Biomedical subjects
Publications and source records attributed to Paul Chapman.
Stereotactic radiosurgery (SRS) is a technique for treating intracranial lesions with a high dose of ionizing radiation, usually in a single session, using a stereotactic apparatus for accurate localization and patient immobilization. This article describes several modalities of SRS and some of its applications, particularly for intracranial lesions.
The Iowa Gambling Task (IGT) is widely used to assess decision making under conditions of uncertainty in clinical as well as in nonclinical populations. However, there is still debate as to whether normal performance at this task relies on implicit, emotion-based processes that are independent of working memory. To clarify the role of working memory on normal performance on the IGT, participants performed the task under low or high working memory load. We used a modified version of the original task, in which the position of the four decks was randomized between trials. Results showed that only participants performing under low memory load significantly chose more advantageously halfway through the task. In addition, when comparing the number of cards chosen from the two decks with frequent losses, one advantageous and one disadvantageous, only participants performing under low memory load chose more cards from the advantageous deck. The present findings indicate that the processes underlying optimal advantageous performance on the IGT rely on working memory functions.
Diffuse melanosis is a rare event associated with advanced metastatic malignant melanoma. A 35-year-old woman with stage IV melanoma is presented, who developed slate bluish-gray to brown discoloration of her skin after chemotherapy-induced tumor lysis syndrome. A number of studies were performed to re-evaluate possible mechanisms of melanosis. Skin tissue was examined on routine hematoxylin-and-eosin-stained sections, Fontana stains, immunohistochemical studies with antibodies for Melan-A, gp100, tyrosinase, FXIIIa, and CD68, and by electron microscopy. The main cell types found to contain melanin pigment were histiocytes and dendritic cells. In the dermis, they were distributed mainly around venules. In the subcutaneous fat, they were scattered throughout the fat lobule. Melanin pigment was not only seen within cells but also extracellularly. No melanoma cells were seen in the skin. No increase in melanin pigment or number of melanocytes was seen in the epidermis. A bone marrow biopsy contained melanophages but no melanoma cells. Ultrastructural examination of the patient's serum revealed the presence of melanosomes. Sequence analysis of the tumor's cDNA failed to identify any mutations in the tyrosinase gene, and no tyrosinase protein was detected in non-melanocytic cells, indicating that it was unlikely that a mutation had resulted in a secretory form of the protein. These findings document that diffuse melanosis may result from tumor lysis, with release of melanosomes into the bloodstream.
A strategy for house fly (Musca domestica L.) control in intensive animal units in the United Kingdom was proposed by the Pesticide Safety Directorate (PSD) of the Ministry of Agriculture, Fisheries and Food in 1993. An advice leaflet was circulated to farmers, and label recommendations for insecticides used to control house flies were altered to prevent their long-term and frequent use. A study was carried out between 1996 and 1998 to gather data on insecticide use and resistance in house fly populations and compared with results from a study carried out in 1990-1992 to assess the impact of the 1993 label recommendations. As in the 1990-1992 study, resistance to methomyl, azamethiphos and pyrethrins + piperonyl butoxide was assessed. Larvicide tests with cyromazine, which had recently been released in the United Kingdom, were also included in this study. Most of the farmers claimed to have received and read the PSD insecticide advice leaflet, and half claimed to have altered insecticide treatments as a result. Comparing results for insecticides used before and after 1993, the proportion of farmers claiming to have used each of the insecticides had decreased. However, there had been no amelioration in resistance to synergised pyrethrins, and the number of house fly populations with reduced response to the insecticide baits had increased between 1990-1992 and 1996-1998. All the house fly populations tested were fully susceptible to cyromazine. There is an urgent need, therefore, to devise new strategies and particularly to minimize the risk of selecting for resistance to cyromazine.
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