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Biomedical subjects

A M Samuel

Publications and source records attributed to A M Samuel.

At least 73 records · Page 4Linked to original sources
PubMed1987

Increased sensitivity of triiodothyronine antibodies for radioimmunoassay after removal of endogenous antigen by simple laboratory procedures.

Conventionally produced antibodies against triiodothyronine (T3) are known to possess high amounts of endogenously produced T3 associated with them. We felt that such antibodies would work better for T3 radioimmunoassay (RIA) after prior removal of the antigen. With this in view, we attempted dissociation and subsequent removal of T3 from antisera by two different methods, viz. dialysis and alcohol extraction. It was possible to remove T3 to an extent of 77% by alcohol extraction and 60% by dialysis. Resultant antisera fail to demonstrate any increase in the titre. However, when standard curves were generated using these antisera, the assays became more sensitive and it was possible to detect T3 in concentrations as low as 6.25 pg. The affinity constants of these antisera calculated from the respective Scatchard plots were found to have increased after both dialysis treatment was well as alcohol extraction. This was thought to be due to rendering some of the high affinity binding sites on the antibodies free of antigen after treatment. Serum T3 levels were measured in 68 patients with various thyroid status using both treated as well as untreated antiserum. The difference between the average values of serum T3 concentration estimated using various antisera before and after the treatment was not statistically significant. Our results suggested that a simple procedure like stripping of antigen from antibodies could be of help for acquiring high affinity and high sensitivity antibodies for this purpose.

Antibodies↗
PubMed1987

Radioimmunoassay for detecting Mycobacterium tuberculosis antigen in cerebrospinal fluids of patients with tuberculous meningitis.

A biotin-avidin radioimmunoassay for detecting Mycobacterium tuberculosis antigen has been developed. The assay involves sandwiching mycobacterial antigens from sonicate preparations and cerebrospinal fluids between two antibodies produced in burros and rabbits. The reaction is amplified by using biotinylated antibody to rabbit IgG and 125I-labeled avidin. The assay has a sensitivity of 20 ng/ml and shows less than 5% cross-reactivity with six other mycobacteria. We studied patients with untreated tuberculous meningitis, patients with treated tuberculous meningitis, patients with nonbacterial meningitis, and patients with bacterial meningitis. Antigen was detectable in two of 56 control samples (40 ng/ml). Hence, samples with greater than or equal to 80 ng of antigen/ml were considered positive. In patients with untreated tuberculous meningitis, antigen levels ranged from 20 to 10,000 ng/ml, and 15 (79%) of 19 samples were positive. In the treated group, only two (10%) of 17 samples were positive. This test promises to be a rapid adjunct in the early diagnosis of tuberculous meningitis.

Antigens, Bacterial↗
PubMed1987

Radionuclide scintigraphy of the brain and ultrasound studies in tubercular meningitis.

The present study was undertaken to assess the usefulness of brain scintigraphy and ultrasound evaluation of changes described in tuberculous meningitis. Brain scans were done with Tc-99m DTPA in 127 cases of tuberculous meningitis (TBM) and ultrasound studies in 41 cases with open anterior fontanelles. The data show that 54/127 (42.5%) of cases had abnormal brain scans, of which 33/54 had cerebrovascular infarcts and 14/54 had tuberculomas, while the remaining cases had either subdural effusions or generalized increased activity. The cerebrovascular infarcts were more frequent in patients with acute onset of TBM with associated hemiplegias. The ultrasound studies indicated that 80% of all cases of TBM had a mild to severe dilatation of the ventricles. About 55% of cases had a dilatation of only the lateral ventricles while the remaining cases had a block of aqueduct or beyond the fourth ventricles. Increased intracranial pressure changes were associated with a higher incidence of severe ventricular dilatation. Noninvasive detection methods in the study of TBM are important not only from the point of view of diagnosis but also to understand and evaluate the pathological changes occurring in vivo during the disease process and to judge the progress and response to treatment. A combination of ultrasound and brain scans offers diagnostic accuracy comparable to CT. Apart from cost, the larger radiation doses resulting from CT studies preclude its routine use in pediatric subjects.

Brain↗
PubMed1987

A two-step radioimmunoassay for free triiodothyronine in serum.

