Assay of growth hormone and gonadotrophins in relation to clinical problems

Since the early 1900's, many investigators have studied the effects of pituitary ablation and the mode of action of the hypophyseal hormones. Initially, work was mainly directed towards the purification and bioassay of the various hormones, although the effects of hormone administration were also studied. Recently, attempts have been made to synthesise some of the hormones. The aim of this thesis is to describe a series of studies undertaken in an attempt to develop new assay methods for growth hormone and the gonadotropins and the application of these procedures. (89) An investigation of the bioassay for growth hormone depending on the increase in tibial epiphyseal cartilage width in immature hypophysectomised rats has shown that the method is not specific and is of low sensitivity. The procedure has been used to compare the potency of pituitary extracts from different species and to provide a measure of the effect on body growth and on cartilage width of two synthetic compounds and of nerve section. A dithiocarbamoylhydrazine derivative, Compound 33» 828 (I.C.I.) was found to have a markedly inhibitory effect on general body growth and cartilage width, possibly due to the toxicity of the compound. A synthetic polypeptide, Ciba 50920-Ba which is claimed to have an adrenocorticotrophic hormone-like action on the adrenal, had no marked effect on cartilage growth. It has also been shown that the artificial induction of muscular atrophy in young rats by section of the sciatic nerve did not interfere with cartilage growth and that the administration of pituitary hormones to animals treated in this way was without effect. (166) A haemagglutination-inhibition method has been developed for the assay of growth hormone and has proved to be sensitive and highly specific. When estimates of the growth hormone potency of standard pituitary preparations were made by both the bioassay described above and the immunological method, similar results were obtained. The immunological procedure was, however, found not to be sufficiently sensitive for clinical application. A latex particle agglutination-inhibition method for the quantitative determination of human chorionic gonadotrophin has also been developed. This again proved to be unsuitable for clinical application. (88) The pyruvic acid oontent of the immature rat ovary, both prior to and following gonadotrophic stimulation, was estimated by two different methods. A marked rise in pyruvic acid was noted following initial stimulation with pregnant mare serum gonadotrophin, but this rapidly fell to a low level which could not be altered by further gonadotrophic stimulation. The relationship between pyruvic acid and gonadotrophic stimulation is discussed. (65) The studies reported in this thesis have shown that the methods available for the quantitative determination of growth hormone and gonadotrophins axe not entirely satisfactory because of poor sensitivity or lack of specificity. However, despite these limitations, useful information can be obtained by these procedures although it is clear that they are not suitable for clinical application. The development of more sensitive and specific methods for the estimation of these hormones is therefore necessary and it is suggested that future work in this field should be directed towards this end

4,4′-{[4-(2,2′:6′,2′′-Terpyridin-4′-yl)phen­yl]imino}­dibenzaldehyde

The central pyridine ring of the 2,2′:6′,2′′-terpyridine fragment of the title compound, C35H24N4O2, forms dihedral angles of 8.3 (2), 10.6 (3) and 39.4 (3)°, respectively, with the two outer pyridine rings and the attached benzene ring. In the crystal, weak C—H⋯O inter­actions link the mol­ecules into chains in [010]

Evolution of microflares associated with bright points in coronal holes and in quiet regions

We aim to find similarities and differences between microflares at coronal bright points found in quiet regions and coronal holes, and to study their relationship with large scale flares. Coronal bright points in quiet regions and in coronal holes were observed with Hinode/EIS using the same sequence. Microflares associated with bright points are identified from the X-ray lightcurve. The temporal variation of physical properties was traced in the course of microflares. The lightcurves of microflares indicated an impulsive peak at hot emission followed by an enhancement at cool emission, which is compatible with the cooling model of flare loops. The density was found to increase at the rise of the impulsive peak, supporting chromospheric evaporation models. A notable difference is found in the surroundings of microflares; diffuse coronal jets are produced above microflares in coronal holes while coronal dimmings are formed in quiet regions. The microflares associated with bright points share common characteristics to active region flares. The difference in the surroundings of microflares are caused by open and closed configurations of the pre-existing magnetic field.Comment: 9 pages, 11 figures, accepted for publication in A&

The gamma-ray giant flare from SGR1806-20: Evidence for crustal cracking via initial timescales

We report here on serendipitous observations of the intense gamma-ray flare from SGR 1806-20 that occured on 27 December 2004. Unique data from the Cluster and Double Star-2 satellites, designed to study the Earth's magnetosphere, provide the first observational evidence of three separate timescales within the early (first 100ms) phases of this class of events. These observations reveal that, in addition to the initial very steep (<0.25ms) X-ray onset, there is firstly a 4.9ms exponential rise timescale followed by a continued exponential rise in intensity on a timescale of 70ms. These three timescales are a prominent feature of current theoretical models including the timescale (several ms) for fracture propagation in the crust of the neutron star.Comment: 10 pages including 2 figures Ap J Letters in press, May 200

