bluuebunny/crossref_metadata_2025 huggingface dataset:
Dobutamine induces ineffective work in regional ischaemic myocardium: an experimental strain rate imaging study
Authors: WEIDEMANN Frank , BROSCHEIT Jens , EBERBACH Nicole , STEENDIJK Paul , VOELKER Wolfram , GREIM Clemens , ERTL Georg , ROEWER Norbert , STROTMANN Jörg M
Published: January 2004

In the present study, we sought to investigate the effects of differing inotropic conditions on regional myocardial function in ischaemic segments. In an experimental pig model (n=11), the regional deformation parameters peak systolic strain rate [SRSYS (peak velocity of thickening)], systolic strain [εSYS (systolic wall thickening)] and post-systolic strain [εPST (ongoing wall thickening after end of systole)] were measured during normal perfusion and regional ischaemia of the posterior wall. These parameters were compared with global contractility [EES (end-systolic elastance)] measured by a conductance catheter. Ischaemia was induced by an active coronary hypoperfusion in the circumflex coronary artery. Measurements were done at baseline, during dobutamine and during esmolol infusion. In normal perfused hearts, SRSYS (4.8±0.2 s-1 at baseline) increased during dobutamine infusion, decreased during esmolol infusion and correlated significantly with global EES. In addition, εSYS averaged 93±3% at baseline and there was almost no εPST (4±1%) in normal myocardium. In ischaemic myocardium, SRSYS and εSYS were significantly reduced compared with normal myocardium at baseline (SRSYS=2.8±0.3 s-1, and εSYS=43±6%; P<0.001 compared with normal perfused hearts), whereas global EES was unchanged. In contrast, εPST was significantly increased in regional ischaemic segments compared with the non-ischaemic myocardium (15±2%; P<0.001). During the dobutamine infusion, SRSYS remained unchanged. In contrast, εSYS decreased (25±5%; P<0.001) and εPST increased (25±4%; P<0.05) significantly during dobutamine infusion in ischaemic myocardium. In ischaemic segments, an inotropic stimulation with dobutamine resulted in a shift of strain from systole (εSYS) to post-systole (εPST). Thus dobutamine induced ineffective myocardial work in ischaemic segments.
Creatine supplementation increases glycogen storage but not GLUT-4 expression in human skeletal muscle
Authors: LOON Luc J. C. VAN , MURPHY Robyn , OOSTERLAAR Audrey M. , CAMERON-SMITH David , HARGREAVES Mark , WAGENMAKERS Anton J. M. , SNOW Rodney
Published: January 2004

It has been speculated that creatine supplementation affects muscle glucose metabolism in humans by increasing muscle glycogen storage and up-regulating GLUT-4 protein expression. In the present study, we assessed the effects of creatine loading and prolonged supplementation on muscle glycogen storage and GLUT-4 mRNA and protein content in humans. A total of 20 subjects participated in a 6-week supplementation period during which creatine or a placebo was ingested. Muscle biopsies were taken before and after 5 days of creatine loading (20 g·day-1) and after 6 weeks of continued supplementation (2 g·day-1). Fasting plasma insulin concentrations, muscle creatine, glycogen and GLUT-4 protein content as well as GLUT-4, glycogen synthase-1 (GS-1) and glycogenin-1 (Gln-1) mRNA expression were determined. Creatine loading significantly increased total creatine, free creatine and creatine phosphate content with a concomitant 18±5% increase in muscle glycogen content (P<0.05). The subsequent use of a 2 g·day-1 maintenance dose for 37 days did not maintain total creatine, creatine phosphate and glycogen content at the elevated levels. The initial increase in muscle glycogen accumulation could not be explained by an increase in fasting plasma insulin concentration, muscle GLUT-4 mRNA and/or protein content. In addition, neither muscle GS-1 nor Gln-1 mRNA expression was affected. We conclude that creatine ingestion itself stimulates muscle glycogen storage, but does not affect muscle GLUT-4 expression.
Short- and long-term reproducibility of autonomic measures in supine and standing positions
Authors: KOWALEWSKI M. A. , URBAN M.
Published: January 2004

Autonomic nervous tests and heart rate variability (HRV) have been used to assess cardiac autonomic function and to evaluate long-term prognosis. The aim of this study was to evaluate the short- and long-term reproducibility of HRV parameters and autonomic nervous tests according to body position (supine or standing). The study group consisted of 26 healthy subjects. Autonomic nervous tests and HRV were performed twice during the day and the results were averaged. The protocol was then repeated 3 days after each examination and also after 6 and 24 months. Autonomic nervous tests included deep breathing, Valsalva manoeuvre and isometric muscle exercise (handgrip), as well as blood pressure and heart rate in response to standing. ECG recordings were taken for 10 min during spontaneous breathing for HRV analysis. We found that the reproducibility of some parameters of the autonomic nervous test were independent of body position [E/I ratio (heart rate response to deep breathing)], whereas other parameters were dependent on body position (Valsalva manoeuvre and blood pressure response to sustained handgrip). In addition, within-day measurements of those parameters varied from non-reproducible (Valsalva ratio, handgrip and blood pressure response to standing) to moderately reproducible [E/I ratio and 30/15 ratio (heart rate response to standing)]. Among the HRV parameters, we found that total power (TP), low (LF)- and high (HF)-frequency were reproducible not only for measurements made within the same day, but also during short- and long-term observations, and only the LF/HF ratio was dependent on body position. We conclude that only a few autonomic nervous tests are reproducible in the short- and long-term. Because HRV parameters obtained during spontaneous respiration showed high reproducibility for measurements made within the same day as well as in the short- and long-term, they should be used instead of autonomic nervous tests when long-term observations are carried out in a healthy population.
Vigorous response in plasma N-terminal pro-brain natriuretic peptide (NT-BNP) to acute myocardial infarction
Authors: GILL Denzil , SEIDLER Timothy , TROUGHTON Richard W. , YANDLE Timothy G. , FRAMPTON Christopher M. , RICHARDS Mark , LAINCHBURY John G. , NICHOLLS Gary
Published: January 2004

