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Biomedical subjects

A Raja

Publications and source records attributed to A Raja.

At least 55 records · Page 3Linked to original sources
PubMed1999

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.

Catalysis↗
PubMed1999

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.

Ankle Injuries↗
PubMed1998

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.

Base Sequence↗
PubMed1997

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.

Algorithms↗
PubMed1996

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.

Adolescent↗
PubMed1995

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.

Adolescent↗
PubMed1995

Characterization of mycobacterial antigens and antibodies in circulating immune complexes from pulmonary tuberculosis.

Circulating immune complexes (CICs) in serum samples from patients with pulmonary tuberculosis (bacteriologically positive [S+C+] and bacteriologically negative [S-C-]) and controls (NHC) have been measured by using C1q binding assay (C1qBA) and 3.5% polyethylene glycol precipitation and measurement of absorbance at 280 nm (PEG-OD 280). Although C1qBA did not show any difference between tuberculous and normal serum samples, PEG-OD 280 was significantly elevated in tuberculous samples. The effect of chemotherapy on CIC levels was studied. During the treatment, initially (for up to 2 months) there was a rise in CIC levels and later a fall, coinciding with bacterial clearance. Anti-purified protein derivative antibodies of class immunoglobulin G (IgG) and immunoglobulin M were measured in the serum samples and PEG precipitates. Anti-mycobacterial antibody measurement in CICs was more discriminatory between the groups than serum antibody. For characterization of the complexed antibody, the PEG precipitates were used in the Western blot and the patterns were compared. S+C+ CICs contained antibodies for a wide range of antigens ranging from 100 Kd to 10 Kd. However, none of the NHC-CICs contained antibodies for antigens < 70 Kd. Thus, when using the criterion of positivity for antibodies to antigens < 70 Kd as a marker for pulmonary tuberculosis, 24 of 24 (100%) of the S+C+ CICs were positive. Similarly, 11 of 16 (70%) of the S-C- CICs contained antibodies for antigens < 70 Kd.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Bacterial↗
PubMed1993

Serum adenosine deaminase activity in brain tumours.

Adenosine deaminase (ADA) activity in serum was estimated in 86 patients with intracranial tumours and 40 healthy volunteers. Although high ADA concentrations in biological fluids and tumour tissues were observed in several neoplastic conditions, there was no significant difference in the ADA in sera of brain tumour patients when compared to the control values. Therefore, cell-mediated immunity probably does not play a significant role in brain tumours.

Adenosine Deaminase↗
PubMed1993

Urinary excretion of 6-hydroxymethylpterin in brain tumours.

The urinary 6-hydroxymethylpterin(Pt-6-CH2OH) excretion was determined in 87 patients with brain tumours and in 50 control patients. The Pt-6-CH2OH levels were significantly elevated in all patients with tumours. No difference was observed when malignant tumours were compared with benign neoplasms. Following therapy, the Pt-6-CH2OH levels were partially reduced when compared with control patients and their pre-operative values.

Adolescent↗
PubMed1993

Urinary excretion of pseudouridine in patients with brain tumours.

Elevated urinary levels of modified nucleosides, especially pseudouridine (psi), have been observed in patients with a variety of malignant neoplasms. In this report, the urinary psi levels were estimated by high performance liquid chromatography in 93 patients with brain tumours and in 40 age and sex matched controls. The psi levels were found to be excreted in equal amounts in the control and the tumour groups. There was no significant difference in psi when patients with malignant diseases were compared with those with benign tumours. Following therapy, the psi levels remained unchanged when compared to the controls and their preoperative values. It is concluded that urinary psi concentration is not a useful marker for brain tumours.

Adolescent↗
PubMed1992

Serum immunoglobulins in brain tumours.

Immunoglobulin level in the sera of 62 patients with intracranial space occupying lesions was assayed using the radial immunodiffusion method. Serum IgM levels showed a highly significant increase in all types of brain tumour when compared to controls. Serum IgG levels were also increased in benign as well as malignant cases. Serum IgA levels were high only in benign cases. Hence, increased serum Ig levels may be of prognostic value in these cases.

Adolescent↗
PubMed1992

Elevation of serum ceruloplasmin levels in brain tumours.

Serum ceruloplasmin levels have been estimated in 80 patients with various intracranial space occupying lesions and in 30 controls. The ceruloplasmin levels were significantly increased in all brain tumours except in meningiomas. After therapy, the ceruloplasmin levels were still significantly increased when compared to controls and their respective preoperative values. However, the rise in levels of ceruloplasmin in malignant tumours compared to benign was statistically not significant. It is concluded that ceruloplasmin may have a role to play as an acute phase reactant protein in brain tumours.

Adolescent↗
PubMed1991

Otogenic brain abscess in childhood.

Brain abscesses are quite rare complications of middle ear infections. Although temporal lobe abscesses are more common than cerebellar abscesses, the converse was found to be true in our series of 10 cases. Eight cases of cerebellar abscess and 2 cases of temporal lobe abscess in the paediatric age group were reported including 4 cases of latent brain abscesses which manifested themselves after mastoidectomy for middle ear infection. Brain abscess is by far the most serious of otogenic complications.

Adolescent↗
PubMed1988

The detection by immunoassay of antibody to mycobacterial antigens and mycobacterial antigens in bronchoalveolar lavage fluid from patients with tuberculosis and control subjects.

Bronchoalveolar lavage (BAL) samples from patients with pulmonary tuberculosis and from control subjects were studied using direct and inhibition enzyme-linked immunosorbent assay (ELISA) for the detection of IgG and IgA antibody to Mycobacterium tuberculosis culture filtrate and purified antigen 5 and for the detection of mycobacterial antigens. The IgG and IgA antibodies were found in the majority of samples from tuberculous patients. The IgG titers were higher than were IgA titers. Substantial nonspecificity was observed for antibodies to crude M tuberculosis culture filtrate. Antibodies to purified M tuberculosis antigen 5 were more specific. The detection of antibody in BAL did not offer advantages over previously described serodiagnostic assays. Antigen was found in some BAL samples from tuberculous patients. Greater specificity was observed with an assay based on purified antigen 5 than on crude mycobacterial culture filtrate.

Adult↗