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Maximal Increase (maximal + increase)
Selected AbstractsChanges in reactivity of rat arteries subjected to dynamic stretchACTA PHYSIOLOGICA, Issue 1 2000Dvoretsky The effect of dynamic stretch on the reactivity of the rat tail and mesenteric artery segments was studied. Segments mounted on a myograph were stretched by a computer-controlled motorized micromanipulator. Dynamic stretch (1, 5 or 7 Hz) inhibited the artery constriction induced by noradrenaline (10 ,M), 5-hydroxytryptamine (0.7 ,M), or electrical field stimulation of intramural nerves. In contrast, dynamic stretch enhanced the tetrodotoxin-insensitive dilation induced by electrical field stimulation of noradrenaline-contracted arteries. Maximal increase of dilation evoked by electrical field stimulation (24.5 ± 5.0% in mesenteric and 50.3 ± 15.6% in the tail artery) was observed at a dynamic stretch-frequency of 5 Hz. An inhibitor of nitric oxide synthesis, NG -nitro- L -arginine (100 ,M), abolished the difference in reactivity between static and dynamic conditions. The results indicate that dynamic stretch of the arteries activates nitric oxide synthesis/secretion, thus reducing constrictor and increasing dilator responses to the stimuli used. [source] Effects of locomotor stimulation and protein synthesis inhibition on circadian rhythms in size changes of L1 and L2 interneurons in the fly's visual systemDEVELOPMENTAL NEUROBIOLOGY, Issue 11 2007Elzbieta Kula Abstract Axons of monopolar cell interneurons L1 and L2 in the first optic lobe (lamina) of the fly Musca domestica undergo cyclical changes in diameter. These axons swell during the day and shrink during the night. In addition, the axons' size depends on light conditions since they are largest in continuous light (LL), somewhat smaller under day/night (LD) conditions, and smallest under constant darkness (DD). In this study we found that sizes of both cells can further increase in free flying flies under LD conditions, while the visual stimulation alone does not have significant effect on the cross-sectional area of L1 and L2 axons. The stimulation of free flying had no effect on L1 and L2 sizes if it was performed at the beginning of subjective day in LL or DD. Our results indicate that a maximal increase in size of L1 and L2 is observed when stimulation of free flying is synchronized with a fly' daily peak of activity. We also found that protein synthesis is needed to increase size of monopolar cell axons during the day when they normally swell. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] Noninvasive Assessment of Coronary Flow Reserve in the Left Anterior Descending Artery by Transthoracic Echocardiography before and after StentingECHOCARDIOGRAPHY, Issue 8 2007Elie Chammas M.D., F.E.S.C. Background: Noninvasive assessment of coronary flow reserve in the left anterior descending artery (LAD) by transthoracic Doppler echocardiography (TTDE) has been already validated as a new method for determining the degree of stenosis over the proximal flow. Objectives: The aim of the study is to determine, by TTDE, the feasibility and the value of the coronary flow reserve (CFR) (defined as the maximal increase in coronary blood flow above its basal pressure for a given perfusion pressure when coronary circulation is maximally dilated) in the mid-to-distal LAD before and after percutaneous angioplasty and to demonstrate the early recovery of microvascular tone immediately after stenting. Methods: The study population consisted of 36 patients with significant isolated LAD stenosis (70,90%) identified by coronary angiography. CFR was recorded in the mid-to-distal LAD at rest and during hyperemia obtained after adenosine intravenous infusion before and after stenting. Results: Adequate visualization of the LAD was obtained in 25 out of 36 patients (70%). At rest the mean CFR was 1.5132 ± 0.33 (1.1,2.58). However, after stenting the mean CFR was significantly higher: 2.18 ± 0.55 (1.3,3.8), with P <0.01. Conclusions: CFR can be easily determined by TTE in approximately 70% of patients. Noninvasive Doppler echocardiography shows impaired CFR in patients with LAD disease. After stenting CFR is restored, demonstrating early recovery of microvascular tone. These results are comparable to those published in the same conditions. Larger series with a long-term follow-up may allow identifying patients at high risk for restenosis after stenting. [source] Enantioselective estrogenicity of o,p'-dichlorodiphenyltrichloroethane in the MCF-7 human breast carcinoma cell line,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2009Lumei Wang Abstract Research increasingly suggests that selectivity between enantiomers may exist in acute and chronic toxicological effects of chiral contaminants. In this study, we used the human breast carcinoma MCF-7 cell line to evaluate enantioselectivity of o,p'-dichlorodiphenyltrichloroethane (o,p'-DDT). Baseline separation of o,p'-DDT enantiomers was achieved on the Chiralcel® OJ chiral column by high-performance liquid chromatography, and the absolute configuration and optical rotation of the resolved enantiomers were further identified. Significant differences in estrogenic potential were observed between the two enantiomers of o,p'-DDT in the MCF-7 cell proliferation assay (i.e., the E-Screen assay) and the real-time quantitative polymerase