Search results for "Pressure"
showing 10 items of 4493 documents
Data from: An aposematic colour-polymorphic moth seen through the eyes of conspecifics and predators - sensitivity and colour discrimination in a tig…
2019
1. Although predation is commonly thought to exert the strongest selective pressure on colouration in aposematic species, sexual selection may also influence colouration. Specifically, polymorphism in aposematic species cannot be explained by natural selection alone. 2. Males of the aposematic wood tiger moth (Arctia plantaginis) are polymorphic for hindwing colouration throughout most of their range. In Scandinavia, they display either white or yellow hindwings. Female hindwing colouration varies continuously from bright orange to red. Redder females and yellow males suffer least from bird predation. 3. White males often have higher mating success than yellow males. Therefore, we ask wheth…
Mechanisms of Cell-Volume Regulation in the Central Nervous System
2017
Function and viability of every cell is dependent on the proper control of its shape and volume. In the brain, which is protected by a rigid outer shell, cell-volume regulation is of particular importance, since large volume changes affect cerebral perfusion and, hence, function. Neuronal activation leads to constant changes of the ionic and metabolic composition of the brain’s extracellular space. These changes are buffered by astrocytes on the expense of constant changes in cell volume. Under pathological conditions, the ability of astrocytes to maintain the homeostasis of the brain is overwhelmed and permanent cell swelling, cytotoxic edema, occurs. The current chapter describes the prin…
Functional Morphology of Human Arteries During Fetal and Postnatal Development
1980
The equilibrium between the distending force of the blood pressure and the arterial wall is determined essentially by a simple law of mechanics, the law of Laplace. According to this law, the total force or tension (T) in the vessel’s wall represents the product of the radius of the vessel (r) and the blood pressure (p), T = r.p. The law of Laplace may be used to estimate and compare the tension produced by blood pressure in vessels of different size and thereby determine the increase in functional load on arteries. Since tension increases not only with blood pressure but also with the radius of the vessel, the highest tension is presumably produced in the wall of the ascending aorta where …
Determination of the Optimal Saddle Height for Leisure Cycling (P188)
2008
Several studies have been done on road racing cycling and triathlon to determine the optimal saddle height (LINF) in terms of efficiency. However, cycling is becoming nowadays not only a popular sport but also a mass mean of transport were comfort takes priority over efficiency. The aim of this study is to determine an optimal saddle height (LINF) to improve comfort in leisure cycling. Five male subjects (height mean=172.2 cm, std=1.34 cm; crotch height mean=81.25cm, std=0.88cm) tested 9 prototypes of the company ORBEA with 3 levels of LINF. The test consisted in one hour cycling in lab conditions and four different techniques were used to evaluate the LINF: 3-D movement analysis was used t…
19F-MRI of perflubron for measurement of oxygen partial pressure in porcine lungs during partial liquid ventilation
2001
A method for in vivo measurement of oxygen partial pressure (pO2) in porcine lungs during partial liquid ventilation (PLV) with perflubron (PFOB) was developed. A pulse sequence for high-resolution MRI of the distribution of PFOB in the lung after intratracheal administration was developed as well. Moreover, quantitative measurements of longitudinal relaxation time T(1) of (19)F resonances for assessment of regional pO2 are described. Due to the need to acquire data during a single expiratory breathhold, only low SNRs were achieved in vivo. Therefore, simulations were performed to investigate the influence of background noise on T(1) values calculated from data with low SNR. Based on these …
Changes of plasma endothelin and growth factor levels, and of left ventricular mass, after chronic AT1-receptor blockade in human hypertension.
1998
The stimulation of autocrine and paracrine factors such as basic fibroblast- (bFGF) and platelet-derived (PDGF) growth factors mediates many of the growth-promoting actions of angiotensin II. The aim of this study was to evaluate the effect of chronic AT1-receptor blockade on plasma endothelin-1 (ET-1) and growth factors levels, and on left ventricular mass, in essential hypertension (EH). The study population consisted of 16 patients with mild-moderate EH, and 25 normotensive controls. In the EH patients under basal conditions, and after 3 and 6 months of chronic therapy with Losartan 50 mg/day, we measured serum levels of ET-1, bFGF and PDGF, and tumor necrosis factor (TNF). At the same t…
Comparison of frequency domain measures based on spectral decomposition for spontaneous baroreflex sensitivity assessment after Acute Myocardial Infa…
2021
Abstract The objective of this study is to present a new method to assess in the frequency domain the directed interactions between the spontaneous variability of systolic arterial pressure (SAP) and heart period (HP) from their linear model representation, and to apply it for studying the baroreflex control of arterial pressure in healthy physiological states and after acute myocardial infarction (AMI). The method is based on pole decomposition of the model transfer function and on the following evaluation of causal measures of coupling and gain from the poles associated to low frequency (0.04−0.15 Hz) oscillatory components. It is compared with traditional non-causal approaches for the sp…
Cardiovascular risk in psoriatic arthritis, a narrative review
2020
Abstract Introduction Psoriatic arthritis (PsA) is a chronic inflammatory rheumatism characterized for a long time by a high degree of cardiovascular risk. Chronic inflammation is one of the mechanisms that explain this cardiovascular excess of risk through direct and indirect pathways. In recent years, epidemiological data have changed somewhat since the increasing use of bio-drugs that are effective in reducing this inflammation. The purpose of this review is to assess the current state of cardiovascular morbidity and mortality in PsA and thus to assess the cardiovascular risk in case of PsA. Method We conducted a literature review using Pubmed and Medline databases with the following key…
Does the renin-angiotensin system also regulate intra-ocular pressure?
2009
The renin-angiotensin-aldosterone system is known to play an essential role in controlling sodium balance and body fluid volumes, and thus blood pressure. In addition to the circulating system which regulates urgent cardiovascular responses, a tissue-localized renin-angiotensin system (RAS) regulates long-term changes in various organs. Many recognized RAS components have also been identified in the human eye. The highly vasoconstrictive angiotensin II (Ang II) is considered the key peptide in the circulatory RAS. However, the ultimate effect of RAS activation at tissue level is more complex, being based not only on the biological activity of Ang II but also on the activities of other produ…
Effectiveness and quality of life 10 years after transobturator suburethral tape surgery for stress urinary incontinence
2018
AIM We aimed to measure the effectiveness and quality of life (QoL) 10 years after transobturator suburethral tape surgery. METHODS We carried out a prospective observational study of 42 women assessed 10 years after surgical intervention with the transobturator technique. The main outcome measures were subjective and objective cure or improvement, complications, and changes in QoL. RESULTS The median abdominal leak point pressure had been 92 (82-113) mL H2 O prior to surgery. Thirty-six women (85.7%) remained cured (negative cough test) and 13 (31%) reported urine leakage during physical activity, percentages which were similar to those at a previous assessment at the 5th year. Urgency uri…