Growth hormone and aging

Les alteracions vasculars i degeneratives del sistema nerviós central (SNC) són dues de les causes més comunes de malaltia i de mort entre la gent gran; ambdues es correlacionen amb l'edat, amb la deficiència en GH, i poden afectar les funcions fisiològiques de la població d'edat avançada. Amb la finalitat de clarificar els efectes de la GH en el metabolisme, en els vasos i en el SNC, hem dut a terme un estudi in vivo utilitzant rates vellesWistar tractades crònicament amb GH. Les rates velles varen presentar un augment en el pes de greix i una disminució de l'índex específic de gravetat (SGI) (p < 0,05) en comparar-les amb les rates adultes no tractades. La GH va reduir el pes en greix (p < 0,05), i va mostrar també una tendència a augmentar l'SGI. Es va analitzar també la resposta de diverses substàncies vasoactives en els anells aòrtics, i es va demostrar una disminució de la vasodilatació per acetilcolina i isoprenalina (p < 0,05) en els animals vells. La contracció induïda per acetilcolina+L-NAME era més alta en els animals vells que en els adults. L'administració de GH millorava les respostes vasodilatadores (p < 0,05) mentre que tendia a reduïr les respostes vasoconstrictores. L'àrea aòrtica mitja augmentava també en les rates velles, mentre que la GH reduïa aquest paràmetre (p < 0,05). Les poblacions neuronals es reduïen en els hipocamps de les rates velles en comparar-les amb les joves. Aquesta reducció estava asociada a un augment dels nucleosomes i a una reducció de Bcl2 en el cervell. Les caspases 3 i 9 també varen augmentar. El tractament amb GH va augmentar significativament el nombre de neurones i va reduir els nucleosomes i les caspases i augmentar el Bcl2. En conclusió, el tractament perGHindueix l'aparició d'efectes beneficiosos en la composició del cos i ha restablert també les funcions cerebrals i vasculars en les rates velles.Vascular and degenerative alterations of the central nervous system (CNS) are two of the most common reasons for illness and death in elderly people; they exhibit an age-related GH deficiency that can affect their physiological functions. A study was conducted under chronic in vivo conditions using old Wistar rats, in order to clarify the effects of GH on the metabolism, vessels, and the CNS. The old rats showed an increased fat weight and a decreased Specific Gravity Index (SGI) (p < 0.05), as compared to the adult animals. GH reduced the fat weight (p < 0.05) and tended to increase the SGI (N.S.). The response to several vasoactive substances in aortic rings showed impaired vasodilatation to Acetylcholine and Isoprenaline (p < 0.05) in the old animals. Contraction, induced by Acetylcholine+ L-NAME, was higher in the old rats than in the adults. GH administration improved the vasodilatory responses (p < 0.05) and tended to reduce the constrictory responses. The aortic media area was increased in the old rats, and GH reduced this parameter (p < 0.05). The neuronal populations were reduced in the hippocampi of the old rats as compared to the young ones. This reduction was associated with an increase in nucleosomes and a reduction in Bcl2 in the brain. An increase was also detected in caspases 3 and 9. GH treatment was able to significantly enhance the number of neurons by reducing the nucleosomes and the caspases and by increasing Bcl2. In conclusion,GHtreatment was able to show beneficial effects on body composition and was able to restore both vascular and brain functions in the old rats

Hamiltonian Poincar\'e Gauge Theory of Gravitation

We develop a Hamiltonian formalism suitable to be applied to gauge theories in the presence of Gravitation, and to Gravity itself when considered as a gauge theory. It is based on a nonlinear realization of the Poincar\'e group, taken as the local spacetime group of the gravitational gauge theory, with $SO(3)$ as the classification subgroup. The Wigner--like rotation induced by the nonlinear approach singularizes out the role of time and allows to deal with ordinary $SO(3)$ vectors. We apply the general results to the Einstein--Cartan action. We study the constraints and we obtain Einstein's classical equations in the extremely simple form of time evolution equations of the coframe. As a consequence of our approach, we identify the gauge--theoretical origin of the Ashtekar variables.Comment: 38 pages, plainTe

