere to the epithelial surface of the vasculature in inflamed tissue. Lymphocytes that have been activated can express opioid peptides. Memory type T cells that contain opioid peptides are present within inflamed tissue; naïve cells are not present in inflamed tissue and do not contain opioid peptides. Inhibiting the migration of memory type T cells into inflamed tissue by blocking selectins results in reduced numbers of β‐endorphin‐containing cells, a reduced quantity of β‐endorphin in inflamed paws and reduced stress‐ and CRF‐induced peripheral analgesia.

6. Immunosuppression is associated with increased pain in patients. Moreover, immunosuppression results in decreased lymphocyte numbers as well as decreased analgesia in animal models.
Annual Scientific Meeting of ASCEPT, 1999 Role Of Human Airway Smooth Muscle In Altered Extracellular Matrix Production In Asthma
Authors: Johnson Peter Robert Arundel
Published: March 2003

1. The underlying abnormality in asthma is not fully understood; however, inflammation, airway remodelling and bronchial hyperresponsiveness are key factors. The plasma exudate from the microvascular leakage plays a significant role in remodelling, which includes extracellular matrix (ECM) protein deposition/ breakdown and airway smooth muscle (ASM) hyperplasia/ hypertrophy.

2. The ECM is an intricate network of macromolecules that forms the ‘scaffolding’ of the airways. This scaffolding not only acts as mechanical support that plays a crucial role in the maintenance of airway function and structure, but it is also a dynamic and complex network that has the potential to influence cellular function, including migration, differentiation and proliferation of a number of cell types.

3. In asthmatic airways, the profile of ECM proteins is altered. The deposition of collagen I, III, V, fibronectin, tenascin, hyaluronan, versican and lamininα2/β2 is increased, whereas the deposition of collagen IV and elastin is decreased.

4. This imbalance in the ECM profile within the asthmatic airway could be due to: (i) increasedde novosynthesis of ECM proteins; (ii) decreased activity of its degrading enzymes, namely matrix metalloproteinases (MMP); or (iii) upregulation of the tissue‐specific inhibitors of metalloproteinases (TIMP).

5. One of the characteristic features of asthma is an increase in the amount of ASM within the airways. The ECM proteins/MMP/TIMP in and around the smooth muscle may play a contributory role in this increased growth.

6. The role of current asthma treatments in the prevention or reversal of airway ECM changes is an area that has only recently become of interest, with the majority of thein vivowork focusing on the effects of corticosteroids.

7. The evidence presented in this review indicates that the ASM may influence its own environment/proliferation through the production of ECM proteins, MMP and TIMP. Further studies are needed to fully understand the role of the ASM in the production of ECM proteins, MMP and TIMP and their potential influence in the mechanisms underlying asthma.
Chronic Administration Of Docosahexaenoic Acid Improves The Performance Of Radial Arm Maze Task In Aged Rats
Authors: Gamoh Shuji , Hashimoto Michio , Hossain Shahdat , Masumura Sumio
Published: March 2003

1. In the present study, we investigated the effect of docosahexaenoic acid (DHA) on spatial memory related learning ability in aged (100 weeks) male Wistar rats.

2. Rats were fed a fish oil‐deficient diet through three generations and were then randomly divided into two groups. Over 10 weeks, one group was per orally administered 300 mg/kg per day DHA dissolved in 5% gum Arabic solution and the other group was administered the vehicle alone. Five weeks after the start of the administration, rats were tested with the partially baited eight‐arm radial maze to estimate two types of spatial memory related learning ability displayed by reference memory error and working memory error.

3. Chronic administration of DHA significantly decreased the number of reference memory errors and working memory errors.

4. The level of lipid peroxide (LPO) in the hippocampus tended to decrease with chronic DHA administration and demonstrated a positive correlation with the number of reference memory errors.

5. These results suggest that the accumulation of hippocampal LPO reduces spatial memory related learning ability in aged rats. Moreover, chronic administration of DHA was effective in decreasing the level of hippocampal LPO, then improving learning ability.
New Perspectives On The Role Of Aldosterone Excess In Cardiovascular Disease
Authors: Stowasser Michael
Published: March 2003

1. Evidence from recent experimental and clinical studies suggests that excessive circulating levels of aldosterone can bring about adverse cardiovascular sequelae independent of the effects on blood pressure. Examples of these sequelae are the development of myocardial and vascular fibrosis in uninephrectomized, salt‐loaded rats infused with mineralocorticoids and, in humans, an association of aldosterone with left ventricular hypertrophy, impaired diastolic and systolic function, salt and water retention causing aggravation of congestion in patients with established congestive cardiac failure (CCF), reduced vascular compliance and an increased risk of arrhythmias (resulting from intracardiac fibrosis, hypokalaemia, hypomagnesaemia, reduced baroreceptor sensitivity and potentiation of catecholamine effects).

