Biomedical subjects
A Raja
Publications and source records attributed to A Raja.
Pattern recognition technique in immunological antigenic tests to identify Mycobacterium tuberculosis infection.
UNLABELLED: The importance of a diagnostic test that is simple and quick to identify Mycobacterium tuberculosis infection needs no emphasis. The tuberculin skin test (TST - 1 TU RT23) is the diagnostic tool for identifying M. tuberculosis infection at present. The test reaction on the skin is measured after 48-72 h. It is observed that often multi-modes are seen, when the reactions are drawn as a graph and the bimodality is seen very feebly. Because of the difficulties in the administration of TST, several serological tests were developed over three decades, but none of the studies showed the desired results. One study to evaluate purified protein derivative (PPD) antigen resulted in a claim of 80% sensitivity and 4% false-positivity rate (14), while other researchers were not able to obtain similar results. In addition, several problems were encountered due to the non-availability of antigens, and data analyses from an ELISA-based diagnostic test showed considerable overlap of distributions of optical density (OD) values among patients and healthy individuals (10). Classical statistical techniques cannot explain the cause of these overlaps. Hence, an attempt is made in this article to resolve these difficulties by the pattern recognition technique (PRT). The technique lies in splitting the data into clusters using a supervised algorithm. The data set is normally split into a training set, a test set and a validation set. The PRT gets "trained" through the training data set until the infected and uninfected groups of individuals are correctly classified. The training occurs based on an algorithm on the training set. On successful completion of the training, this technique is further tested and validated in the respective data sets. SETTING: A total of 273 finger-prick specimens were collected from five categories (Al, A2, B, C, D, E) of subjects not vaccinated with (bacille Calmette Guerin) (BCG) from Trivellore BCG Trial area adopted by the Tuberculosis Research Center, Chennai, India. OBJECTIVE: The study was conducted with the primary aim of evaluating purified antigens--r38 kDa, PPD and 30 kDa--for their usefulness as diagnostic tools and to test the applicability of the PRT in the evaluation of diagnostic tests. Individuals in two main categories (definitely not infected categories Al, A2 and D, and definitely infected categories B, E and C based on reaction to TST) were assembled for the purpose. RESULTS: The overall PRT performance of 30 kDa was 72.3% sensitivity and 90.9% specificity for identifying M. tuberculosis infection, while the r38 kDa antigen recorded a sensitivity of 73.8% and a specificity of 84.6%. In the case of PPD, the results were not promising. CONCLUSION: This paper on ELISA-based diagnostic tests attempts to implement an optimal decision support system through PRT that would identify the outcome (as infected or non-infected) based on the OD values. The PRT was able to predict the outcome for individual suspects. Further, Kullback-Leibler distance measurement has validated the PRT in distinguishing infected individuals from healthy subjects (based on the OD values).
Contemporary management of subarachnoid hemorrhage and vasospasm: the UIC experience.
BACKGROUND: Cerebral vasospasm is a well-known and serious complication of aneurysmal subarachnoid hemorrhage. The means of monitoring and treatment of vasospasm have been widely studied. Each neurosurgical center develops a protocol based on their experience, availability of equipment and personnel, and cost, so as to keep morbidity and mortality rates as low as possible for their patients with vasospasm. METHODS: At the University of Illinois at Chicago, we have developed algorithms for the diagnosis and management of cerebral vasospasm based on the experience of the senior authors over the past 25 years. This paper describes in detail our approach to diagnosis and treatment of aneurysmal subarachnoid hemorrhage and vasospasm. Our discussion is highlighted with data from a retrospective analysis of 324 aneurysm patients. RESULTS: Over 3 years, 324 aneurysms were treated; 185 (57%) were clipped, 139 (43%) were coiled. The rate of vasospasm for the 324 patients was 27%. The rate of hydrocephalus was 32% for those patients who underwent clipping, and 29% for those coiled. The immediate outcomes for those who underwent clipping was excellent in 35%, good in 38%, poor in 15.5%, vegetative in 3%, and death in 8% of the patients. For those who underwent coiling the immediate outcome was excellent in 64%, good in 14.5%, vegetative in 2.5%, and death in 14.5% of the patients. These statistics include all Hunt and Hess grades. For those patients who underwent clipping, 51% were intact at 6 months follow-up, 15% had a permanent deficit, 10% had a focal cranial nerve deficit, and 2% had died from complications not directly related to the procedure. For those patients who had undergone coiling, 75% were intact at 6 months follow-up, 12.5% had a permanent deficit, and 12.5% had a cranial nerve deficit, with no deaths. CONCLUSIONS: The morbidity and mortality of cerebral vasospasm is significant. A good outcome after aneurysmal subarachnoid hemorrhage is dependent upon careful patient management in the preoperative, perioperative, and postoperative periods. The timely work-up and aggressive treatment of neurological deterioration, whether or not it is because of vasospasm, is paramount.
