87,630 research outputs found
Hybrid Design of the BaBar silicon vertex tracker
No full textIn this paper we describe the design of the readout hybrid of the BABAR Silicon Vertex Tracker (SVT)
Tracer diffusion in F-actin and Ficoll mixtures. Toward a model for cytoplasm
No full textWe have previously reported that self-diffusion of inert tracer particles in the cytoplasm of living Swiss 3T3 cells is hindered in a size-dependent manner (Luby-Phelps, K., D.L. Taylor, and F. Lanni. 1986. J. Cell Biol. 102:2015–2022; Luby-Phelps, K., P.E. Castle, D.L. Taylor, and F. Lanni. 1987. Proc Natl. Acad. Sci. USA. 84:4910–4913). Lacking a theory that completely explains our data, we are attempting to understand the molecular architecture responsible for this phenomenon by studying tracer diffusion in simple, reconstituted model systems. This report contains our findings on tracer diffusion in concentrated solutions of Ficoll 70 or Ficoll 400, in solutions of entangled F-actin filaments, and in solutions of entangled F-actin containing a background of concentrated Ficoll particles or concentrated bovine serum albumin (BSA). A series of size-fractionated fluorescein-Ficolls were used as tracer particles. By fluorescence recovery after photobleaching (FRAP), we obtained the mean diffusion coefficients in a dilute, aqueous reference phase (Do), the mean diffusion coefficients in the model matrices (D), and the mean hydrodynamic radii (RH) for selected tracer fractions. For each model matrix, the results were compared with similar data obtained from living cells. As in concentrated solutions of globular proteins (Luby-Phelps et al., 1987), D/Do was not significantly size-dependent in concentrated solutions of Ficoll 400 or Ficoll 70. In contrast, D/Do decreased monotonically with increasing RH in solutions of F-actin ranging in concentration from 1 to 12 mg/ml. This size dependence was most pronounced at higher F-actin concentrations. However, the shape of the curve and the extrapolated value of D/Do in the limit, RH----O did not closely resemble the cellular data for tracers in the same size range (3 less than RH less than 30 nm). In mixtures of F-actin and Ficoll or F-actin and BSA, D/Do was well approximated by D/Do for the same concentration of F-actin alone multiplied by D/Do for the same concentrations of Ficoll or BSA alone. Based on these results, it is possible to model the submicroscopic architecture of cytoplasm in living cells as a densely entangled filament network (perhaps made up of F-actin and other filamentous structures) interpenetrated by a fluid phase crowded with globular macromolecules, which in cytoplasm would be primarily proteins
Effect of 3,3\m='\-di-iodothyronineand 3,5-di-iodothyronine on rat liver mitochondria
No full text(Requests for offprints should be addressed to F. Goglia
La valutazione della negligenza del debitore nel nuovo codice civile e commerciale argentino
No full textIl cultore del diritto è posto difronte all’operatività di alcune macro-regole che emergono in via ricostruttiva dall’analisi del nuovo codice argentino. L’indagine muove dalla negligenza vs. la responsabilità, prendendo in considerazione l’ideale di comportamento corretto ed onesto che si concretizza tramite il rinvio alla buona fede e alla diligenza
El consumidor latinoamericano : nuevos desafíos para la harmonización del derecho
No full textEl artículo tiene por objetivo comparar las definiciones legales de consumidor de algunos países latinoamericanos y textos supranacionales de la región, mostrando sus similitudes para comenzar a sentar las bases del proceso de armonización del derecho del consumidor en América Latina. En esta perspectiva, la atención del comparatista debe estar dirigida no solo a los textos normativos sino también a las tendencias del mercado: en el ensayo se subraya cómo hace hincapié un nuevo modelo de consumo, el de economías colaborativas, innovador desde el punto de vista del derecho privado y de los tipos contractuales y por eso estrechamente relacionado con el proceso de armonización antes mencionado
THYROID HORMONE AND UNCOUPLING PROTEINS.