Acute myocardial infarction (MI) results in activation of neurohormonal systems and increased plasma concentrations of myocardial enzymes and structural proteins. We hypothesized that plasma levels of N-terminal pro-brain natriuretic peptide (NT-BNP) would respond more vigorously after MI than those of other natriuretic peptides. We also sought to compare this response with that of the established myocardial injury markers troponin T (TnT), myoglobin and creatine kinase MB (CK-MB). We obtained multiple blood samples for measurement of atrial natriuretic peptide (ANP), N-terminal pro-ANP, brain natriuretic peptide (BNP) and NT-BNP along with CK-MB, TnT and myoglobin in 24 patients presenting to the Coronary Care Unit within 6 h of onset of MI. Multiple samples were obtained in the first 24 h, then at 72 h, 1 week, 6 weeks and 12 weeks. NT-BNP increased rapidly to peak at 24 h and exhibited greater (P<0.001) absolute increments from baseline compared with BNP and ANP, whereas NT-ANP did not change from baseline. Proportional increments in NT-BNP were also greater than those for the other natriuretic peptides (P<0.05). Natriuretic peptide levels reached their peak around 24 h, later than peak TnT, CK-MB and myoglobin (peak between 1–10 h), and NT-BNP and ANP remained elevated on average for 12 weeks. Our present results, with detailed sampling of a cohort of acute MI patients, demonstrate greater absolute and proportional increments in NT-BNP than ANP or BNP with sustained elevation of these peptides at 12 weeks.
Erythropoietin response after correction of severe hypoxaemia due to acute respiratory failure in chronic obstructive pulmonary disease patients
Authors: PAVLISA Gordana , VRBANIC Veljko , KUSEC Vesna , JAKSIC Branimir
Published: January 2004

In order to determine the initial values and dynamic changes of EPO (erythropoietin) after therapy, 57 consecutively presenting, typical COPD (chronic obstructive pulmonary disease) patients with chronic hypoxia and acute exacerbated serum EPO levels were serially measured. Initial mean EPO levels were slightly above the normal range (41.4±83.5 units/l), but in the majority of patients the initial EPO levels were significantly reduced. Following the correction of hypoxaemia, mean EPO levels decreased to 14.1±16.9 units/l (P=0.0093). However, not all COPD patients showed this pattern; in an important subset of patients (36.8%), who had initially lower EPO levels and lower erythrocyte count, EPO levels were significantly increased (by more than 60%; P=0.0028) on the second day of treatment, despite correction of the hypoxaemia. This finding was unexpected and paradoxical when compared with physiological studies addressing the same issue. The data presented support previous reports of variable EPO levels in severely hypoxic COPD patients and suggest that the haematological response is already hampered at an early stage, at the level of EPO production, and much less likely at later steps in the haemopoietic response by failure to respond to elevated EPO levels. Our data are consistent with recent discoveries that the O2 sensing and regulation of EPO production is a complex process in which multiple factors, including cytokines and therapeutic agents, play a role by enhancing or inhibiting the response. We believe that further studies on this clinical condition are complementary to basic physiological research and may help to elucidate the role of cytokines and other individual factors in complex clinical hypoxic situations.
Effects of dietary supplementation with arachidonic acid on platelet and renal function in patients with cirrhosis
Authors: PANTALEO Pietro , MARRA Fabio , VIZZUTTI Francesco , SPADONI Saura , CIABATTONI Giovanni , GALLI Claudio , VILLA Giorgio LA , GENTILINI Paolo , LAFFI Giacomo
Published: January 2004