2. These sequelae of aldosterone excess may contribute to the pathogenesis and worsen the prognosis of CCF and hypertension.

3. The heart and blood vessels may be capable of extra‐adrenal aldosterone biosynthesis, raising the possibility that aldosterone may have paracrine or autocrine (and not just endocrine) effects on cardiovascular tissues.

4. The high prevalence of CCF, which is associated with secondary aldosteronism, and primary aldosteronism (PAL; recently recognized to be a much more common cause of hypertension than was previously thought) argue for an important role for aldosterone excess as a cause of cardiovascular injury.

5. The recognition of non‐blood pressure‐dependent adverse sequelae of aldosterone excess raises the question as to whether normotensive individuals with PAL, who have been detected as a result of genetic or biochemical screening among families with inherited forms of PAL, are at excess risk of cardiovascular events.

6. Provided that patients are carefully investigated in order to permit the appropriate selection of specific surgical (laparoscopic adrenalectomy for PAL that lateralizes on adrenal venous sampling) or medical (treatment with aldosterone antagonist medications) management and safety considerations for the use of aldosterone antagonists are kept in mind, the appreciation of a widening role for aldosterone in cardiovascular disease should provide a substantially better outlook for many patients with CCF and hypertension.
Comparison Of Telemetric And Tail‐Cuff Blood Pressure Monitoring In Adrenocorticotrophic Hormone‐Treated Rats
Authors: Fraser Tafline B , Turner Steven W , Mangos George J , Ludbrook John , Whitworth Judith A
Published: March 2003

1. The aim of the present study was to validate a telemetric blood pressure (BP) monitoring system against tail‐cuff blood pressure in both adrenocorticotrophic hormone (ACTH)‐ and sham‐treated rats. In the statistical analyses, we first tested whether there was a detectable effect on systolic blood pressure (SBP) of 10 days treatment with ACTH compared with saline. Second, we compared results of telemetered and tail‐cuff measurements and, third, we developed a novel method for estimating the relative power of the two techniques.

2. Twenty‐three male Sprague‐Dawley rats were randomly divided into two groups: (i) ACTH (100 μg/kg per day, s.c.; n = 12) treated; or (ii) sham treated (0.9% saline, s.c.; n = 11). Systolic BP was measured by the telemetric system (sampled for 10 s every 2 min) continuously for 4 h (n = 16) or for 30 min (n = 23) and also by the indirect tail‐cuff method daily (n = 23). Data were compared within and between groups; ordinary least products (OLP) regression analysis was then performed to test for bias between the two methods. Sample size/power estimations were also performed.

3. Adrenocorticotrophic hormone treatment raised telemetered SBP by 11 mmHg (P < 0.001) compared with 14 mmHg (P < 0.001) using the tail‐cuff method. There was no fixed or proportional bias between the two methods of measurement, as shown by regression analysis. Power calculations indicate that a minimum sample size of six gives a power of telemetered to tail‐cuff of 0.84/0.86 = 0.98. The power of 4 h versus 30 min BP measurements was 0.99/0.82 = 1.2.

4. Telemetry gave very similar results to the tail‐cuff method. Telemetry allows for a longer period of measurement, giving greater power to the study so that fewer animals are needed.
Increased Cerebral Blood Flow And Cardiac Output Following Cerebral Arterial Air Embolism In Sheep
Authors: Williams David J , Doolette David J , Upton Richard N
Published: March 2003

1. The effects of cerebral arterial gas embolism on cerebral blood flow and systemic cardiovascular parameters were assessed in anaesthetized sheep.

2. Six sheep received a 2.5 mL injection of air simultaneously into each common carotid artery over 5 s. Mean arterial blood pressure, heart rate, end‐tidal carbon dioxide and an ultrasonic Doppler index of cerebral blood flow were monitored continuously. Cardiac output was determined by periodic thermodilution.