Non-Riemannian Gravity and the Einstein-Proca System

We argue that all Einstein-Maxwell or Einstein-Proca solutions to general relativity may be used to construct a large class of solutions (involving torsion and non-metricity) to theories of non-Riemannian gravitation that have been recently discussed in the literature.Comment: 9 pages Plain Tex (No Figures), Letter to Editor Classical and Quantum Gravit

Towards complete integrability of two dimensional Poincar\'e gauge gravity

It is shown that gravity on the line can be described by the two dimensional (2D) Hilbert-Einstein Lagrangian supplemented by a kinetic term for the coframe and a translational {\it boundary} term. The resulting model is equivalent to a Yang-Mills theory of local {\it translations} and frozen Lorentz gauge degrees. We will show that this restricted Poincar\'e gauge model in 2 dimensions is completely integrable. {\it Exact} wave, charged black hole, and `dilaton' solutions are then readily found. In vacuum, the integrability of the {\it general} 2D Poincar\'e gauge theory is formally proved along the same line of reasoning.Comment: 35 pages, report Cologne-thp-1993-H

Dark Matter Gravitational Interactions

We argue that the conjectured dark mater in the Universe may be endowed with a new kind of gravitational charge that couples to a short range gravitational interaction mediated by a massive vector field. A model is constructed that assimilates this concept into ideas of current inflationary cosmology. The model is also consistent with the observed behaviour of galactic rotation curves according to Newtonian dynamics. The essential idea is that stars composed of ordinary (as opposed to dark matter) experience Newtonian forces due to the presence of an all pervading background of massive gravitationally charged cold dark matter. The novel gravitational interactions are predicted to have a significant influence on pre-inflationary cosmology. The precise details depend on the nature of a gravitational Proca interaction and the description of matter. A gravitational Proca field configuration that gives rise to attractive forces between dark matter charges of like polarity exhibits homogeneous isotropic eternal cosmologies that are free of cosmological curvature singularities thus eliminating the horizon problem associated with the standard big-bang scenario. Such solutions do however admit dense hot pre-inflationary epochs each with a characteristic scale factor that may be correlated with the dark matter density in the current era of expansion. The model is based on a theory in which a modification of Einsteinian gravity at very short distances can be expressed in terms of the gradient of the Einstein metric and the torsion of a non-Riemannian connection on the bundle of linear frames over spacetime. Indeed we demonstrate that the genesis of the model resides in a remarkable simplification that occurs when one analyses the variational equations associated with a broad class of non-Riemannian actions.Comment: 40 pages, 4 Postscript figure

An assessment of Evans' unified field theory I

Evans developed a classical unified field theory of gravitation and electromagnetism on the background of a spacetime obeying a Riemann-Cartan geometry. This geometry can be characterized by an orthonormal coframe theta and a (metric compatible) Lorentz connection Gamma. These two potentials yield the field strengths torsion T and curvature R. Evans tried to infuse electromagnetic properties into this geometrical framework by putting the coframe theta to be proportional to four extended electromagnetic potentials A; these are assumed to encompass the conventional Maxwellian potential in a suitable limit. The viable Einstein-Cartan(-Sciama-Kibble) theory of gravity was adopted by Evans to describe the gravitational sector of his theory. Including also the results of an accompanying paper by Obukhov and the author, we show that Evans' ansatz for electromagnetism is untenable beyond repair both from a geometrical as well as from a physical point of view. As a consequence, his unified theory is obsolete.Comment: 39 pages of latex, modified because of referee report, mistakes and typos removed, partly reformulated, taken care of M.W.Evans' rebutta