Advanced cirrhosis is associated with reduced platelet function and altered renal function and sodium handling. Arachidonic acid (AA) metabolites contribute to platelet aggregation and to maintain the response to diuretics in advanced cirrhosis. In the present study, we tested the effects of a dietary supplementation for 8 weeks with a triacylglycerol (triglyceride) enriched in AA (ARASCO®; 4 g/day) or oleic acid (OA) on plasma and membrane fatty acid composition, platelet aggregation and renal prostaglandin (PG) metabolism. At baseline, all patients had reduced platelet aggregation. Patients treated with AA showed a significant increase in the percentage of AA in plasma lipids and membrane phospholipids. These changes were associated with an increased platelet aggregation in response to collagen (from 55.83±20.63 to 67.67±14.44%; P<0.05). At baseline, all urinary AA metabolites, including PGE2, 6-keto-PGF1α, 8-epi-PGF2α and 11-dehydro-thromboxane B2, were elevated in cirrhotic patients when compared with a group of normal subjects. After furosemide treatment, urinary excretion of 11-dehydro-thromboxane B2 increased significantly. Supplementation with AA did not result in any significant change in urinary PG excretion either before or after diuretic administration. The results of the present study show that dietary supplementation with AA effectively increases the levels of this fatty acid in plasma and membrane phospholipids and improves platelet aggregation. These data suggest a possible novel approach to the treatment of the haemostatic defect observed in these patients.
Aspirin inhibits endothelial nitric oxide synthase (eNOS) and Flk-1 (vascular endothelial growth factor receptor-2) prior to rat colon tumour development
Authors: ESCRIBANO Marta , MOLERO Laura , LÓPEZ-FARRÉ Antonio , ABARRATEGUI Cynthia , CARRASCO Carolina , GARCÍA-MENDEZ Antonio , MANZARBEITIA Félix , MARTÍN María Jesús , VÁZQUEZ Marian , SÁNCHEZ-FAYOS Paloma , RICO Luis , CUBERO Juan Carlos PORRES
Published: January 2004

Formation of blood vessels is a fundamental element in the control of tumour growth in which vascular endothelial growth factor (VEGF) and nitric oxide (NO) have been demonstrated to be involved. Our aim was to analyse whether changes in the expression of endothelial NO synthase (eNOS) and VEGF in colonic tissue could be detected early and even before the identification of colon tumour-associated morphological modifications in azoxymethane-treated rats. We studied further whether aspirin treatment changed these parameters. An increased expression of both eNOS and VEGF in colonic tissue from azoxymethane-treated rats compared with that from control rats was found. Aspirin treatment (10 mg/kg of body weight per day) reduced eNOS expression, but failed to modify the expression of VEGF in the colonic tissue of azoxymethane-treated rats. No evidence of aberrant crypt formation or changes in the number of blood vessels were observed in the colon of any of the animals studied. Expression of the VEGF receptor Flk-1, but not Flt-1, was increased in colonic tissue of azoxymethane-treated rats compared with control rats. The expression of Flk-1 was mainly localized in the epithelial cells, particularly in the lower part of the crypt. Aspirin treatment reduced Flk-1 expression in both control and azoxymethane-treated rats. Caspase-3 activity, which has been considered as an apoptotic index, was almost undetectable in azoxymethane-treated rats. Aspirin treatment stimulated caspase-3 activity. Overexpression of eNOS, VEGF and its receptor Flk-1 occurred early after azoxymethane administration in rat colonic tissue, even before morphological changes associated with tumour generation were observed, and aspirin prevented the overexpression of both eNOS and VEGF receptor Flk-1.
Coronary vasomotor response is related to the angiographic extent of coronary sclerosis in patients with stable angina pectoris
Authors: ASSELBERGS Folkert W. , MONNINK Stefan H.J. , VEEGER Nic J.G.M. , BOVEN Ad J. VAN , HAELST Paul L. VAN , JESSURUN Gillian A.J. , VAN GILST Wiek H. , TIO René A.
Published: January 2004

Disturbed vasomotor function in coronary arteries has clinical importance in early stages of coronary artery disease (CAD), as it may contribute to the potential risk for an ischaemic coronary event. In the present study, we have investigated the relationship between coronary vasomotor function and the extent of CAD. The response to acetylcholine and nitrate infusion was assessed by quantitative coronary angiography. The extent of CAD was categorized into two groups: minor CAD (normal coronary arteries and vessel wall irregularities) and significant CAD (one-, two- and three-vessel disease). A total of 277 patients with stable angina pectoris, referred for a first diagnostic coronary angiography, were eligible for analysis (mean age 57 years, 61% male). The response to nitrate was significantly impaired in patients with significant CAD (P<0.001). On the other hand, the response to acetylcholine was not different between the two groups (P=0.12); however, a trend between the response to acetylcholine and the extent of CAD was observed in patients without a previous infarction (P=0.07), which was a significant interaction variable. Furthermore, a significant relationship between coronary vasomotor response and the number of cardiovascular risk factors was observed (P<0.05). In conclusion, in a heterogeneous group of patients, coronary vasomotor function measured by nitrate infusion was more strongly associated with the extent of CAD and the number of risk factors than the response to acetylcholine. These data suggest that, in patients with advanced atherosclerosis or multiple risk factors, the vasomotor dysfunction is not solely restricted to the endothelium.
Peripheral cholinergic function in humans with chronic fatigue syndrome, Gulf War syndrome and with illness following organophosphate exposure
Authors: KHAN Faisel , KENNEDY Gwen , SPENCE Vance A. , NEWTON David J. , BELCH Jill J. F.
Published: January 2004