Spontaneous regression of a large lumbar disc herniation: report of an illustrative case.
A case of spontaneous regression of a large herniated disc at the lumbar level is presented. The disc regression correlated with clinical improvement and was documented on serial MRI studies. Although the phenomenon of spontaneous disappearance of decrease in size of herniated disc fragments is well known, the exact mechanism underlying this process remains unclear. This report discusses three possible explanations for disc regression: retraction into the intervertebral space, dehydration/shrinkage, and resorption due to inflammatory reaction.
Specific and early detection of IgG, IgA and IgM antibodies to Mycobacterium tuberculosis 38kDa antigen in pulmonary tuberculosis.
The objective was to apply the purified 38kDa protein antigen of Mycobacterium tuberculosis in ELISA to estimate the IgG, IgA and IgM antibody levels in sera and circulating immune complexes of tuberculosis patients. Sera from smear and culture positive tuberculosis patients were positive for anti 38kDa IgG, IgA and IgM antibodies, with a sensitivity of 61%, 30% and 10%, respectively, and with a specificity of 100% for IgG. The sensitivity of the test improved to a level of 68% for IgG+IgA and of 71.4% for IgG+IgA+IgM without significantly compromising the specificity (IgG of 100%, IgG+IgA of 96%, IgG+IgA+IgM of 90%). Among the smear, culture-negative but X-ray-positive cases, 60% were serum positive for IgG antibody, while in smear-negative but culture-positive cases, 54% were positive for IgG antibody. Measurement of 38kDa antibodies showed a greater than 95% sensitivity in smear and culture-positive, and smear-negative and culture-positive patients, through a combination of assays for serum IgG and circulating immune complex antibodies, while the specificity was 100%.
Serologic response to a secreted and a cytosolic antigen of Mycobacterium tuberculosis in childhood tuberculosis.
BACKGROUND AND AIM: Bacteriologic diagnosis of childhood tuberculosis is difficult, and alternate methods are needed. The utility of a serologic test for major secretory antigen (30 kDa) and a cytosolic antigen (16 kDa) of Mycobacterium tuberculosis was evaluated for the diagnosis of tuberculosis in children. METHODS: Enzyme-linked immunosorbent assay was used. Specific IgG, IgA and IgM antibodies were measured in the sera from 26 clinically and/or bacteriologically diagnosed cases of childhood tuberculosis and 61 normal children. RESULTS: Anti-IgG antibodies alone, against both 30- and 16-kDa antigens, were detected in 65.4% of patients. However, by combination of all three isotypes, increased sensitivities of 84.6 and 73%, with a specificity of 96.7% each, were obtained for 30- and 16-kDa antigens, respectively. CONCLUSIONS: We found good specificity and reasonably good sensitivity for detection of antibodies by enzyme-linked immunosorbent assay to 30-kDa antigen alone. The 16-kDa antigen did not perform as well.
In vitro strand transfer from broken RNAs results in mismatch but not frameshift mutations.
An in vitro system to compare the fidelity of strand transfers from truncated vs full-length RNAs was constructed. A donor RNA, on which reverse transcriptase (RT)-directed DNA synthesis was initiated, shared homology with an acceptor RNA, to which DNAs initiated on the donor could transfer. All RNAs were derived from the N-terminal portion of the alpha-lac gene. On full-length donors, transfers occurred when DNAs migrated to the acceptor prior to being completed on the donor. On donors that were truncated, most transfers occurred after DNAs reached the end of the donor. Transfer products were amplified by PCR and used to replace the corresponding region in a vector containing the alpha-lac gene. Transformed Escherichia coli were screened for alpha-complementation by blue-white phenotype analysis, with white colonies scored as those with errors in alpha-lac. These errors were derived from RT synthesis and strand transfer. The mutant colony frequency approximately doubled for transfer products derived from truncated donors (0.026+/-0.005 vs. 0.053+/-0.011 (three experiments +/- SD), for full-length vs. truncated, respectively). The increases resulted from additional non-template-directed bases (mostly thymidines) added to the DNAs before transfer. Sequence analysis of DNAs synthesized on truncated donors showed that about 60% had additions (20/34); however, those without additions transferred at a much higher rate than those with. Transfer of the DNAs with additions always resulted in substitutions; no frameshifts were observed. Results are consistent with RT adding nontemplated nucleotides at template termini. Transfer and subsequent extension of these products is severely inhibited relative to products without additions. The potential relevance of these findings to retrovirus replication is discussed.