3. Intracarotid injection of air produced an immediate drop in mean cerebral blood flow. This drop was transient and mean cerebral blood flow subsequently increased to 151% before declining slowly to baseline. Coincident with the increased cerebral blood flow was a sustained increase in mean cardiac output to 161% of baseline. Mean arterial blood pressure, heart rate and end‐tidal carbon dioxide were not significantly altered by the intracarotid injection of air.

4. The increased cardiac output is a pathological response to impact of arterial air bubbles on the brain, possibly the brainstem. The increased cerebral blood flow is probably the result of the increased cardiac output and dilation of cerebral resistance vessels caused by the passage of air bubbles.
Pharmacotherapy Of The Ion Transport Defect In Cystic Fibrosis
Authors: Kunzelmann Karl , Mall Marcus
Published: March 2003

1. More than 1300 different mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) cause cystic fibrosis (CF), a disease characterized by deficient epithelial Cl– secretion and enhanced Na+ absorption. The clinical course of the disease is determined by the progressive lung disease. Thus, novel approaches in pharmacotherapy are based primarily on correction of the ion transport defect in the airways.

2. The current therapeutic strategies try to counteract the deficiency in Cl– secretion and the enhanced Na+ absorption. A number of compounds have been identified, such as genistein and xanthine derivatives, which directly activate mutant CFTR. Other compounds may activate alternative Ca2+‐activated Cl– channels or basolateral K+ channels, which supply the driving force for Cl– secretion. Apart from that, Na+ channel blockers, such as phenamil and benzamil, are being explored, which counteract the hyperabsorption of NaCl in CF airways.

3. Clinical trials are under way using purinergic compounds such as the P2Y2 receptor agonist INS365. Activation of P2Y2 receptors has been found to both activate Cl– secretion and inhibit Na+ absorption.

4. The ultimate goal is to recover Cl– channel activity of mutant CFTR by either enhancing synthesis and expression of the protein or by activating silent CFTR Cl– channels. Strategies combining these drugs with compounds facilitating Cl– secretion and inhibiting Na+ absorption in vivo may have the best chance to counteract the ion transport defect in cystic fibrosis.
Angiotensin I‐Converting Enzyme And Metabolism Of The Haematological Peptide N‐Acetyl‐Seryl‐Aspartyl‐Lysyl‐Proline
Authors: Azizi Michel , Junot Christophe , Ezan Eric , Ménard Joël
Published: March 2003

1. Angiotensin I‐converting enzyme (ACE) has two homologous active N‐ and C‐terminal domains and displays activity towards a broad range of substrates. The tetrapeptide N‐acetyl‐seryl‐aspartyl‐lysyl‐proline (AcSDKP) has been shown to be hydrolysed in vitro by ACE and to be a preferential substrate for its N‐terminal active site. This peptide reversibly prevents the recruitment of pluripotent haematopoietic stem cells and normal early progenitors into the S‐phase.

2. Angiotensin I‐converting enzyme inhibitors, given as a single dose to normal subjects or during long‐term treatment in hypertensive patients, result in plasma AcSDKP levels five‐ to six‐fold higher and urine concentrations 40‐fold higher than those of control subjects and/or patients. Thus, AcSDKP is a natural peptide hydrolysed by the N‐terminal domain of ACE in vivo. In addition, ACE may be implicated in the process of haematopoietic stem cell regulation by permanently degrading this natural circulating inhibitor of cell entry into the S‐phase.

3. Besides hydrolysis by ACE, the second very effective mechanism by which AcSDKP is cleared from plasma is glomerular filtration. Because of its high sensitivity and specificity, the measurement of AcSDKP in plasma and urine provides a valuable tool in screening specific inhibitors of the N‐terminal domain of ACE and in monitoring ACE inhibition during chronic treatment.

4. The long‐term consequences of AcSDKP accumulation are not known. During chronic ACE inhibition in rats, AcSDKP levels slightly increase in organs with high ACE content (kidneys, lungs). To significantly increase its concentration in target haematopoietic organs (the extracellular fraction of bone marrow), AcSDKP has to be infused on top of a captopril‐based treatment.