In the present study, we have investigated whether the peripheral cholinergic abnormalities that we have reported previously [Spence, Khan and Belch (2000) Am. J. Med. 108, 736–739] in patients with chronic fatigue syndrome (CFS) are also present in those with Gulf War syndrome (GWS) and agricultural workers exposed to organophosphate pesticides, where cholinesterase inhibition is specifically implicated. We also looked at whether these abnormalities might be due to a reduction in the activity of cholinesterase expressed on the vascular endothelium. We used laser Doppler imaging to measure the forearm skin blood flow responses to iontophoresis of acetylcholine and of methacholine (which is resistant to breakdown by cholinesterase) in patients with CFS, GWS and those with a history of ill health after definite organophosphate exposure, as well as in matched healthy controls. The response to acetylcholine was significantly higher in patients with CFS than in controls (P=0.029, repeated-measures ANOVA), but was normal in those with GWS and those exposed to organophosphates. The methacholine response was higher than the acetylcholine response in all patient groups except for those with CFS, where there was no difference between the responses. Although there are many clinical similarities between these three illnesses, our results indicate peripheral cholinergic abnormalities in the vascular endothelium of only patients with CFS, suggesting that this syndrome has a different aetiology, which might involve inhibition of vascular cholinesterase.
Effect of ascorbate on serum lipids and urate metabolism during exhaustive training
Authors: YANAI Hidekatsu , MORIMOTO Mie
Published: January 2004

Physical activity is associated with beneficial changes in serum lipids, but exhaustive exercise has been suggested to increase oxidative stress. To test the effect of ascorbate (vitamin C) on serum lipids and the metabolism of urate, which is the most important intrinsic antioxidant, during exhaustive exercise, we performed a randomized, blinded, placebo-controlled study on eight male well-trained athletes. subjects were randomly allocated to either a group given 1000 mg of ascorbate daily (n=4) or a placebo group (n=4). Fasting serum lipids and urate concentrations were measured before and after 3 weeks of training. Although serum low-density lipoprotein (LDL)-cholesterol levels decreased and high-density lipoprotein (HDL)-cholesterol levels increased significantly in the ascorbate group after the 3 weeks of training, serum LDL-cholesterol levels increased and HDL-cholesterol levels decreased significantly in the placebo group. Furthermore, serum urate levels were elevated significantly in the placebo group; however, these levels did not change in the ascorbate group. When compared with the placebo group, significantly higher serum HDL-cholesterol and lower serum LDL-cholesterol and urate levels were observed in the ascorbate group after training. In conclusion, our results suggested that ascorbate may contribute to the desirable changes in serum lipids during exhaustive training and suggest the significant association between ascorbate and urate under intense training.
Early programming of weight gain in mice prevents the induction of obesity by a highly palatable diet
Authors: OZANNE Susan E. , LEWIS Rohan , JENNINGS Bridget J. , Nicholas HALES C.
Published: January 2004

Poor early growth is associated with Type II diabetes, hypertension and other features of the metabolic syndrome in adulthood. It has been suggested that this results from the development of a thrifty phenotype by a malnourished fetus. Such a phenotype would predispose the offspring to the development of obesity if born into conditions of over-nutrition. The present study aimed to determine if early nutrition affected subsequent development of obesity. Mice were established as follows: (a) controls (offspring of control dams), (b) recuperated (offspring of dams fed a low-protein diet during pregnancy, but nursed by control dams) and (c) postnatal low-protein (offspring of control dams nursed by low-protein-fed dams). Mice were weaned on to standard laboratory chow or a cafeteria diet. Recuperated offspring, although smaller at birth (P<0.01), caught up and exceeded the weight of control offspring by 7 days of age (P<0.001). Postnatal low-protein offspring were smaller than controls by 7 days of age (P<0.001). Recuperated animals gained more weight than controls when given free access to a highly palatable diet (P<0.01). Postnatal low-protein animals showed no additional weight gain when given a highly palatable diet compared with chow-fed litter-mates. These results suggest that the early environment has long-term consequences for weight gain. These programmed responses are powerful enough to block excess weight gain from a highly palatable diet and, thus, have major implications for the drug-free regulation of food intake and obesity.
Effects of delayed preconditioning on myocardial regional contractility during repeated episodes of low-flow ischaemia in anaesthetized dogs: possible role of nitric oxide
Authors: SZIGETI Zsolt , SIMON Kornél , PARRATT James R. , VÉGH Ágnes
Published: January 2004

The effect of cardiac pacing on repeated low-flow ischaemia-induced changes in regional myocardial segmental contractility, and the role in these changes of nitric oxide, were investigated in anaesthetized dogs. Dogs were instrumented for cardiac pacing (pacing electrode in the right ventricle). Dogs were paced (four times for 5 min; pacing rate 220 beats·min-1) 24 h prior to the repeated ischaemic insults. Controls were instrumented, but not paced. After 24 h, the dogs were re-anaesthetized with pentobarbitone and subjected to four 20 min low-flow ischaemia and reperfusion cycles, by constricting the left anterior descending coronary artery (LAD) to achieve an approx. 50% reduction in resting coronary blood flow. In some dogs (both control and paced), NG-nitro-L-arginine methyl ester (L-NAME; a non-selective inhibitor of nitric oxide synthase) was infused into a side-branch of the LAD 10 min prior to the first ischaemia/reperfusion cycle. Regional contractile function was measured by ultrasonic microcrystals in the ischaemic and normal regions of the left ventricular wall supplied from the LAD and left circumflex coronary artery respectively, and expressed as percentage changes in segmental shortening (%SS). In some dogs, myocardial tissue blood flow (coloured microspheres) and lactate production (local coronary venous sampling) were measured; samples were also taken for histological analysis. In control dogs, the regional %SS was progressively reduced within the ischaemic segment during the four repeated occlusions (by 40±6, 59±6, 68±6, 70±6% during occlusions 1–4 respectively). These reductions were more pronounced, especially during the first two cycles (68±6, 68±6, 67±6, 67±6%, respectively), when the dogs had been previously subjected to cardiac pacing. In both paced and control dogs, these changes in contractile function were L-NAME-sensitive. Thus, in the presence of L-NAME, changes in regional segmental shortening in control dogs were 37±8, 40±8, 37±8, 42±11% and in the paced dogs 46±6, 45±7, 45±8, 45±7% respectively, during the four consecutive occlusions. There were no significant differences in tissue blood flow or in lactate production between the groups, and no structural changes indicative of infarction. These results show that the myocardium rapidly adapts to re-occurring acute ischaemia by reducing contractility within the ischaemic segment and, thereby, metabolic demand. Furthermore, cardiac pacing 24 h prior to these ischaemic challenges induces a similar adaptive response, a form of ‘delayed preconditioning’. Since both the acute and delayed adaptation were L-NAME-sensitive, we suggest that this adaptation involves nitric oxide.
Protein, programming and plumpness: is there a link?
Authors: HUXLEY Rachel R.
Published: January 2004