chain reaction (PCR). In the E-Screen assay, the relative proliferative effect ratios of R -(,)- o,p'-DDT and S -(+)- o,p'-DDT were 89.4 and 27.9%, respectively, and the relative proliferative potency ratios were 0.1 and 0.001%, respectively. Compared to the solvent control, R -(,)- o,p'-DDT induced the maximal increase of 2.31-fold at a concentration of 10,6 mol/L, while S -(+)- o,p'-DDT at 10,5 mol/L induced the maximal increase of 1.65-fold in estrogenic biomarker pS2 mRNA level. The maximal down-regulation of the transcription levels of estrogen receptor a (ER,) and ER, by R -(,)- o,p'-DDT were 49 and 40% at the concentration of 10,6 mol/L, while those by S -(+)- o,p'-DDT were 24 and 26% at the concentration of 10,5 mol/L. The cell proliferation, the up-regulation of pS2, and the down-regulation of ER, and ER, gene expressions induced by the racemate and enantiomers of o,p'-DDT were all reversed by cotreatment with 10,6 mol/L ICI 182,780. Therefore, the enantioselective estrogenicity of o,p'-DDT was likely through the ER, and ER, signaling pathways. Results from this study suggest the need for considering enantioselectivity of chiral contaminants in chronic ecological toxicities. [source] Rapid categorization of achromatic natural scenes: how robust at very low contrasts?EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2005Marc J.-M. Abstract The human visual system is remarkably good at categorizing objects even in challenging visual conditions. Here we specifically assessed the robustness of the visual system in the face of large contrast variations in a high-level categorization task using natural images. Human subjects performed a go/no-go animal/nonanimal categorization task with briefly flashed grey level images. Performance was analysed for a large range of contrast conditions randomly presented to the subjects and varying from normal to 3% of initial contrast. Accuracy was very robust and subjects were performing well above chance level (, 70% correct) with only 10,12% of initial contrast. Accuracy decreased with contrast reduction but reached chance level only in the most extreme condition (3% of initial contrast). Conversely, the maximal increase in mean reaction time was ,,60 ms (at 8% of initial contrast); it then remained stable with further contrast reductions. Associated ERPs recorded on correct target and distractor trials showed a clear differential effect whose amplitude and peak latency were correlated respectively with task accuracy and mean reaction times. These data show the strong robustness of the visual system in object categorization at very low contrast. They suggest that magnocellular information could play a role in ventral stream visual functions such as object recognition. Performance may rely on early object representations which lack the details provided subsequently by the parvocellular system but contain enough information to reach decision in the categorization task. [source] Evaluation of a Novel Real-Time Continuous Glucose-Monitoring System for Use in CatsJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2010S. Moretti Background: The Guardian REAL-Time is a continuous glucose-monitoring system (CGMS) recently developed to provide instantaneous interstitial glucose concentrations; the system does not require a monitor being fixed to the animal. Hypothesis: The CGMS provides accurate and reproducible real-time readings of glucose concentration in cats. Animals: Thirty-two diabetic cats, 2 cats with suspected insulinoma, and 5 healthy cats. Methods: Prospective, observational study. CGMS accuracy was compared with a reference glucose meter at normal, high, and low blood glucose concentrations using error grid analysis. Reading variability of 2 simultaneously used CGMS was determined in diabetic cats by calculating correlation and percentage of concordance of paired data at different glycemic ranges. The time interval between increasing glycemia and a rise in interstitial fluid glucose measured by the CGMS was assessed in healthy cats receiving glucose IV; the time point of maximal increase in interstitial glucose concentrations was calculated. Results: The CGMS was 100, 96.1, and 91.0% accurate at normal, high, and low blood glucose concentrations. Measurements deviated from reference by ,12.7 ± 70.5 mg/dL at normal, ,12.1 ± 141.5 mg/dL at high, and ,1.9 ± 40.9 mg/dL at low glucose concentrations. Overall, paired CGMS readings correlated significantly (r= 0.95, P < .0001) and concordance was 95.7%. The median delay after IV administration of glucose to an increase in interstitial glucose was 11.4 minutes (range: 8.8,19.7 minutes). Conclusions and Clinical Importance: Although some readings substantially deviated from reference values, the CGMS yields reproducible results, is clinically accurate in cats with hyperglycemia and euglycemia, and is slightly less accurate if blood glucose concentrations are low. Rapidly increasing interstitial glucose after a glycemic rise suggests that the CGMS is suitable for real-time measurement under clinical conditions. [source] Pharmacokinetics and pharmacodynamic effects of ABT-627, an oral ETA selective endothelin antagonist, in humansBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 6 2000Marianne C. Verhaar Aims, Endothelins (ETs) may play a role in the pathogenesis of a variety of cardiovascular diseases. The present study was designed