5. A selective inhibitor of the N‐domain of ACE in vitro and in vivo has been identified recently. The phosphinic peptide RXP 407 does not interfere with blood pressure regulation, but does increase, dose dependently, plasma concentrations of AcSDKP in mice, in contrast with lisinopril, which affects the metabolism of both AcSDKP and angiotensin I. N‐Terminal‐selective ACE inhibitors may be used to selectively control AcSDKP metabolism in target haematopoietic organs. This new therapeutic strategy may be of value for protecting haematopoietic cells from the toxicity of cancer chemotherapy.
Molecular Diversity Of Vascular Potassium Channel Isoforms
Authors: Korovkina Victoria P , England Sarah K
Published: March 2003

1. One essential role for potassium channels in vascular smooth muscle is to buffer cell excitation and counteract vasoconstrictive influences. Several molecular mechanisms regulate potassium channel function. The interaction of these mechanisms may be one method for fine‐tuning potassium channel activity in response to various physiological and pathological challenges.

2. The most prevalent K+ channels in vascular smooth muscle are large‐conductance
calcium‐ and voltage‐sensitive channels (maxi‐K channels) and voltage‐gated channels
(Kv channels). Both channel types are complex molecular structures consisting of
a pore‐forming α‐subunit and an ancillary β‐subunit. The
maxi‐K and Kv channel α‐subunits assemble as tetramers and have S4 transmembrane
domains that represent the putative voltage sensor. While most vascular smooth muscle
cells identified to date contain both maxi‐K and Kv channels, the expression of individual
α‐subunit isoforms and β‐subunit association occurs in a tissue‐specific manner, thereby providing functional specificity.

3. The maxi‐K channel α‐subunit derives its molecular diversity by
alternative splicing of a single‐gene transcript to yield multiple isoforms that
differ in their sensitivity to intracellular Ca2+ and voltage, cell surface
expression and post‐ translational modification. The ability of this channel to assemble
as a homo‐ or heterotetramer allows for fine‐tuning control to intracellular regulators.
Another level of diversity for this channel is in its association with accessory
β‐subunits. Multiple β‐subunits have been identified that
can arise either from separate genes or alternative splicing of a β‐subunit
gene. The maxi‐K channel β‐subunits modulate the channel’s Ca2+ and voltage sensitivity and kinetic and pharmacological properties.

4. The Kv channel α‐subunit derives its diverse nature by the expression
of several genes. Similar to the maxi‐K channel, this channel has been shown to assemble
as a homo‐ and heterotetramer, which can significantly change the Kv current phenotype
in a given cell type. Association with a number of the ancillary β‐subunits affects Kv channel function in several ways. Beta‐subunits can induce inactivating properties and act as chaperones, thereby regulating channel cell‐surface expression and current kinetics.
Transcriptional Activation Of Energy Metabolic Switches In The Developing And Hypertrophied Heart
Authors: Lehman John J , Kelly Daniel P
Published: March 2003

1. The present review focuses on the gene regulatory mechanisms involved in the control of cardiac mitochondrial energy production in the developing heart and following the onset of pathological cardiac hypertrophy. Particular emphasis has been given to the mitochondrial fatty acid oxidation (FAO) pathway and its control by members of the nuclear receptor transcription factor superfamily.

2. During perinatal cardiac development, the heart undergoes a switch in energy substrate preference from glucose in the fetal period to fatty acids following birth. This energy metabolic switch is paralleled by changes in the expression of the enzymes and protein involved in the respective pathways.

3. The postnatal activation of the mitochondrial energy production pathway involves the induced expression of nuclear genes encoding FAO enzymes, as well as other proteins important in mitochondrial energy transduction/production pathways. Recent evidence indicates that this postnatal gene regulatory effect involves the actions of the nuclear receptor peroxisome proliferator‐activated receptor α (PPARα)
and its coactivator the PPARγ coactivator 1 (PGC‐1).

4. The PGC‐1 not only activates PPARα to induce FAO pathway enzymes in the postnatal heart, but it also plays a pivotal role in the control of cardiac mitochondrial number and function. Thus, PGC‐1 plays a master regulatory role in the high‐capacity mitochondrial energy production system in the adult mammalian heart.

5. During the development of pathological forms of cardiac hypertrophy, such as that due to pressure overload, the myocardial energy substrate preference shifts back towards the fetal pattern, with a corresponding reduction in the expression of FAO enzyme genes. This metabolic shift is due to the deactivation of the PPARα/PGC‐1 complex.

