Search

Human platelets do not synthesize nucleotides de novo (1) but have been demonstrated to possess salvage pathways utilizing adenine and adenosine (2,3). On the other hand, no evidence has been reported as yet for the presence of hypoxanthine-guanine phosphoribosyltransfe-rase (HGPRT) in human platelets.

Phosphoribosylpyrophosphate synthetase and hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activities were demonstrated in human and rabbit platelet lysates. Comparative measurement of HGPRT activity and adenine phosphoribosyltransferase activity showed the latter to be higher than the former in human platelet lysates and the reverse in rabbit platelet lysates.

Takayasu's arteritis is a chronic inflammatory arteriopathy of unknown cause. The pulseless phase of Takayasu's arteritis is preceded by a period of "prepulseless disease" when the patients suffer from systematic symptoms without obvious evidence of obstruction of larger arteries. Herein we report a unique case of Takayasu's arteritis presenting as sarcoidosis manifested by restrictive lung disease, hilar adenopathy and non-caseating granulomas of the skin. We are aware of only one report in which non-caseating skin granulomas were evident at the prepulseless phase of Takayasu's arteritis. However, in our patient the clinical picture was typical of sarcoidosis. Increased awareness of this possibility will lead to more frequent skin biopsies in patients with Takayasu's arteritis and nodular skin lesions, which may increase the number of reported cases with this combination.

Classical models of experimental autoimmune diseases, such as adjuvant arthritis entail the use of mycobacteria. Furthermore, BCG immunotherapy may be followed by arthritic symptoms. To test the infection-autoimmunity relationship of mycobacteria, we used monoclonal antibodies raised against M. tuberculosis and against DNA. Murine monoclonal anti-TB antibodies were found to react with ssDNA, dsDNA and other polynucleotides. Monoclonal anti-DNA autoantibodies derived from patients and mice with SLE bound to three glycolipids shared among all mycobacteria and derived from mycobacterial cell wall. Prior incubation of the antibodies with ssDNA and other polynucleotides or with glycolipid antigens inhibited binding. These results indicate that infecting mycobacteria share antigens with human tissue, thus accounting in part for the production of autoantibodies in mycobacterial infections.

The objective of this study was to prospectively determine the efficacy of the results of routine testing of thyroid functions in patients admitted to a general medical ward. Blood for thyroid function tests was drawn on admission as part of the laboratory screening panel from 270 consecutive patients. Fifty-one were excluded due to recognition of thyroid-related problems by the clinical staff. 138 patients (63%) had normal free thyroxin (FT4) levels, one patient had hyperthyroidism, 15 patients (6.8%) had laboratory primary hypothyroidism and 65 patients (29.6%) had equivocal results (FT40.9 ng/dL and TSH5.0 mmu/L). In eight out of 31 patients in the latter group, the thyroid releasing hormone (TRH) test revealed primary or secondary hypothyroidism. A total of 55 patients (25.1%) expired within one year. The mortality rate was significantly higher among the low FT4 patients (p0.01), and was independent of age and sex. We conclude that inclusion of FT4 in a laboratory screening panel will reveal a large patient population with abnormal results. However, establishing the diagnosis requires additional tests. Therefore, screening for occult hypothyroidism among a select population, not the acutely sick, populations may be more efficient.