Biomedical subjects
Publications and source records attributed to A Chrysostomou.
Lymphocytic hypophysitis is a primary inflammatory disorder of the pituitary gland, which may cause panhypopituitarism. The majority of cases occur in women during the peripartum period and it is rare in men. We present a case, initially presenting with recurrent hypoglycaemic episodes, in a man with previously well-controlled type 2 diabetes mellitus.
Explore the source record for details and available documents.
Our discovery of high degrees of circular polarisation in some star-forming regions provides an attractive mechanism for the origin of homochirality. The largest degrees of circular polarisation, so far observed at near-infrared wavelengths, are thought to arise from the scattering of stellar radiation from aligned dust grains and are calculated to extend down to UV wavelengths. The extent of the region where circularly polarised light (CPL) of a single handedness originates is very large, and it is likely that the whole of a planetary system would see a single handedness of CPL also. We present the observational data, models of the scattering that leads to the production of CPL, and a model for the origin of homochirality. We also discuss briefly future laboratory and space-based experiments.
We report the detection of linear polarization from Sgr A* at 750, 850, 1350, and 2000 µm which confirms the contribution of synchrotron radiation. From the lack of polarization at longer wavelengths, it appears to arise in the millimeter/submillimeter excess. There are large position angle changes between the millimeter and submillimeter results, and these are discussed in terms of a polarized dust contribution in the submillimeter and various synchrotron models. In the model that best explains the data, the synchrotron radiation from the excess is self-absorbed in the millimeter region and becomes optically thin in the submillimeter. This implies that the excess arises in an extremely compact source of approximately 2 Schwarzschild radii.
Submillimeter polarimetric measurements of the 850 µm dust continuum emission associated with the class 0/I protostars in the Serpens dark cloud core are presented. The data are used to infer the magnetic field morphology in the region. Dust grain alignment in accretion flows and/or outflows is also briefly considered. The polarization vectors around the SMM-NW cluster of sources are more ordered than those observed near the SMM-SE cluster. Toward SMM-NW, the vectors are generally orientated north-south; between the intensity peaks in the SMM-SE region, the vectors are approximately east-west. In both regions, we suggest that the polarization pattern may be dictated by a large-scale magnetic field. We consider whether the rough northwest-southeast ridge of submillimeter sources was formed via cloud collapse along field lines that run perpendicular to this ridge. However, our data offer only very tentative support for this hypothesis. We further note that, although overall the polarization pattern in Serpens does not appear to be affected by the many outflows in the region, toward the most luminous source, SMM 1, the source of the Serpens radio jet, the vectors deviate considerably from the general pattern, instead being roughly perpendicular to the flow axis, as one would expect from a B-field oriented parallel with the flow.
Strong infrared circular polarization resulting from dust scattering in reflection nebulae in the Orion OMC-1 star-formation region has been observed. Circular polarization at shorter wavelengths might have been important in inducing chiral asymmetry in interstellar organic molecules that could be subsequently delivered to the early Earth by comets, interplanetary dust particles, or meteors. This could account for the excess of L-amino acids found in the Murchison meteorite and could explain the origin of the homochirality of biological molecules.
Strong infrared circular polarization resulting from dust scattering in reflection nebulae in the Orion OMC-1 star-formation region has been observed. Circular polarization at shorter wavelengths might have been important in inducing chiral asymmetry in interstellar organic molecules that could be subsequently delivered to the early Earth by comets, interplanetary dust particles, or meteors. This could account for the excess of L-amino acids found in the Murchison meteorite and could explain the origin of the homochirality of biological molecules.
Of 113 cyclosporine-treated primary renal allograft recipients, 60 were randomized to receive standard therapy without diltiazem (ND) and 53 received standard therapy plus diltiazem (D). There was no difference in CsA blood levels between ND and D at all intervals between 3 and 24 months follow-up, yet the D group required 35% less CsA than the ND group (measured at 12 months). At all intervals to 24 months there was no difference in blood pressure, renal function (as measured by serum creatinine), or in the number of grafts lost between the 2 groups (ND, 4 lost; D, 3 lost). There was no significant difference in the total number of rejection episodes in the 2 groups (ND, 89 episodes; D, 71 episodes). However, the severity of rejection episodes was greater in the ND group as evidenced by a significant difference in the usage of OKT3 (ND, 17 courses; D, 8 courses of OKT3, P < 0.05). Of the biopsy-proven episodes of rejection, there were more episodes of vascular rejection in the ND group (ND, 14 episodes; D, 3 episodes, P = 0.005). The incidence of primary nonfunction was less in the D group (ND, 16 patients; D, 5 patients, P = 0.05). It was concluded that the use of diltiazem was associated with a markedly reduced requirement for CsA without any adverse effect on graft function or graft outcome. Diltiazem with CsA was associated with fewer episodes of primary nonfunction and less-severe rejection episodes and in particular fewer episodes of vascular rejection.
Several theories of ageing predict that somatic mutations should increase with age. This prediction was tested for human lymphocytes using a recently developed clonal technique for enumeration of mutations, and an increase of 1.6% per year in mutations with age was detected.
Limiting-dilution cloning of human lymphocytes was used to study cloning and proliferation of lymphocytes in 10 young and 10 elderly individuals. The cloning efficiency for elderly individuals, 3.5%, was significantly lower than that for young individuals, 19.8%. Mixing experiments showed that this decrease was due to both a decrease in the frequency of the clone-forming cells and a decrease in the interacting ability of the lymphocytes. Lymphocytes from elderly individuals which did form clones, however, proliferated at the same rate as did those from young individuals.
Individuals occupationally exposed to cytotoxic drugs may be at risk owing to the effects of these agents on DNA. As an index of DNA damage, in vivo mutations were measured in lymphocytes from 24 oncology nurses or pharmacists and 24 matched controls. Mutation frequency was significantly increased in exposed individuals and appeared to be related to duration of exposure. However, the overall magnitude of the increase was small and its biological significance remains to be determined.