6. The deactivation of PPARα and PGC‐1 during the development of cardiac hypertrophy involves regulation at several levels, including a reduction in the expression of these genes, as well as post‐translational effects due to the mitogen‐activated protein kinase pathway. Future studies aim at defining whether this transcriptional ‘switch’ and its effects on myocardial metabolism are adaptive or maladaptive in the hypertrophied heart.
Altered Mitogen‐Activated Protein Kinase Activation In Vascular Smooth Muscle Cells From Spontaneously Hypertensive Rats
Authors: Kubo Takao , Ibusuki Takahiro , Chiba Satoshi , Kambe Toshie , Fukumori Ryuji
Published: March 2003

1. We previously reported that activation function of mitogen‐activated protein kinases (MAPK) is enhanced in aorta strips from both prehypertensive and hypertensive spontaneously hypertensive rats (SHR) and that this enhancement of MAPK activation results from enhanced MAPK activation reactivity to angiotensin (Ang) II in SHR aorta strips.

2. The purpose of the present study was to examine whether the enhanced function of the vascular angiotensin system observed in SHR aorta strips results from genetic alterations of vascular smooth muscle cells from SHR.

3. Basal MAPK activity was within normal limits in cells from 4‐week‐old SHR, whereas enzyme activity was enhanced in 9‐week‐old SHR compared with age‐matched Wistar‐Kyoto (WKY) rats.

4. Mitogen‐activated protein kinase activation reactivity to AngII and endothelin‐1 was enhanced in 9‐week‐old SHR cells but not in 4‐week‐old SHR cells. The enhancement of basal MAPK activity in 9‐week‐old SHR cells was abolished by a combination of the angiotensin AT1 receptor antagonist losartan and the endothelin receptor antagonist BQ123.

5. These findings suggest that MAPK activation function in 4‐week‐old SHR cells is not enhanced. Thus, it appears that factors outside vascular smooth muscle cells are needed for the enhanced MAPK activation observed in 4‐week‐old SHR aorta strips. In 9‐week‐old SHR, MAPK activation function is enhanced in cells themselves and this function may, at least in part, contribute to the enhanced MAPK activation observed in SHR aorta strips.
In vitro neuromuscular activity of snake venoms
Authors: Hodgson Wayne C , Wickramaratna Janith C
Published: March 2003

1. Snake venoms consist of a multitude of pharmacologically active components used for the capture of prey. Neurotoxins are particularly important in this regard, producing paralysis of skeletal muscles. These neurotoxins can be classified according to their site of action (i.e. pre‐ or post‐synaptic).

2. Presynaptic neurotoxins, which display varying phospholipase A2 activities, have been identified in the venoms of the four major families of venomous snakes (i.e. Crotalidae, Elapidae, Hydrophiidae and Viperidae). The blockade of transmission produced by these toxins is usually characterized by a triphasic effect on acetylcholine release. Considerable work has been directed at identifying the binding site(s) on the presynaptic nerve terminal for these toxins, although their mechanism of action remains unclear.

3. Post‐synaptic neurotoxins are antagonists of the nicotinic receptor on the skeletal muscle. Depending on their sequence, post‐synaptic toxins are subdivided into short‐ and long‐chain toxins. These toxins display different binding kinetics and different affinity for subtypes of nicotinic receptors. Post‐synaptic neurotoxins have only been identified in venoms from the families Elapidae and Hydrophiidae.

4. Due to the high cost of developing new antivenoms and the reluctance of many companies to engage in this area of research, new methodologies are required to test the efficacy of existing antivenoms to ensure their optimal use. While chicken eggs have proven useful for the examination of haemorrhagic venoms, this procedure is not suited to venoms that primarily display neurotoxic activity. The chick biventer cervicis muscle has proven useful for this procedure, enabling the rapid screening of antivenoms against a range of venoms.

5. Historically, the lethality of snake venoms has been based on murine LD50 studies. Due to ethical reasons, these studies are being superseded by in vitro studies. Instead, the time taken to produce 90% inhibition of nerve‐mediated twitches (i.e. t90) in skeletal muscle preparations can be determined. However, these two procedures result in different rank orders because they are measuring two different parameters. While murine LD50 determinations are based on ‘quantity’, t90 values are based on how ‘quick’ a venom acts. Therefore, knowledge of both parameters is still desirable.