Early-life nutrition has been suggested to influence the progression of chronic disease. In this issue of Clinical Science, Ozanne and colleagues argue that the pre- and post-natal diet can have a significant impact on the risk of becoming overweight in later life. Although an intriguing finding that warrants further investigation, it is most likely that the key to stemming the obesity pandemic will depend chiefly on the implementation of effective population-wide strategies that focus on lifestyle modification, both in childhood and in adult life.
The Influence of Opioid Peptides on Steroidogenesis in Porcine Granulosa Cells
Authors: Kaminski T , Siawrys G , Bogacka I , Okrasa S , Przala J
Published: January 2004

Contents

The present studies were undertaken to examine the influence of μ (β‐endorphin, DAMGO, FK 33‐824), δ (met‐enkephalin, leu‐enkephalin, DPLPE) and κ opioid receptor agonists (dynorphin A, dynorphin B, U 50488) used at different doses (1–1000 nm) alone and in combination with LH (100 ng/ml) on steroidogenesis in porcine granulosa cells derived from large follicles. The effects of μ, δ and κ receptor agonists on both basal and LH‐induced progesterone (P4) secretion were negligible. Agonists of μ opioid receptors reduced basal androstenedione (A4), testosterone (T) and oestradiol (E2) release. Co‐treatment with LH entirely abolished the inhibitory effect of these agonists on A4 and E2 secretion and resulted in an increase in T release. The addition of δ receptor agonists was followed by a decrease in basal A4, T and E2 secretion. The cells incubated in the presence of LH increased the androgen production and abrogated the inhibitory effect of δ agonists on E2 output. Basal A4, T and E2 release was also suppressed by κ receptor agonists. The presence of LH in culture media extended the inhibitory effect of these opioids on E2 output and caused either abolition of the inhibitory influence of κ agonists or even augmentation of both androgen release in response to the opioids. In conclusion, these data support the involvement of three major types of opioid receptors in the regulation of porcine granulosa cell steroidogenesis.
Expression of Occludin in Canine Testis and Epididymis
Authors: Gye MC
Published: January 2004

Contents

Tight junctions (TJ) in inter‐Sertoli junctional areas and epididymal epithelia are important for the formation of blood–testis barrier (BTB) and blood–epididymal barrier (BEB). In this study, the expression of occludin, an integral member of the TJ, was verified in canine testis and epididymis. Both low molecular weight (MW) (25–28 kDa) forms as well as high MW (68–72 kDa) forms of occludin were detected in the testis and epididymis using Western blot. The relative amount of the high MW forms of occludin vs low MW forms was higher in the testis than in the epididymis. Some difference in the composition of different MW forms of occludin was found along the segments of epididymis, suggesting the possible correlation between cellular composition of occludin proteins and paracellular permeability of epithelia along the epididymal tubule. In the testis, intense occludin immunoreactivity was found in the basally located inter‐Sertoli junctional area. Diffused immunoreactivity of occludin was also found in the cytoplasm of Sertoli cells. A similar pattern of zonula occludens‐1 immunoreactivity was found in the cytoplasm of Sertoli cells, suggesting that occludin was not confined to the inter‐Sertoli junctional areas and that subcellular localization of occludin in the Sertoli cells was dynamically regulated during spermatogenesis in canine testis. In the epididymis weak immunoreactivity was found in the apical sides and cytoplasm of epithelial cells.
Exposure to L‐Ascorbic Acid or α‐Tocopherol Facilitates the Development of Porcine Denuded Oocytes from Metaphase I to Metaphase II and Prevents Cumulus Cells from Fragmentation
Authors: Tao Y , Zhou B , Xia G , Wang F , Wu Z , Fu M
Published: January 2004