Role of antioxidant enzymes in brain tumours.
Erythrocyte antioxidant enzymes were analysed in 100 patients with intracranial neoplasm and in 47 controls. There was a significant decrease in RBC glutathione reductase (GRx) and superoxide dismutase (SOD) activity in most types of brain tumor cases. Patients with acoustic neurinoma showed a significant reduction in selenium-dependent glutathione peroxidase (Se-GPx) activity. A decrease in catalase (CT) activity was seen in most of the brain tumor patients but remained statistically insignificant when compared to controls. A significant increase in plasma ceruloplasmin concentration was observed in patients with glioma. These enzymes were also studied in 27 post-treatment cases. GRx activity returned to normal levels in these patients. RBC SOD and plasma ceruloplasmin levels showed a tendency to return to normal. Hence, a marked decrease in the antioxidant enzymes may have a role in the genesis of considerable oxidative stress in patients with brain tumors.
Lipid peroxidation in brain tumours.
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Transcultural oral health care: 3. Dental care and treatment during the fast of Ramadan.
The aim of this paper is to highlight issues that may affect dental treatment and care of Muslim patients when they are fasting during Ramadan. Recommendations are provided on how to provide culturally sensitive oral health care for this community. By taking into account the beliefs and wishes of the individual, dentists will provide a service that is acceptable and appropriate to both the Muslim community and individual Muslims.
Production & characterization of monoclonal antibodies to Mycobacterium tuberculosis.
BACKGROUND & OBJECTIVES: Monoclonal antibodies (MAbs) against Mycobacterium tuberculosis H37Rv culture filtrate (CF) were raised by immunizing BALB/c mice and characterization was done. Attempts have been directed towards identifying mycobacterial antigens in biological fluids by employing polyclonal and monoclonal antibodies specific for M. tuberculosis. Immunohistologic studies, using MAbs for the localization of whole or fragmented bacilli in the biopsy specimens were also carried out. METHODS: Intrasplenic IS and intraperitoneal i.p. routes of immunization, were compared. The MAbs were characterized for their isotype, binding specificity, nature of binding epitope, reactivity in immunoassays etc. RESULTS: IS and i.p. routes of immunization, were compared and i.p. was found superior. Ten MAbs designated TRC 1-10 were produced. Of these, 7 MAbs, TRC 1-7 reacted with the 30/31 kDa doublet (antigen 85 complex), TRC 8 with 12 kDa in addition to 30/31 kDa and TRC 9 and 10 with the 24 and 12 kDa antigens respectively. Six MAbs were classified as broadly cross reactive and 2 showed limited cross reactivity. TRC 8 and 10 showed species specificity. Employing TRC 8 in sandwich ELISA, antigen was detected in sera from 17 of 25 pulmonary tuberculosis patients and 3 of 20 controls. TRC 8 was found to be useful in detecting antigens specifically in M. tuberculosis and M. leprae infected tissues, by immunoperoxidase staining. INTERPRETATION & CONCLUSION: TRC 8 was found to be restricted in its reactivity to M. tuberculosis complex and M. leprae. TRC 8 may prove useful in immuno-diagnosis of tuberculosis.
Kinetic analysis of the effect of HIV nucleocapsid protein (NCp) on internal strand transfer reactions.
The mechanism of HIV reverse transcriptase (RT) catalyzed strand transfer synthesis (i.e., switching of the primer to a new template) from internal regions on RNA templates in the presence and absence of HIV nucleocapsid protein (NCp) was investigated. Two different systems each consisting of DNA-primed RNA donor (on which primer extension initiated) and acceptor (to which DNAs initiated on the donor could transfer) templates were used to determine kinetic parameters of strand transfer. The donor and acceptor shared an internal region of homology where homologous strand transfer could occur. The rate of strand transfer at various acceptor concentrations was determined by monitoring the production of transfer products over time. These rates were used to construct Lineweaver-Burk plots. In each system, NCp increased the Vmax about 3-fold while the Km for acceptor template was decreased severalfold. NCp's effects on RT extension ranged from no effect to inhibition depending on the primer-template used. The lowered Km shows that NCp increases the affinity of the acceptor template for the transferring DNA. Vmax increases despite the inhibition of RT extension. The increased Vmax implies a stimulatory mechanism that cannot be mimicked by high acceptor concentrations. Therefore, NCp does not act by merely increasing the effective concentration of nucleic acids.
Complex regional pain syndrome.
