Search results for "STRAIN"
showing 10 items of 1955 documents
In vitro synthesis of dopamine and noradrenaline in the isolated rat pineal gland: day-night variations and effects of electrical stimulation.
1989
: Isolated rat pineal glands were incubated in vitro in a medium containing [I4C]dopamine or [14C]tyrosine, and the tissue contents of l4C-labelled and total dopamine and noradrenaline were determined by HPLC followed by electrochemical detection and scintillation spectrometry. During incubation with [l4C]dopamine, the labelled amine accumulated in pineal glands and was partially converted into [l4C]noradrenaline. Nomifensine, a neuronal amine uptake blocker, largely inhibited the accumulation of [l4C]dopamine and the formation of [14C]noradrenaline. These experiments demonstrated dopamine β-hydroxylase activity in the sympathetic nerves of the pineal gland. During incubation with [14C]tyro…
Depressive effect of LHRH on the numbers of "synaptic" ribbons and spherules in the pineal gland of diestrous rats.
1983
Previous studies have shown that LHRH or LHRH-like substances are present in the pineal gland. In order to investigate whether exogenous LHRH may affect the pineal gland, in the present study the effects of a single dose of LHRH (1 microgram, i.p.) on pineal "synaptic" ribbons and spherules as well as serum melatonin levels were examined in diestrous Wistar rats. One hour after the injection both ribbons and spherules exhibited a statistically significant decrease in number. Serum melatonin levels were not affected. It is concluded that humoral feedback mechanisms may exist between the hypothalamus and the pineal gland.
Circadian variations of ?synaptic? bodies in the pineal glands of Brattleboro rats
1990
The function of the mammalian pineal gland is regulated primarily by the sympathetic system. Arginine-vasopressin (AVP) may also be involved in the regulation of pineal melatonin synthesis under experimental conditions. The present study was conducted in the AVP-deficient rat strain, the Brattleboro rat, to investigate whether the numbers and rhythms of pineal "synaptic" bodies in this strain are different from those found in intact rats. AVP or its non-vasoconstrictive analog, deamino-D-AVP, was also injected intra-arterially in Brattleboro or Sprague-Dawley rats to test whether this procedure influences "synaptic" body numbers. Brattleboro rats were killed at different time-points through…
Increased LH and FSH release from the anterior pituitary of ovariectomized rat, in vivo, by copper-, nickel-, and zinc-LHRH complexes.
1992
Abstract The effect of Cu 2+ , Ni 2+ , Zn 2+ and their complexes with LHRH on the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH) was estimated in in vivo experiments with the use of the method proposed by Ramirez and McCann. Ovariectomized, estradiol, and progesterone pretreated rats were injected intraveneously either with LHRH alone, a metal ion alone, a mixture of metal and hormone, or a metal-LHRH complex. A metal alone or a mixture of it with LHRH did not affect gonadotropin release at all or no more than LHRH alone. However, the complex of Cu 2+ with LHRH brought about a high release of LH and even higher release of FSH. This indicates that copper complex i…
First-year engineering students’ use of their mathematics textbook - opportunities and constraints
2012
Published version of an article in the journal: Mathematics Education Research Journal. Also available from the publlisher at: http://dx.doi.org/10.1007/s13394-012-0040-9 The role of the mathematics textbook at tertiary level has received limited exposure in previous research although it is likely that students work individually and that some of this work depends on the use of the textbook. The aim of this study was to investigate the process of approaching the textbook from epistemological, cognitive, and didactical perspectives. The focus was on identifying and discussing the opportunities and constraints in the process. The study was an explorative case study and the participants were fi…
Educación artística : revista de investigación
2016
Resumen: El siguiente articulo pretende identificar posibles espacios comunes entre arte y educacion partiendo de la propuesta artistica Mapa dels Desitjos [1] del colectivo Crater [2] . Esta propuesta se llevo a cabo en el contexto de la XVII Mostra d’Art Public / Universitat Publica de la Universitat de Valencia. Mapa dels Desitjos surgio de la idea de preguntar a la comunidad universitaria como organizarian su vida si no tuviesen en cuenta la cuestion economica y de hacer publicas sus respuestas. A partir de esta experiencia, analizamos y reflexionamos en torno a cuatro preguntas que estructuran el analisis: ?Que paralelismos existen entre los roles de artista/publico y maestro/estudiant…
A PSO highway alignment optimization algorithm considering environmental constraints
2013
In recent years, there has been a growing need to develop and delineate algorithms that quickly provide optimized highway alignments. The matter is very complex since it is dominated by several factors and engineers have to achieve different and relevant targets (such as minimization of construction and earthwork costs, compliance with environmental and right-of-way constraints, maximization of safety and comfort for users, conformity with geometric standards). The possible solutions of this problem are clearly infinite and only modern artificial intelligence techniques can really simplify and speed up the highway design process. In this study a search algorithm, based on a Swarm Artificial…
Eettinen organisaatiokulttuuri : yhteydet työhyvinvointiin ja työpaikan vaihtoihin
2015
The research investigated the associations between ethical organizational cul ture, ethical strain (stress caused by ethical dilemmas) and job turnover. The first study investigated differences in employees’ ethical strain and their evalua tions of the ethical culture of their organizations between a public sector city organization (n = 3,123), an engineering firm (n = 287) and a bank (n = 187). In the second study, the connections between resources and personal authority for ethical actions (one dimension of the ethical culture of an organization) and eth ical strain in social affairs and health services in a public sector city organization were analyzed at the work-unit (n = 142) level as…
External sustainability in Spanish economy: bubbles and crises, 1970–2020
2023
We address the issue of the sustainability Spain’s exter-nal debt, using data for the period 1970–2020. To detect episodes of potentially explosive behavior of the Spanish net foreign assets over GDP ratio and the current account balance over GDP ratio, as well as episodes of external adjustments over this long period, we employ a recursive unit root test approach. Our empirical analysis leads us to conclude that there is some evidence of bubbles in the ratio between Spanish net foreign assets and the GDP. In contrast, the evidence that the ratio between the Spanish current account balance and the GDP had explosive subperiods is very weak. The episode of explosive behavior identified in the…
Stability of Embankments Resting on Foundation Soils with A Weak Layer
2021
The presence of weak layers in geotechnical systems, including soil or rock masses, both natural and man-made, is more frequent than is normally believed. Weak layers can affect both failure mechanisms, in drained and in undrained conditions, as well as in static and seismic conditions, and the safety factor. In the present study, conducted numerically using the finite-element method (FEM) Plaxis 2D code, the influence of a horizontal thin weak layer on stress and strain distribution, on failure mechanisms and on the overall stability of an embankment was evaluated. The results obtained prove that when the weak layer is located at a significant depth from the foundation plane, the failure m…