Contents

It is known that α‐tocopherol (vitamin E) and l‐ascorbic acid (vitamin C) can modulate many biochemical processes intracellularly or extracellularly as antioxidants. The objective of the present study was to investigate the effects of α‐tocopherol and l‐ascorbic acid on porcine oocyte meiotic maturation, viability and the functions of cumulus cells. In two independent experiments, porcine oocytes with or free from cumulus cells were exposed to different levels of α‐tocopherol (0, 10, 100 and 200 μm) or l‐ascorbic acid (0, 50, 250 and 750 μm). Cumulus expansion, cumulus cell DNA fragmentation, meiotic maturation and degeneration of oocytes were assessed 48 h after in vitro culture. The results showed that: (1) neither α‐tocopherol nor l‐ascorbic acid influenced cumulus expansion but both prevented cumulus cell DNA fragmentation. (2) α‐tocopherol lowered the percentage of denuded oocytes (DOs) arrested at germinal vesicle stage (GV). Among the oocytes undergoing germinal vesicle breakdown (GVBD) proportion, fewer DOs treated by α‐tocopherol were at metaphase I (MI) and more at metaphase II (MII). l‐ascorbic acid caused lower percentage of DOs arrested at GV stage and higher percentage of DOs undergoing GVBD, especially at MII. The influences of α‐tocopherol and l‐ascorbic acid were not obvious in cumulus‐enclosed oocytes (CEOs). (3) Both vitamins compromised the viability of CEOs and DOs. These results indicate that exposure to α‐tocopherol or l‐ascorbic acid promotes the development of porcine DOs from MI to MII and prevents cumulus cell DNA fragmentation at certain levels, especially 10 μmα‐tocopherol or 250 μml‐ascorbic acid.
On a modified Taylor–Dean stability problem where the small gap between the cylinders varies in the azimuthal direction
Authors: Eagles P. M.
Published: January 2004

We modify the classical Taylor–Dean stability problem to a case where the inner circular cylinder is rotating and the outer cylinder is fixed and noncircular in general. A method is given to determine some stability characteristics, in which the streamwise growth of a steady disturbance is calculated, in a small-gap approximation. Some particular examples are studied. If the gap width is increasing in the direction of flux of the basic steady-state flow, this flow is more unstable than for the case of constant gap width, and conversely when the gap width is decreasing.
A class of nonautonomous coupled KdV systems
Authors: Turhan Refik
Published: January 2004

A class of nonautonomous coupled Korteweg–de Vries (KdV) systems in (1+1) dimensions are considered for integrability classification. Integrability of the systems is associated with the existence of a certain recursion operator. Some new integrable nonautonomous two-component KdV systems are found.
Elliptic solitons and Gröbner bases
Authors: Brezhnev Yurii V.
Published: January 2004

We consider the solution of spectral problems with elliptic coefficients in the framework of the Hermite Ansatz. We show that the search for exactly solvable potentials and their spectral characteristics is reduced to a system of polynomial equations solvable by the Gröbner bases method and others. New integrable potentials and corresponding solutions of the Sawada-Kotera, Kaup-Kupershmidt, Boussinesq equations and others are found.
On the integration of products of Whittaker functions with respect to the second index
Authors: Becker Peter A.
Published: January 2004

Several new formulas are developed that enable the evaluation of a family of definite integrals containing the product of two Whittaker Wκ,μ(x)-functions. The integration is performed with respect to the second index μ, and the first index κ is permitted to have any complex value, within certain restrictions required for convergence. The method utilizes complex contour integration along with various symmetry relations satisfied by the Whittaker functions. The new results derived in this article are complementary to the previously known integrals of products of Whittaker functions, which generally treat integration with respect to either the first index κ or the primary argument x. A physical application involving radiative transport is discussed.
On the reduction and the existence of approximate analytic solutions of some basic nonlinear ODEs in mathematical physics and nonlinear mechanics
Authors: Panayotounakos Dimitrios E. , Sotiropoulos Nikolaos V.
Published: January 2004

Using series of admissible functional transformations we reduce the one-dimensional axisymmetric nonlinear Schrödinger (NLS) equation, as well as the forced damped nonlinear Duffing (NLD) equation to equivalent nonlinear first-order integrodifferential equations. The forced undamped (NLD) equation results as a special case. The reduced integrodifferential equations are exact. In the limits of small or large values of the parameters characterizing these nonlinear problems, we prove that further reductions lead to first-order nonlinear ordinary differential equations which, except in case of the (NLS) equation, are of the Abel classes. The approximate reduced (NLS) equation admits exact analytic solutions. On the other hand, taking into account the known exact analytic solutions of the equivalent Abel classes of equations we show that there do not exist analytic solutions of the above two nonlinear Duffing oscillators. However, if further asymptotic approximations take place, new approximate analytic solutions concerning the (NLD) equations are constructed.
Eigenvalues of Ruijsenaars–Schneider models associated with An−1 root system in Bethe ansatz formalism
Authors: Hou B. Y. , Sasaki R. , Yang W.-L.
Published: January 2004

Ruijsenaars–Schneider models associated with An−1 root system with a discrete coupling constant are studied. The eigenvalues of the Hamiltonian are given in terms of the Bethe ansatz formulas. Taking the “nonrelativistic” limit, we obtain the spectrum of the corresponding Calogero–Moser systems in the third formulas of Felder et al.
Topologically nontrivial quantum layers
Authors: Carron G. , Exner P. , Krejčiřı́k D.
Published: January 2004

