Isolation of low molecular mass proteins from renal stones

Abstract

Recent investigations show that a great deal of effort is being put to develop a specific test which could be effectively used to diagnose meningitis and which could also be helpful in differential diagnosis of infectious diseases of the central nervous system [ 1-31. In this context several constituent proteins of cerebrospinal fluid (CSF) have been evaluated to establish their possible correlation with bacterial meningitis [ 1, 4, 51. We previously evaluated the use of ultra-thin-layer SDSlPAGE as a rapid method to analyse CSF proteins, as qualitative changes occurring in these might be of some value in the diagnosis of bacterial meningitis [6]. In this communication we report the presence of two low molecular mass proteins which appear to be specific for bacterial meningitis. CSF samples from 1 12 patients with bacterial meningitis were examined by ultra-thin-layer SDS/PAGE using the procedure described elsewhere [6]. The total protein concentration in these CSF samples was between 21 and 3500 mg/dl (mean 232 mg/dl). This indicates that total protein concentration in this disease is inconsistently raised, thus making it a highly unreliable parameter for diagnostic purposes. When these CSF samples were analysed by SDS/ PAGE (Fig. l a ) they showed a consistent pattern of protein bands despite the fact that their total protein concentrations were not comparable in many cases. In addition to the protein bands present at M , 66000, 55000 and 25000 which seemed to be the common feature of CSF samples, the most noticeable finding was the presence of two low molecular mass protein species at approximate M , 12000 and 15000. In 91 out of 112 samples of bacterial meningitis these protein bands were clearly visible. The same combination of these two bands was not detected in the CSF sample of viral meningitis and other disorders of the nervous system. To further investigate whether these proteins exist as monomeric proteins or are subunits of each other, the same samples were also subjected to PAGE in the absence of detergent and reducing agent. Fig. I (h) shows the electrophoretic profiles of CSF proteins from individuals with bacterial meningitis. On this system, those low molecular mass protein bands were not present. Instead, a single band at approximate M , 30 000 was present which could possibly be a dimer of the two low molecular mass proteins described earlier on SDS-gels. Attempts are now being made to establish the physicochemical characteristics of these proteins. Our results show that the specificity of these low molecular mass proteins was 81%, which could possibly place these M, 66000 -