Biomedical subjects
Publications and source records attributed to G A Pitson.
The clinical course of classical endemic Kaposi's sarcoma is indolent and bone involvement is rare unless via direct tumour extension. A case is presented in which isolated bone involvement occurred in the absence of significant overlying skin disease.
Antarctica is a unique and challenging environment where members of expeditions face a range of conditions not normally experienced. Ultraviolet (uv) radiation levels show marked variation during the year. The 25-hydroxy metabolite of vitamin D [25(OH)D] is largely produced by sunlight and shows a yearly variation in concentration that corresponds to uv radiation levels. The active metabolite 1,25-dihydroxyvitamin D [1,25(OH)2D] does not generally show any such variation provided 25(OH)D concentrations are sufficient. Previous studies have shown a seasonal variation in 25(OH)D with a significant winter drop. No other study of 1,25(OH)2D has been reported on members of Antarctic expeditions. A group of 19 men wintering at Davis Station (68 degrees 34' S) had four blood samples taken at 3-monthly intervals beginning in the Antarctic summer. Analysis for 25(OH)D showed a drop in concentration for each of the latter three sampling periods (P < 0.005). This correlated with uv radiation levels and would suggest that endogenous production of 25(OH)D ceases for at least the duration of the Antarctic winter. There were no significant alterations in 1,25(OH)2D or calcium concentrations over the same period. Providing that individuals with pre-existing vitamin D deficiencies are detected before departure for Antarctica and missions are limited in duration, clinical deficiency is unlikely to occur.
Immune function is modulated by a complex set of neuroendocrine factors including sex hormones, vitamin D metabolites and stress. Antarctic expeditioners exhibit reduced cell mediated immunity. Studies have also shown a reduction in testosterone levels in wintering expeditioners and suggested a correlation between levels of anxiety and reduced immune function in brief trip expeditioners. Nineteen male Antarctic expeditioners were followed by 3 monthly assessments of cell mediated immunity, levels of testosterone and vitamin D metabolite and psychological indicators of anxiety. There was a significant reduction in immune function during the study period, consistent with previous Antarctic studies. Levels of testosterone, anxiety and the immunoregulatory metabolite of vitamin D did not alter significantly. In this group the reduction in immune function did not show a correlation with levels of anxiety or the hormones studied.
Two primary sino-nasal melanomas are presented which were characterized by their botryoid growth pattern and myxoid stroma. These polypoid tumours contained small amounts of melanin and only focal areas of epithelioid cells. An in situ component was present in both of the tumours. Malignant melanoma should be considered when confronted by a myxoid tumour (with or without melanin) in the sino-nasal region. These tumours are widely infiltrative, and there is no evidence to suggest that they will behave any differently from conventional, non-botryoid, non-myxoid sino-nasal melanomas.
A 59 yr old male presented with abdominal pain and jaundice. CT scan showed a tumor in the pancreas with secondaries in the liver, peri-pancreatic lymph nodes, vertebral bone marrow and subcutaneous tissue of the neck together with a cervical lymph node. The patient died after 2 wks and autopsy revealed complete replacement of the pancreas by tumor. Careful dissection of both lungs failed to show any tumor. A diagnosis of primary small cell carcinoma of the pancreas was made. Review of the literature indicates that this type of carcinoma accounts for about 1% of all pancreatic cancers and is commoner in elderly males who have a history of cigarette smoking. There is usually a rapid progression of disease and widespread dissemination, especially if untreated. Some success has been obtained with chemotherapy.
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An enzyme immunoassay for serotyping human rotaviruses in stools and in cell culture was developed. Hyperimmune rabbit antisera to rotaviruses were used as capture antibodies, and rotavirus-neutralizing mouse monoclonal antibodies specific for serotypes 1, 2, 3, and 4 were used as detection reagents. Partial purification of monoclonal antibodies and inclusion of skim milk powder in antibody diluents contributed to assay specificity. The sensitivity of this assay was greater than that of a direct enzyme immunoassay in which rotaviruses of the appropriate serotype were adsorbed directly to the solid phase. When fecal extracts were concentrated threefold, this serotyping enzyme immunoassay was of equal specificity and approached the sensitivity of electron microscopy for rotavirus detection. This assay is simple and rapid and is suitable for serotyping the large numbers of isolates obtained from epidemiological studies and vaccine trials.
The etiology of acute diarrhea in children less than 42 months of age attending one pediatric hospital in Melbourne, Australia, was studied during a 7-month period encompassing the winter of 1984. Pathogens identified in 157 children treated as outpatients with mild disease were compared with those in 232 children hospitalized with severe disease. The pathogens (and frequencies among outpatients and inpatients, respectively) detected were rotaviruses (32.5 and 50.9%), enteric adenoviruses (8.9 and 7.4%), Campylobacter jejuni (7.2 and 1.3%), and Salmonella sp. (4.0 and 1.7%). Electropherotypes of rotavirus strains from outpatients and inpatients were compared. Two strains predominated during the 7 months of this study and were observed with equal frequency from outpatients and inpatients. Rotaviruses of the same electropherotype caused a wide spectrum of disease, with symptoms ranging from mild to severe, life-threatening diarrhea. The similarity of etiological agents identified from children with mild and severe forms of acute diarrhea suggests that the etiology of community enteric illness can be reasonably inferred from the etiology of inpatient disease in children in the same geographic area. During the winter epidemic period, the severity of symptoms associated with rotavirus infection in young children is likely to be determined by the inherent susceptibility of the host rather than by genetic differences in the strains of infecting rotaviruses.