Complex regional pain syndrome is a chronic pain syndrome that is often instigated by postoperative or post-traumatic events. The disease process can progress through three stages, the first of which tends to respond best to treatment. A review of the literature is presented, followed by a report of a patient who developed symptoms of complex regional pain syndrome following a water-skiing accident.
High fidelity of internal strand transfer catalyzed by human immunodeficiency virus reverse transcriptase.
A system to study the fidelity of internal strand transfer events was constructed. A donor RNA, on which reverse transcriptase (RT)-directed DNA synthesis was initiated, shared homology with an acceptor RNA, to which DNAs initiated on the donor could transfer. The homology occurred over a 119-base internal region of the donor which coded for the N-terminal portion of the alpha-lac gene. Polymerase chain reaction (PCR) was used to amplify DNA synthesis products. The PCR products were then digested with PvuII and EcoRI and ligated into a vector which had this same region excised. Transformed Escherichia coli were screened for the ability to produce a functional beta-galactosidase protein by blue-white phenotype analysis with white colonies scored as those with errors in alpha-lac. Products synthesized on the donor were used to assess the error rate of human immunodeficiency virus-RT while products transferring to and subsequently extended on the acceptor (transfer products) were used to monitor transfer fidelity. Human immunodeficiency virus-RT made approximately 1 error per 7500 bases copied in the assay. Nucleocapsid protein (NCp), although stimulating strand transfer 3-fold, had no effect on RT fidelity. Transfer products in the absence of NCp had essentially the same amount of errors as donor-directed products while those produced with NCp showed a slight increase in error frequency. Overall, strand transfer events on this template were highly accurate. Since experiments with other templates have suggested that transfer is error prone, the fidelity of strand transfer may be highly sequence dependent.
Neural network method to determine the vigilance levels of the central nervous system, related to occupational chronic chemical stress.
The effects of chronic toxic occupational factors and functional disorders of the central nervous system (CNS) in chemical industry were studied. These factors cause various stages of chronic chemical stress on the human CNS together with changes of the vigilance levels. On the basis of QEEG data analysis and psychometric tests we identified three stages of occupational chemical stress syndromes according to the CNS vigilance level (ordered from light to severe): hypersthenic syndrome, hyposthenic syndrome, and organic psychosyndrome. Each syndrome is characterized by specific changes in the QEEG data. A perceptron-based neural network was developed for the classification of the QEEG data to one of the above-mentioned syndrome classes. The data of 77 patients and 10 healthy subjects were selected to test the algorithm. Different combinations of the QEEG data as input features to the classifier were chosen. The most reliable classification was obtained when QEEG data measured during the visual stimulation of the CNS were used. However, sometimes the algorithm was unable to solve the classification problem, or it took a very long time to train the perceptron. In part, difficulties arose from using a perceptron-based algorithm, which can classify only linearly separable data.
Molecular variants of epidermal growth factor in malignant astrocytoma.
The present study has measured EGF levels in primary brain tumor tissues. EGF levels were measured by specific radioimmunoassay (RIA) and further analyzed by reversed-phase high performance liquid chromatography (RP-HPLC) followed by RIA and radioreceptor binding. The levels of EGF-like immunoreactivity (EGF-LI) in astrocytoma-IV tumors were fourfold greater than those in normal brain tissues. In astrocytoma-II and astrocytoma-III tumors, however, levels of EGF-LI were not different from those in normal brain. HPLC analysis of extracts from normal brain tissue and astrocytoma-II showed one peak of EGF-LI that coeluted with standard human EGF (retention time 22 min). Interestingly, EGF-LI in extracts of astrocytoma-IV tumors eluted in two distinct peaks with retention times of 24 and 26 min (Astro-A and Astro-B, respectively). Materials in both Astro-A and Astro-B peaks reduced the specific binding of [125I]hEGF to EGF receptors in human placental membranes. These studies demonstrate elevated levels of EGF-LI in malignant astrocytoma, but not in benign tumors. Furthermore, two different EGF-like molecules that are different from native EGF are present in malignant astrocytoma.
Circulating immune complexes in intracranial neoplasms.
The levels of circulating immune complexes (CIC) were assayed in the sera of 109 patients with intracranial space occupying lesions. The CIC levels were significantly increased in all the brain tumours. After treatment, the CIC levels were still significantly increased when compared to the controls but showed no change when compared to their respective pre-operative values. Further, no change was observed in the CIC levels between the malignant and benign tumour case. Moreover, in brain tumours, 90% of the CIC precipitate consisted of IgG. However, the CIC levels fail to prognosticate the process of the disease in these patients.