No full textThyroid hormone (TH/T3) exerts many of its effects on energy metabolism by affecting gene transcription. However, although this is an important target for T3, only a limited number of T3-responsive genes have been identified and studied. Among these, the genes for uncoupling proteins (UCPs) have attracted the interest of scientists. Although the role of UCP1 seems quite well established, uncertainty surrounds the physiological function of the recently discovered UCP1 analogs, UCP2 and UCP3. The literature suggests that T3 affects both the expression and the activity of each of these UCPs but further studies are needed to establish whether the mechanisms activated by the hormone are the same. Recently, because of their larger range of expression, much attention has been devoted to UCP2 and UCP3. Most detailed studies on the involvement of these proteins as mediators of the effects of T3 on metabolism have focused on UCP3 because of its expression in skeletal muscle. T3 seems to be unique in having the ability to stimulate the expression and activity of UCP3 and this may be related to the capacity of T3 to activate the integrated biochemical processes linked to UCP activity, such as those related to fatty acids, coenzyme Q and free radicals. © 2003 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved
How the thyroid controls metabolism in the rat: different roles for triiodothyronine and diiodothyronines.
No full textAlthough the first evidence of a relationship between the thyroid and metabolism was reported in 1895, the mechanism by which thyroid hormones influence resting metabolic rate in whole animals is still poorly understood. This paper reports an attempt to test whether diiodothyronines (T2s) and triiodothyronine (T3) have different roles in the control of resting metabolism (RM). Changes in resting metabolic rate were measured in hypothyroid rats treated acutely (25 μg (100 g body weight)-1) either with one of the T2s or with T3. Injection of T3 induced an increase of about 35% in RM that started 25-30 h after the injection and lasted until 5-6 days after the injection, the maximal value being observed at 50-75 h. The injection of T2s evoked a temporally different pattern of response. The increases in RM started 6-12 h after the injection, had almost disappeared after 48 h, and the maximal stimulation was observed at 28-30 h. When actinomycin D (an inhibitor of protein synthesis) and T3 were given together, the stimulation of RM was almost completely abolished. The simultaneous injection of actinomycin D and either of the T2s, on the other hand, did not cause any attenuation of the stimulation seen with the T2s alone. Following chronic treatment (3 weeks) with either T3 or T2s there was a stimulation of growth only after the administration of T3. Chronic administration of either T2s or T3 to hypothyroid rats significantly enhanced the oxidative capacity of each of the tissues considered. In the case of T2s the stimulation was almost the same whether it was expressed as an increase in specific activity or total tissue activity. In the case of T3 the increases were, in the main, secondary to the hypertrophic or hyperplastic effect. These results indicate that T2s and T3 exert different effects on RM. The effects of T2s are rapid and possibly mediated by their direct interaction with mitochondria. Those of T3 are slower and more prolonged, and at least partly attributable to a modulation of the cellularity of tissues that are metabolically very active
Thyroid hormones, mitochondrial bioenergetics and lipid handling
No full textPurpose of Review: The article is principally intended to describe the recent evolutions in the field of research concerned with the metabolic actions of thyroid hormones and those of some of their metabolites or derivatives. Mitochondria, as a result of their functions, represent the principal objective of scientists investigating the mechanisms underlying the effects of thyroid hormones or their metabolites/derivatives. Recent Findings: Indeed, some important recent findings concern these organelles, and in particular mitochondrial uncoupling and its modulation by effectors. Traditionally, thyroxine (T4) and tri-iodo-L-thyronine (T3) were the only thyroid hormones considered to have metabolic effects, and they alone were considered for potential as agents that might counteract some important abnormalities such as dyslipidaemias and obesity. Several observations, however, led to a reconsideration of this idea. In recent years, studies dealing with the biological activities of some natural metabolites or structural analogues of thyroid hormones have revealed abilities to ameliorate some major worldwide medical problems, such as artherosclerosis, obesity and cardiovascular diseases. Among natural metabolites, 3,5-diiodothyronine (T2) has been shown to powerfully reduce adiposity and dyslipidaemia and to reverse hepatic steatosis without unfavourable side-effects usually observed when T3 or T4 is used. Examples of synthetic analogues are GC-1 (or sobetirome) and KB2115 (or eprotirome) which show ipolipidaemic and antiaterogenic capacities. Clinical trials are in progress for these last agents. Summary: In view of the above-mentioned actions, some of these compounds are now undergoing clinical trials and may have important implications for clinical practice or researches in the field of both endocrinology and metabolic-related abnormalities such as diabetes and dyslipidaemias. © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
OXIDATIVE CAPACITY, RESPIRATORY VARIABLES AND ALPHA-GLYCEROPHOSPHATE DEHYDROGENASE-ACTIVITY IN DIFFERENT MITOCHONDRIAL SUBPOPULATIONS
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