6. In vitro neuromuscular preparations have proven to be invaluable tools in the examination of snake venoms and isolated neurotoxins. They will continue to play a role in further elucidating the mechanism of action of these highly potent toxins. Further study of these toxins may provide more highly specific research tools or lead compounds for pharmaceutical agents.
Abnormality in fibre type distribution of soleus and plantaris muscles in non‐obese diabetic Goto‐Kakizaki rats
Authors: Yasuda Koichiro , Nishikawa Waka , Iwanaka Nobumasa , Nakamura Eitaro , Seino Yutaka , Tsuda Kinsuke , Ishihara Akihiko
Published: March 2003

1. Fibre type distributions of the slow soleus and fast plantaris muscles were investigated in 5‐, 9‐ and 20‐week‐old male Goto‐Kakizaki (GK) rats, as an animal model of non‐obese diabetes, and were compared with those of age‐matched non‐diabetic Wistar rats.

2. Bodyweight and both soleus and plantaris muscle weights were lower in GK rats than in Wistar rats, regardless of age. In addition, both relative soleus and plantaris muscle weights per bodyweight were lower in GK rats than in Wistar rats, regardless of age.

3. In the soleus muscle, a higher percentage of type I fibres and a lower percentage of type IIA fibres were observed in 5‐ and 9‐week‐old GK rats. In addition, there were no type IIA fibres in 20‐week‐old GK rats.

4. In the plantaris muscle, there were no differences in fibre type distribution of 5‐week‐old GK rats. However, a higher percentage of type IIB fibres and a lower percentage of type I and type IIA fibres were observed in 9‐ and 20‐week‐old GK rats. In addition, there were no type I fibres in 20‐week‐old GK rats.

5. These results indicate that the decreased percentage of high‐oxidative fibres (e.g. type IIA fibres in the soleus muscle and type I and type IIA fibres in the plantaris muscle) of the diabetic animals is concerned with an impairment in insulin sensitivity and glucose metabolism and is not related to bodyweight.
Roles and regulation of glutamate transporters in the central nervous system
Authors: O'Shea RD
Published: March 2003

1. Glutamate transporters (also known as excitatory amino acid transporters or EAAT) are solely responsible for the removal of the excitatory neurotransmitter l‐glutamate (Glu) from the extracellular space and, thus, permit normal transmission, as well as preventing cell death due to the excessive activation of Glu receptors.

2. Five subtypes of glutamate transporter (EAAT1–5) exist, possessing distinct pharmacology, cellular localization and modulatory mechanisms.

3. Experimental inhibition of EAAT activity in vitro and in vivo results in increased extracellular concentrations of Glu and in neuronal death via excitotoxicity, highlighting the importance of EAAT in normal excitatory neurotransmission.

4. Dysfunction of EAAT may contribute to the pathology of both acute neuronal injury and chronic neurodegenerative conditions, so correction of EAAT function under these conditions may provide a valuable therapeutic strategy.

5. The present review describes basic pharmacological studies that allow new insights into EAAT function and suggest possible strategies for the therapeutic modulation of EAAT.
Effects of the angiotensin‐converting enzyme inhibitor alacepril on exercise capacity and neurohormonal factors in patients with mild‐to‐moderate heart failure
Authors: Kinugawa Toru , Osaki Shuichi , Kato Masahiko , Ogino Kazuhide , Shimoyama Masaki , Tomikura Yoko , Igawa Osamu , Hisatome Ichiro , Shigemasa Chiaki
Published: March 2003

1. Alacepril is a long‐acting, sulphydryl‐containing angiotensin‐converting enzyme inhibitor. Data are limited regarding the effects of alacepril on exercise tolerance in patients with chronic heart failure (CHF). The aim of the present study was to determine the effects of chronic alacepril treatment on exercise capacity and neurohormones in patients with CHF.

2. The effects of 12 weeks treatment with alacepril on clinical, echocardiographic and cardiopulmonary exercise variables were studied in 18 CHF patients (mean age: 63 ± 2 years; New York Heart Association (NYHA) class I n = 6, class II n = 10, class III n = 2) in a cross‐over fashion. Resting levels of plasma noradrenaline, renin–angiotensin system activity and natriuretic peptides were evaluated.