Using a high-affinity solid-phase-bound antibody (Ka = 1.2 X 10(11) L/mol), we have standardized a two-step radioimmunoassay for free triiodothyronine (FT3) in serum, based on immunoextraction. The method was validated by comparison with an equilibrium-dialysis procedure (r = 0.96) involving RIA of T3 in the dialysate standardized with the same antibody and by a commercial (Liso-Phase, International-CIS) method. The two-step RIA could detect as little as 0.2 pg per milliliter. The mean CVs within and between assays were 9% and 12%, respectively. FT3 values measured in 30 normal adults ranged from 1.77 to 4.77 ng/L. Comparison with ratios of total T3 to thyroxin-binding globulin showed good agreement in normal subjects, pregnant women, and hypothyroid and hyperthyroid patients.

Female↗
PubMed1985

Circulating immune complexes in pulmonary tuberculosis.

The presence of circulating Immune complexes (CIC) in sera from patients with pulmonary tuberculosis was demonstrated by 3 techniques (a) latex agglutination (b) 3.5% PEG precipitation and determination of optical density (O.D.) at 280 nm and (c) radioimmunoassay (RIA) of CIC using bovine spermatozoa. 40 normal control sera and 100 T.B. patients sera were included in the study. 12% cases were positive for CIC by all the 3 methods mentioned above, 13% were negative by all the 3 methods and the remaining patients were positive by one or more methods of detection. To correlate the levels of CIC as detected by different techniques with the activity of the disease, patients were broadly grouped as (a) sputum positive and (b) sputum negative. Higher levels of CIC were obtained in sputum positive cases than sputum negative by all the 3 methods studied. While IgG, IgA and IgM were elevated in the CIC of T.B. patients, and IgG and IgA were also present in controls, IgM immunoglobulins were detected only in patients and not in controls. The effect of antitubercular treatment on the levels of CIC was also evaluated and it was found that the levels of CIC remained unchanged even after prolonged chemotherapy.

Adult↗
PubMed1984

Significance of circulating immune complexes in pulmonary tuberculosis.

In the present study we have tried to demonstrate circulating immune complexes (CIC) in sera from patients with pulmonary tuberculosis (TB) by three techniques; latex agglutination; 3.5% PEG precipitation and determination of optical density at 280 nm and RIA of CIC using bovine spermatozoa. About 40 normal control sera and 100 TB patients sera were investigated for the presence of CIC. Seventeen per cent cases of pulmonary TB were positive by latex agglutination while none of the control was positive. Levels of CIC as detected by PEG precipitation and RIA were significantly elevated in patients as compared to normal controls. While IgG, IgA and IgM were elevated in the CIC of patients, IgM immunoglobulins were detected only in patients and not in controls. Detection of CIC may at times be useful in diagnosis, prognosis and therapeutic monitoring of disease processes, but it is the characterization of immune complexes (IC) and identification of the specific components of these complexes which holds the greatest potential for better understanding of disease mechanisms. CIC were precipitated using 3.5% PEG from sera of patients suffering from TB. The specific anti-TB antibody component of complex was determined using S. aureus protein A as a solid phase, Anti-BCG antibody and 125I-labelled TB antigen. The specific TB antigen component of the IC was dissociated thermally from TB antibody and assayed by a radioimmunoassay technique developed in our laboratory. Patients were classified into two groups. Those those sputum was positive for Mycobacterium tuberculosis by smear and/or culture and those whose sputum was negative. The TB antigen concentrations of CIC was higher 19.1 +/- 2.3 ng/ml (mean +s.e.) in sputum positive cases, and 9.9 +/- 1.9 ng/ml in sputum negative cases as compared to 2.2 +/- 0.3 ng/ml in controls. Patient groups were significantly different from controls as well as from each other (P less than 0.001). Anti-TB antibody ratios were 11.7 +/- 1.48, 5.1 +/- 1.5 and 0.6 +/- 0.1 in sputum positive, sputum negative and controls. The significance of differences between the groups was P less than 0.001. The effect of treatment administered over a period of 12 weeks or more was evaluated. It was observed that in patients with persistent demonstration of M. tuberculosis in the sputum, the TB antigen and TB antibody levels of CIC were consistently high. In patients who responded to anti-tubercular drugs the TB antigen levels decreased progressively while TB antibody levels remained high.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Bacterial↗