Given a complete noncompact surface Σ embedded in R3, we consider the Dirichlet Laplacian in the layer Ω that is defined as a tubular neighborhood of constant width about Σ. Using an intrinsic approach to the geometry of Ω, we generalize the spectral results of the original paper by Duclos et al. [Commun. Math. Phys. 223, 13 (2001)] to the situation when Σ does not possess poles. This enables us to consider topologically more complicated layers and state new spectral results. In particular, we are interested in layers built over surfaces with handles or several cylindrically symmetric ends. We also discuss more general regions obtained by compact deformations of certain Ω.
Soret effect inducing subcritical and Hopf bifurcations in a shallow enclosure filled with a clear binary fluid or a saturated porous medium: A comparative study
Authors: Bourich M. , Hasnaoui M. , Mamou M. , Amahmid A.
Published: January 2004

Soret-driven thermosolutal convection within a shallow porous or fluid layer subject to a vertical gradient of temperature is investigated analytically and numerically. The bridging between a clear fluid and Darcy porous media problems is conducted using the Brinkman–Hazen–Darcy model in its transient form. The analytical solution is derived on the basis of the parallel flow approximation, and validated numerically using a finite difference method by solving the full governing equations. The study is focused on the thermal diffusion effects on the flow intensity, and on the heat and mass transfer rates. In particular, a comparative study is made for the two limiting cases that emerge from the present investigation, namely the low porosity Darcy porous medium and the clear fluid medium. The flow behavior for both cases is qualitatively similar. The critical Rayleigh numbers for the onset of subcritical, oscillatory and stationary convection are determined explicitly as functions of the governing parameters for infinite and finite layers. At the onset of instabilities, the wavenumber is equal to zero and the oscillation frequency vanishes at the onset of Hopf bifurcation. For a finite aspect ratio enclosure, the frequency is finite and decreases as the aspect ratio increases. The codimension-2 point exists and different flow regimes are delineated. For constant heat flux boundaries, only standing oscillatory and steady waves are found to exist. The analytical and numerical results are found to be in good agreement, within the range of the governing parameters considered in the present study. The thermal diffusion effect on the flow intensity and on the heat and mass transfer is more enhanced for Darcy medium compared to the clear fluid, for which the viscous effects are significant.
The influence of edge detection algorithms on the estimation of the fractal dimension of binary digital images
Authors: Ahammer Helmut , DeVaney Trevor T. J.
Published: January 2004

The boundary of a fractal object, represented in a two-dimensional space, is theoretically a line with an infinitely small width. In digital images this boundary or contour is limited to the pixel resolution of the image and the width of the line commonly depends on the edge detection algorithm used. The Minkowski dimension was evaluated by using three different edge detection algorithms (Sobel, Roberts, and Laplace operator). These three operators were investigated because they are very widely used and because their edge detection result is very distinct concerning the line width. Very common fractals (Sierpinski carpet and Koch islands) were investigated as well as the binary images from a cancer invasion assay taken with a confocal laser scanning microscope. The fractal dimension is directly proportional to the width of the contour line and the fact, that in practice very often the investigated objects are fractals only within a limited resolution range is considered too.
Transition elements for a non-Hermitian quadratic Hamiltonian
Authors: Swanson Mark S.
Published: January 2004

The non-Hermitian quadratic Hamiltonian H=ωa†a+αa2+βa†2 is analyzed, where a† and a are harmonic oscillator creation and annihilation operators and ω, α, and β are real constants. For the case that ω2−4αβ⩾0, it is shown using operator techniques that the Hamiltonian possesses real and positive eigenvalues. A generalized Bogoliubov transformation allows the energy eigenstates to be constructed from the algebra and states of the harmonic oscillator. The eigenstates are shown to possess an imaginary norm for a large range of the parameter space. Finding the orthonormal dual space allows the inner product to be redefined using the complexification procedure of Bender et al. for non-Hermitian Hamiltonians. Transition probabilities governed by H are shown to be manifestly unitary when the complexification procedure is followed. A specific transition element between harmonic oscillator states is evaluated for both the Hermitian and non-Hermitian cases to identify the differences in time evolution.
Construction of a family of quantum Ornstein–Uhlenbeck semigroups
Authors: Ko Chul Ki , Park Yong Moon
Published: January 2004

For a given quasi-free state on the CCR algebra over one dimensional Hilbert space, a family of Markovian semigroups which leave the quasi-free state invariant is constructed by means of noncommutative elliptic operators and Dirichlet forms on von Neumann algebras. The generators (Dirichlet operators) of the semigroups are analyzed and the spectrums together with eigenspaces are found. When restricted to a maximal Abelian subalgebra, the semigroups are reduced to a unique Markovian semigroup of classical Ornstein–Uhlenbeck process.
Eigenvalue problems of a two-dimensional Schrödinger operator with nonparabolic effective mass
Authors: Lin Wen-Wei , Shieh Shih-Feng
Published: January 2004

In this paper, we study the eigenvalue problem for the Schrödinger operator on a two dimensional disk with nonparabolic effective mass approximation. Here the effective mass depends on the energy states. Our results mainly concern with the number of energy states lying in a wire and the monotonicity of energy states with respect to the depth of the wire.
Differential contribution of avoidance and tolerance to dehydration resistance in populations of perennial ryegrass, Lolium perenne L.
Authors: Sugiyama Shuichi , Nikara Chikao
Published: January 2004

