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Biomedical subjects

G H George

Publications and source records attributed to G H George.

6 recordsLinked to original sources
PubMed1999

Influence of current and past hormone replacement therapy on bone mineral density: a study of discordant postmenopausal twins.

There is controversy about the ideal timing of hormone replacement therapy (HRT) and duration of treatment. In this study we have examined intrapair differences in bone mineral density (BMD) in twins who were discordant for HRT use. Twin pairs in which only one co-twin had been exposed to HRT for more than 12 months continuously were selected from 365 postmenopausal monozygotic (MZ) and dizygotic (DZ) pairs recruited as part of the St Thomas' Adult UK Twin Registry of normal volunteers. BMD was measured by dual-energy X-ray absorptiometry at the lumbar spine and femoral neck. Intrapair differences in BMD between HRT users and non-users were compared. A total of 65 HRT-discordant pairs were identified, of which 36 were discordant for current HRT use (mean age: 55.3 years, median duration of HRT use: 36 months) and 29 were discordant for past HRT use (mean age: 60.4 years, median HRT duration: 30 months). Among current users BMD was consistently and significantly higher than in non-users at both sites (lumbar spine mean intrapair difference (IPD%): 12.3%, 95% confidence interval (CI): 7.1%, 17.5%; femoral neck IPD%: 8.6%, 95% CI: 3.4%, 13.7%). The intrapair differences were substantially smaller when past users and non-users were compared (lumbar spine IPD%: 2.4%, 95% CI: -3.7%, 8.6%; femoral neck IPD%: 0.4%, 95% CI: -5.3%, 6.0%). These differences remained little changed after adjusting for the potential confounding effects of the duration of HRT use, and intrapair differences in alcohol and tobacco consumption and physical exercise. The results confirm, in a closely matched design, the findings of other observational research that current use of HRT has a major effect on BMD at the lumbar spine and femoral neck. Past users of HRT do not, however, show the same benefits. The clinical implications of these findings are that HRT needs to be used continuously to influence BMD and that alternative treatments need to be considered in those who discontinue HRT.

Alcohol Drinking↗
PubMed1985

The onchocercal nodule: interrelationship of adult worms and blood vessels.

This study of onchocercal nodules reveals an intimate relationship between the cuticle of Onchocerca volvulus and the capillaries of the host. Perfusion of blood vessels with India ink and other special techniques reveal a proliferation of capillaries around the worms and communication between small vessels and the spaces around the worms. The space around the worm is continuous with the central fibrin lake. These findings, together with the fact that the worm's gut contains hemosiderin, suggest that the worm subverts the vascular reaction and causes within the nodule a controlled hemorrhage that serves the worm's nutritional needs. We believe this explains, in part, how worms survive in fibrous nodules for many years.

Animals↗
PubMedDate not supplied

Pathologic changes of human onchocerciasis: implications for future research.

Onchocerciasis--infection by Onchocerca volvulus--has four cardinal manifestations: dermatitis, subcutaneous nodules, sclerosing lymphadenitis, and eye disease. The first three are discussed here. The dermatitis begins when microfilariae degenerate in the dermis. This process is accompanied by inflammation, with degranulation of eosinophils and deposition of the major basic protein of the eosinophil granules on the cuticle of the microfilariae. So far as is known, the chronic effects of onchocerciasis are all a consequence of the degeneration of microfilariae. Subcutaneous nodules contain coiled adult worms and have an outer layer of fibrous scar and a central inflammatory cell exudate, which may cavitate. Perfusion of India ink reveals arborization of capillaries around adult worms, which derive nutrition from these networks. Onchocercal lymphadenitis is characterized initially by histiocytic hyperplasia and follicular atrophy and later by fibrosis and obstruction of lymph flow, a condition causing adenolymphocele ("hanging groin") and elephantiasis of the genitalia. Some patients appear to have immune tolerance to degenerating microfilariae, perhaps as a result of exposure in utero to microfilarial antigens in the maternal circulation. In contrast, other patients (Yemenites, for example) have a localized but intense response to a few microfilariae; these patients are hypersensitive--perhaps because they were not exposed to microfilarial antigens in utero. Autopsy data on infection of deep organs are limited.

Dermatitis↗