Deriving the mass of particles from Extended Theories of Gravity in LHC era

We derive a geometrical approach to produce the mass of particles that could be suitably tested at LHC. Starting from a 5D unification scheme, we show that all the known interactions could be suitably deduced as an induced symmetry breaking of the non-unitary GL(4)-group of diffeomorphisms. The deformations inducing such a breaking act as vector bosons that, depending on the gravitational mass states, can assume the role of interaction bosons like gluons, electroweak bosons or photon. The further gravitational degrees of freedom, emerging from the reduction mechanism in 4D, eliminate the hierarchy problem since generate a cut-off comparable with electroweak one at TeV scales. In this "economic" scheme, gravity should induce the other interactions in a non-perturbative way.Comment: 30 pages, 1 figur

de Sitter gauge theories and induced gravities

Pure de Sitter, anti de Sitter, and orthogonal gauge theories in four-dimensional Euclidean spacetime are studied. It is shown that, if the theory is asymptotically free and a dynamical mass is generated, then an effective geometry may be induced and a gravity theory emerges. The asymptotic freedom and the running of the mass might account for an In\"on\"u-Wigner contraction which induces a breaking of the gauge group to the Lorentz group, while the mass itself is responsible for the coset sector of the gauge field to be identified with the effective vierbein. Furthermore, the resulting local isometries are Lorentzian for the anti de Sitter group and Euclidean for the de Sitter and orthogonal groups.Comment: Sections added. Text reviewed. References added. 14 pages, no figures. Final version to appear in EPJ

Shells and humans: molluscs and other coastal resources from the earliest human occupations at the Mesolithic shell midden of El Mazo (Asturias, Northern Spain)

Human populations exploited coastal areas with intensity during the Mesolithic in Atlantic Europe, resulting in the accumulation of large shell middens. Northern Spain is one of the most prolific regions, and especially the so-called Asturian area. Large accumulations of shellfish led some scholars to propose the existence of intensification in the exploitation of coastal resources in the region during the Mesolithic. In this paper, shell remains (molluscs, crustaceans and echinoderms) from stratigraphic units 114 and 115 (dated to the early Mesolithic c. 9 kys cal BP) at El Mazo cave (Asturias, northern Spain) were studied in order to establish resource exploitation patterns and environmental conditions. Species representation showed that limpets, top shells and sea urchins were preferentially exploited. One-millimetre mesh screens were crucial in establishing an accurate minimum number of individuals for sea urchins and to determine their importance in exploitation patterns. Environmental conditions deduced from shell assemblages indicated that temperate conditions prevailed at the time of the occupation and the morphology of the coastline was similar to today (rocky exposed shores). Information recovered relating to species representation, collection areas and shell biometry reflected some evidence of intensification (reduced shell size, collection in lower areas of exposed shores, no size selection in some units and species) in the exploitation of coastal resources through time. However, the results suggested the existence of changes in collection strategies and resource management, and periods of intense shell collection may have alternated with times of shell stock recovery throughout the Mesolithic.This research was performed as part of the project “The human response to the global climatic change in a littoral zone: the case of the transition to the Holocene in the Cantabrian coast (10,000–5000 cal BC) (HAR2010-22115-C02-01)” funded by the Spanish Ministry of Economy and Competitiveness. AGE was funded by the University of Cantabria through a predoctoral grant and IGZ was funded by the Spanish Ministry of Economy and Competitiveness through a Juan de la Cierva grant. We also would like to thank the University of Cantabria and the IIIPC for providing support, David Cuenca-Solana, Alejandro García Moreno and Lucia Agudo Pérez for their help. We also thank Jennifer Jones for correcting the English. Comments from two anonymous reviewers helped to improve the paper

On Torsion-free Vacuum Solutions of the Model of de Sitter Gauge Theory of Gravity (II)

It is shown that all torsion-free vacuum solutions of the model of dS gauge theory of gravity are the vacuum solutions of Einstein field equations with the same positive cosmological constant. Furthermore, for the gravitational theories with more general quadratic gravitational Lagrangian ($F^2+T^2$), the torsion-free vacuum solutions are also the vacuum solutions of Einstein field equations.Comment: 4 pafes,0 figur