The mechanisms of a plant to resist water stress can be divided into 2 components: avoidance and tolerance. However, reliable methods for measuring these components have not been established. We qualitatively evaluated the avoidance and tolerance abilities of shoots in diploid and tetraploid populations of perennial ryegrass (Lolium perenne L.) by continuously measuring their water contents and mortality rates under severe dehydration stress. Plant age greatly influenced dehydration resistance. Younger (30 days old) plants showed lower resistance to dehydration stress than did older plants (60 days old) because of both their lower avoidance and tolerance abilities. The two populations showed contrasting patterns of response to dehydration stress. The tetraploid population (Condesa) had higher avoidance and lower tolerance than did the diploid population (Manhattan II), and different combinations of the 2 components resulted in similar degrees of resistance in the 2 populations. The results of experiments demonstrated the importance of distinction between avoidance and tolerance abilities for studies on plant water stress.
Statistical analysis of sheep CAT scan images using a Bayesian mixture model
Authors: Alston C. L. , Mengersen K. L. , Thompson J. M. , Littlefield P. J. , Perry D. , Ball A. J.
Published: January 2004

CAT scanning techniques are available to provide images that can aid in the assessment of carcass traits in live sheep during the course of animal experiments. In this paper we present a Bayesian formulation of an analysis that allows us to determine the composition of a scan in terms of proportions of the image attributable to fat, muscle (lean tissue), and bone. The technique, known as finite mixture modelling, also provides information about the distributional properties of some of these components, such as fat and bone. In the case of muscle, the analysis estimates several Gaussian distributions that combine to provide an approximation to its likelihood.The model is estimated through the use of the Gibbs sampler, with the distributional properties of carcass components being obtained from the resultant Markov chains.
Ovine antimicrobial peptides: new products from an age-old industry
Authors: Anderson Rachel C. , Wilkinson Brian , Yu Pak-Lam
Published: January 2004

Antimicrobial peptides are part of the natural immune system of all plants and animals. This review focusses on ovine antimicrobial peptides because of the importance of the lamb industry in Australasia. The epithelial tissue β-defensins, respiratory surfactant-associated anionic peptides (SAAPs), and neutrophil cathelicidins are all described, and possible applications for these peptides are looked at, including use in ovine medicine, as biopreservatives, and as human therapeutics.
The effects of addition of bauxite red mud to soil on P uptake by plants
Authors: Snars K. , Hughes J. C. , Gilkes R. J.
Published: January 2004

The chemical properties of red mud, a byproduct of Bayer process refining of bauxite to alumina, make disposal of the material problematic. It is very alkaline (pH > 11), contains a large amount of sesquioxides, and thus has a very high P retention capacity. These characteristics have encouraged its use as a soil amendment to enhance P retention in sandy soils. A glasshouse experiment was carried out to investigate the effect of red mud on plant-available P. Leached red mud (LRM) (pH 7.24) was mixed at rates of 0, 5, 10, and 20 t/ha with a very sandy soil, provided with a full basal fertiliser and various rates of phosphate, and then sown with perennial ryegrass. Five harvests were obtained over a period of 245 days. At the end of the experiment the highest rate of addition of LRM gave an increase in soil pH of less than one unit and the electrical conductivity had not changed substantially or systematically. Bicarbonate-extractable P (bic-P) had decreased considerably from the initial values. However, there were no significant differences between bic-P values at the different levels of red mud application for the same rate of P application. Plant yield was not significantly different between treatments. Addition of red mud (a) decreased the P concentration of plants for the same amount of P applied; and (b) required a larger amount of bic-P to maintain a constant level of P in the plant. The red mud had adsorbed both applied and existing P and reduced the plant availability of bic-P. The economic impact of these processes needs evaluation.
Identity and pathogenicity of Fusarium spp. isolated from wheat fields in Queensland and northern New South Wales
Authors: Akinsanmi O. A. , Mitter V. , Simpfendorfer S. , Backhouse D. , Chakraborty S.
Published: January 2004

To establish the identity of Fusarium species associated with head blight (FHB) and crown rot (CR) of wheat, samples were collected from wheat paddocks with different cropping history in southern Queensland and northern New South Wales during 2001. CR was more widespread but FHB was only evident in northern NSW and often occurred with CR in the same paddock. Twenty different Fusarium spp. were identified from monoconidial isolates originating from different plant parts by using morphology and species-specific PCR assays. Fusarium pseudograminearum constituted 48% of all isolates and was more frequently obtained from the crown, whereas Fusarium graminearum made up 28% of all isolates and came mostly from the head. All 17 Fusarium species tested caused FHB and all 10 tested caused CR in plant infection assays, with significant (P < 0.001) difference in aggressiveness among species and among isolates within species for both diseases. Overall, isolates from stubble and crown were more aggressive for CR, whereas isolates from the flag leaf node were more aggressive for FHB. Isolates that were highly aggressive in causing CR were those originating from paddocks with wheat following wheat, whereas those from fields with wheat following maize or sorghum were highly aggressive for FHB. Although 20% of isolates caused severe to highly severe FHB and CR, there was no significant (P < 0.32) correlation between aggressiveness for FHB and CR. Given the ability of F. graminearum to colonise crowns in the field and to cause severe CR in bioassays, it is unclear why this pathogen is not more widely distributed in Australia.