Reconstructing the 3-D Trajectories of CMEs in the Inner Heliosphere

A method for the full three-dimensional (3-D) reconstruction of the trajectories of coronal mass ejections (CMEs) using Solar TErrestrial RElations Observatory (STEREO) data is presented. Four CMEs that were simultaneously observed by the inner and outer coronagraphs (COR1 and 2) of the Ahead and Behind STEREO satellites were analysed. These observations were used to derive CME trajectories in 3-D out to ~15Rsun. The reconstructions using COR1/2 data support a radial propagation model. Assuming pseudo-radial propagation at large distances from the Sun (15-240Rsun), the CME positions were extrapolated into the Heliospheric Imager (HI) field-of-view. We estimated the CME velocities in the different fields-of-view. It was found that CMEs slower than the solar wind were accelerated, while CMEs faster than the solar wind were decelerated, with both tending to the solar wind velocity.Comment: 17 pages, 10 figures, 1 appendi

Disorder-to-order transition in the magnetic and electronic properties of URh_2Ge_2

We present a study of annealing effects on the physical properties of tetragonal single--crystalline URh_2Ge_2. This system, which in as-grown form was recently established as the first metallic 3D random-bond heavy-fermion spin glass, is transformed by an annealing treatment into a long-range antiferromagnetically (AFM) ordered heavy-fermion compound. The transport properties, which in the as-grown material were dominated by the structural disorder, exhibit in the annealed material signs of typical metallic behavior along the crystallographic a axis. From our study URh_2Ge_2 emerges as exemplary material highlighting the role and relevance of structural disorder for the properties of strongly correlated electron systems. We discuss the link between the magnetic and electronic behavior and how they are affected by the structural disorder.Comment: Phys. Rev. B, in print (scheduled 1 Mar 2000

What is the Nature of EUV Waves? First STEREO 3D Observations and Comparison with Theoretical Models

One of the major discoveries of the Extreme ultraviolet Imaging Telescope (EIT) on SOHO were intensity enhancements propagating over a large fraction of the solar surface. The physical origin(s) of the so-called `EIT' waves is still strongly debated. They are considered to be either wave (primarily fast-mode MHD waves) or non-wave (pseudo-wave) interpretations. The difficulty in understanding the nature of EUV waves lies with the limitations of the EIT observations which have been used almost exclusively for their study. Their limitations are largely overcome by the SECCHI/EUVI observations on-board the STEREO mission. The EUVI telescopes provide high cadence, simultaneous multi-temperature coverage, and two well-separated viewpoints. We present here the first detailed analysis of an EUV wave observed by the EUVI disk imagers on December 07, 2007 when the STEREO spacecraft separation was $\approx 45^\circ$. Both a small flare and a CME were associated with the wave cadence, and single temperature and viewpoint coverage. These limitations are largely overcome by the SECCHI/EUVI observations on-board the STEREO mission. The EUVI telescopes provide high cadence, simultaneous multi-temperature coverage, and two well-separated viewpoints. Our findings give significant support for a fast-mode interpretation of EUV waves and indicate that they are probably triggered by the rapid expansion of the loops associated with the CME.Comment: Solar Physics, 2009, Special STEREO Issue, in pres

Gamma-Ray Bursts: The Underlying Model

A pedagogical derivation is presented of the ``fireball'' model of gamma-ray bursts, according to which the observable effects are due to the dissipation of the kinetic energy of a relativistically expanding wind, a ``fireball.'' The main open questions are emphasized, and key afterglow observations, that provide support for this model, are briefly discussed. The relativistic outflow is, most likely, driven by the accretion of a fraction of a solar mass onto a newly born (few) solar mass black hole. The observed radiation is produced once the plasma has expanded to a scale much larger than that of the underlying ``engine,'' and is therefore largely independent of the details of the progenitor, whose gravitational collapse leads to fireball formation. Several progenitor scenarios, and the prospects for discrimination among them using future observations, are discussed. The production in gamma- ray burst fireballs of high energy protons and neutrinos, and the implications of burst neutrino detection by kilometer-scale telescopes under construction, are briefly discussed.Comment: In "Supernovae and Gamma Ray Bursters", ed. K. W. Weiler, Lecture Notes in Physics, Springer-Verlag (in press); 26 pages, 2 figure