to investigate the pharmacokinetic and pharmacodynamic effects of the orally active ETA selective receptor antagonist ABT-627 in healthy humans. Methods, Healthy volunteers were included in two studies with cross-over design. Subjects received single or multiple dose (an 8 day period) administration of oralABT-627 or matched placebo, in a dose range of 0.2,40 mg. The pharmacokinetics of ABT-627 were described and its effects on systemic haemodynamics under resting conditions and on forearm vasoconstriction in response to ET-1 were assessed. Results, ABT-627 was generally well tolerated in both studies, with transient headache being the most reported adverse event (in 62%vs 4% during placebo, P < 0.05, for Study 1 and in 42%vs 60%, P = 0.2, for Study 2). ABT-627 was rapidly absorbed, reaching maximum plasma levels at ,,1 h post dose. Single dose ABT-627, at a dose of 20 and 40 mg, inhibited ET-1 induced forearm vasoconstriction at 8 h post dose. Eight days ABT-627 treatment, at a dose level of 5 mg and above, also effectively blocked forearm vasoconstriction to ET-1. ABT-627 caused a significant reduction in peripheral resistance as compared with placebo (16 ± 1 vs 19 ± 1, 18 ± 2 vs 23 ± 3, 15 ± 1 vs 17 ± 1 AU at 1, 5, 20 mg in Study 2) with only a mild decrease in blood pressure (79 ± 2 vs 84 ± 3, 80 ± 4 vs 90 ± 5, 75 ± 3 vs 79 ± 1 at 1, 5, 20 mg in Study 2). ABT-627 caused a moderate dose-dependent increase in circulating immunoreactive ET levels (a maximal increase of 50% over baseline at the 20 mg dose level). Conclusions, The oral ETA receptor blocker ABT-627 is well tolerated, rapidly absorbed, effectively blocks ET-1 induced vasoconstriction and causes a decrease in total peripheral resistance and mean arterial pressure. Our data suggest that ABT-627 may be a valuable tool in treatment of cardiovascular disease. [source] Developmental disorders of glucose metabolism in infantsCHILD: CARE, HEALTH AND DEVELOPMENT, Issue 2002R. Hume Abstract Background Developmental failures to adequately control postnatal blood glucose levels are common in the transition from fetal to infant life and can persist for many months. The standard method of functionally measuring hepatic glucose production and/or disordered glucose production is the response to a glucagon tolerance test. Method We adapted the standard glucagon tolerance test used for children and adults for use in preterm infants. 79 consecutive preterm infants gestational age range 25,36 weeks (mean 32.2 weeks), mean birth weight 1.66 kg admitted to the Neonatal Intensive Care Unit, Ninewells Hospital, Dundee and who survived to discharge home were recruited into the study. At the time of discharge home the characteristics of the group were as follows: adjusted mean gestational age 36.7 weeks, mean discharge weight 2.23 kg. Results In this study of preterm infants the maximal increase in plasma glucose following administration of a glucagon tolerance test is 1.39 ± 07 mmol/L, n = 78 (range 0,3.98 mmol/L). Conclusions An increase in plasma glucose of less than 4 mmol/L is considered abnormal in adults following administration of a fasting glucagon tolerance test. The responses of preterm infants and adults to glucagon are clearly different. The attenuated response to glucagon in the preterm infants is consistent with the low levels of hepatic glucose-6-phosphatase activity in premature infants as glucose-6-phosphatase is the terminal step of the two main pathways of liver glucose production. [source] Forced swim stress activates rat hippocampal serotonergic neurotransmission involving a corticotropin-releasing hormone receptor-dependent mechanismEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2002Astrid C. E. Linthorst Summary Serotonin is important for adequate coping with stress. Aberrant serotonin function is implicated in the aetiology of major depression and anxiety disorders. Dysregulation of the hypothalamic,pituitary,adrenocortical axis, involving elevated corticotropin-releasing hormone (CRH) activity, also plays a role in these stress-related illnesses. Here we studied the effects of stress on hippocampal serotonin and the role of the CRH system using in vivo microdialysis. First, rats were subjected to a forced swim stress, resulting in a dramatic increase in hippocampal serotonin (1500% of baseline), which was associated with the occurrence of diving behaviour. The diving-associated increase in serotonin depended on activation of CRH receptors, as it was antagonized by intracerebroventricular pretreatment with D -Phe-CRH12,41. Secondly, the effects of intracerebroventricular administration of CRH and urocortin (0.03,1.0 µg) were studied. Both CRH and urocortin caused a dose-dependent rise in hippocampal serotonin (maximally 350% of baseline) and 5-hydroxyindoleacetic acid levels, suggesting the involvement of CRH receptor type 1. Because the effects of urocortin were prolonged, CRH receptor type 2 could play a role in a later phase of the neurotransmitter response. Experiments using adrenalectomized rats showed that CRH-induced serotonin changes were adrenally independent. These data suggest that the raphe-hippocampal serotonin system is able to mount, CRH receptor-dependent, responses to specific stressful situations that surpass the usually observed maximal increases of about 300% of baseline during stress and enhanced vigilance. [source] | |||||||||||||