3. Treatment with alacepril significantly improved NYHA functional class and decreased cardiothoracic ratio (60.1 ± 2.0 vs 58.1 ± 1.9% for baseline vs alacepril, respectively; P < 0.01). Cardiac dimensions by echocardiogram were decreased after alacepril therapy. Peak Vo2 (17.7 ± 1.2 vs 19.5 ± 1.3 mL/min per kg; P < 0.01) and anaerobic threshold (11.7 ± 0.6 vs 13.2 ± 0.9 mL/min per kg; P < 0.01) increased with alacepril treatment. Plasma noradrenaline and plasma angiotensin II levels were not altered, but plasma aldosterone (77.7 ± 13.5 vs 51.7 ± 9.7 pg/mL; P < 0.01), atrial natriuretic peptide (ANP; 86.5 ± 20.3 vs 43.6 ± 7.6 pg/mL; P < 0.05) and brain natriuretic peptide (BNP; 222.7 ± 59.3 vs 117.7 ± 34.3 pg/mL; P < 0.05) levels decreased after alacepril treatment.

4. These results suggest that treatment with alacepril improves functional status and exercise capacity in patients with mild‐to‐moderate CHF. Neurohormones were favourably influenced by alacepril therapy, with significant decreases in plasma aldosterone, ANP and BNP levels.
Antihyperglycaemic effect of Cassia auriculata in experimental diabetes and its effects on key metabolic enzymes involved in carbohydrate metabolism
Authors: Latha Muniappan , Pari Leelavinothan
Published: March 2003

1. In experimental diabetes, enzymes of glucose and fatty acid metabolism are markedly altered. Persistent hyperglycaemia is a major contributor to such metabolic alterations, which lead to the pathogenesis of diabetic complications. To our knowledge, there are no available reports on the enzymes of hepatic glucose metabolism of Cassia auriculata flower against diabetes. The present study was designed to study the effect of Cassia auriculata flower extract (CFEt) on hepatic glycolytic and gluconeogenic enzymes.

2. Streptozotocin diabetic rats were given CFEt (0.15, 0.30 and 0.45 g/kg) or 600 µg/kg glibenclamide for 30 days. At the end of 30 days, blood glucose, plasma insulin, haemoglobin, glycosylated haemoglobin, glycolytic and gluconeogenic enzymes were assessed.

3. Administration of CFEt at 0.45 g/kg significantly decreased blood glucose, glycosylated haemoglobin and gluconeogenic enzymes and increased plasma insulin, haemoglobin and hexokinase activity. Similarly, administration of glibenclamide showed a significant effect; however, CFEt at 0.15 and 0.30 g/kg did not show any significant effect.

4. In conclusion, the observations show that the aqueous extract of CFEt possesses an antihyperglycaemic effect and suggest that enhanced gluconeogenesis during diabetes is shifted towards normal and that the extract enhances the utilization of glucose through increased glycolysis. The effect of CFEt was more prominent than that of glibenclamide.
Lens formation by pigmented epithelial cell reaggregate from dorsal iris implanted into limb blastema in the adult newt
Authors: Ito Mayumi , Hayashi Toshinori , Kuroiwa Atsushi , Okamoto Mitsumasa
Published: March 2003

In newt lens regeneration, the dorsal iris has lens forming ability and the ventral iris has no such capability, whereas there is no difference in the morphological criteria. To investigate the real aspects of this characteristic lens regeneration in the newt at the cellular level, a useful model system was constructed by transplanting the dorsal and ventral reaggregate derived from singly dissociated pigmented epithelial cells of the iris into the blastema of the forelimb in the newt. The lens was formed from the dorsal reaggregate with high efficiency, but not from the ventral one. No lens formation was observed in the implantation of the reaggregate into the tissue of the intact limbs. In detailed examination of the process of lens formation from the reaggregate, it was shown that tubular formation was the first step in the rearrangement of cells within the reaggregate. This was followed by depigmentation, vesicle formation with active cell growth, and the final step was lens fiber formation by transdifferentiation of epithelial cells composing the lens vesicle. The process was almost the same as in situ lens regeneration except the reconstitution of the two‐layered epithelial structure was embodied as flattened tubular formation in the first step. The present study made it possible for the first time to examine lens forming ability in the reaggregate mixed with dorsal and ventral cells, because the formation of a reaggregate was started from singly dissociated cells of the dorsal and ventral cells of the iris. Mixed reaggregate experiments indicated that the existence of the dorsal cells in a cluster within the reaggregate is important in lens formation, and ventral cells showed an inhibitory effect on the formation. The present study demonstrated that the limb system thus constructed was effective for the analysis of lens formation at the cellular level and made it possible to examine the role of dorsal and ventral cells in lens regeneration.