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J Tharakan

Publications and source records attributed to J Tharakan.

32 records · Page 2Linked to original sources
PubMed1991

Comparison of the performance of immunosorbents prepared by site-directed or random coupling of monoclonal antibodies.

The majority of methods used to prepare immunosorbents immobilize antibodies through their reactive amino acid residues. The bound antibody activity of these immunosorbents is low. Hydrazide-based matrices couple antibodies through carbohydrate chains frequently located in the Fc region. This paper reports a comparative study of the performance of immunosorbents prepared by cyanogen bromide or hydrazide immobilization methods. The experiments utilized murine monoclonal antibodies to the human plasma proteins Factor IX or Protein C. The antibodies were immobilized at low densities to beaded agarose matrices which had similar properties. The hydrazide immunosorbents had binding efficiencies which were lower (anti-Factor IX) or up to 1.6-fold higher (anti-Protein C) than comparable cyanogen bromide coupled gels. However, there was no improvement in performance due to lower recoveries of bound protein from the hydrazide gels. Control experiments demonstrated that oxidation of antibody which is required for its coupling to hydrazide gels had no effect on antibody binding to antigen. Our results indicate that, as with cyanogen bromide coupling methods, site-directed immobilization through carbohydrate residues results in a restricted ability to bind to antigen. Both monoclonals were found to contain carbohydrate in their Fab' regions through which coupling may have occurred. The frequency of carbohydrate in the Fab region and the ability to control glycosylation at these sites are factors which may impact the utility of carbohydrate-directed immobilization of antibodies.

Antibodies, Monoclonal↗
PubMed1990

Development of an immunoaffinity process for factor IX purification.

An immunoaffinity process based on monoclonal antibody (MAb) to factor IX (FIX) has been developed. Initially, vitamin-K-dependent proteins from cryoprecipitate-poor plasma are isolated on DEAE-Sephadex. The eluate is applied to an immunoaffinity column that utilizes a divalent metal-ion-dependent MAb directed against FIX. After washing the column with high salt in the presence of magnesium ion, the FIX is eluted using a citrate- or EDTA-containing buffer. Coagulation assays and Western blots show no detectable amounts of any contaminating proteins. Purity of the FIX product is established using reduced and nonreduced Coomassie-stained SDS-PAGE and HPLC. The N-terminal 20 amino acids of the single peak of the HPLC were shown to be identical to those reported for FIX. The process shows no detectable leakage of monoclonal antibodies (MAb), efficient utilization of MAb, and provides yields greater than 95%. The use of solvent/detergent treatment as a potential viral inactivation methods is incorporated in the process. Studies with tritiated Triton X-100 indicate that the detergent can be washed out of the MAb column so that less than 1 ppm (total) Triton X-100 coelutes with the FIX.

Amino Acid Sequence↗
PubMed1990

Small volume plasma exchange in Guillain-Barre syndrome: experience in 25 patients.

The impact of small volume plasma exchange (PE) on the treatment of Guillain-Barre syndrome (GBS) was studied by comparing 25 patients treated with PE since 1982 with 25 historic controls treated without PE prior to 1982. Small volume PE was done by removing 10-15 ml plasma/kg body weight daily till the progression of the disease was arrested or recovery started. The PE group started recovering earlier (median 3 days, compared to 17.5 days in controls, 2P = 0.01), attained better clinical grades at the end of the 1st and 3rd months (2P = 0.001), and took much shorter time to recover by one clinical grade (median 15 days, compared to 53 days in controls, 2P = 0.01). The median duration of ventilation among the surviving patients was shorter in the PE group (8 days compared to 24.5 days, 2P = 0.10) and total number of complications was less in the PE group (15 events compared to 22 in the controls, 2P = 0.05). Three months after the onset of neuropathy, 13/25 controls were still bed bound, whereas only 4/25 in the PE group remained in that grade (2P = 0.02). There was no significant difference in the mortality rate in two groups (2P = 0.09), but the difference was significant in the subgroup of patients who were ventilated (2P = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Plasma exchange for Guillain-Barré syndrome.

The impact of plasma exchange (PE) on the treatment of severe Guillain-Barré syndrome (GBS) was studied by comparing all the 16 patients treated with PE in a London teaching hospital between January 1985 and August 1987, with 64 historical controls drawn from a series of patients observed during a prospective study in South East England in 1983 and 1984. There were no GBS-related deaths in the PE treated group but seven in the historical controls (2P = 0.39). The median duration of ventilation was only 20 days (range 7-64) in the PE group compared with 36 days (range 14-365) in the surviving patients in the control group (2P = 0.06, 95% confidence interval of difference in medians -36 to 0 days). The PE group walked earlier without aid (median 55.5 compared with 86 days, 2P = 0.04, 95% confidence interval of difference in medians -88 to -2 days). Three months after the onset of neuropathy all PE treated patients were able to walk with support or better, whereas 19 of the surviving historical controls were unable to walk even with support (2P = 0.009). The costs of PE were offset by savings in intensive care unit and hospital expenditure.

Adult↗
PubMed1982

Ipsilateral seizures.

Seven patients who had partial elementary seizures on the same side as the cerebral lesion are described. In six patients the seizures were partial motor, and one patient had seizures which ware partial elementary with sensory symptomatology. Four patients had frontal lesions, two parietal, and one parietotemporal. Five patients out of seven had lesions in the right cerebral hemisphere. There were three cases with astrocytoma, two with infarction, and one each with meningioma and tuberculoma. The clinical significance and pathophysiological mechanisms of this rare ipsilateral sign are discussed.

Adolescent↗
PubMed1982

Mitral valve prolapse and cerebrovascular accidents in the young.

The incidence of stroke in the young is reported to be high in India. The role of the mitral valve prolapse (MVP) syndrome in these patients is not clear. A prospective study over a period of 1 year was carried out in order to evaluate the role of MVP in cases of stroke occurring in patients below the age of 40 years. Of the 38 cases of stroke in the young seen during this period, well-recognised risk factors of stroke could be detected in 17. MVP confirmed by M-mode echocardiography was seen in 13% of all stroke patients and in 23.8% of those in which there were no other risk factors. The incidence of MVP was much higher if only the clinical criteria for diagnosis were used. We believe that MVP is a significant risk factor in younger stroke patients, and, in such cases, merits investigation. The probable pathogenic mechanisms and therapeutic implications are discussed.

Adolescent↗
PubMedDate not supplied

Clinical and angiographic profile and follow-up of myocardial bridges: a study of 21 cases.

Myocardial bridging describes an angiographic entity, which is any degree of systolic narrowing of a coronary artery observed in at least one angiographic projection. Among the cineangiograms of 3200 patients reviewed, there were 21 cases (19 males) of myocardial bridges--incidence of 0.6 percent. Of these, seven had hypertrophic cardiomyopathy, six had atherosclerotic coronary artery disease and remaining eight had no evidence of either. All 21 patients had myocardial bridges in proximal or mid left anterior descending coronary artery. In addition, one case of hypertrophic cardiomyopathy had whole posterior descending coronary artery under a myocardial bridge. Another case of hypertrophic cardiomyopathy had a short normal segment of 5 mm inside a long myocardial bridge of 35 mm (tandem myocardial bridges). The length of the bridges varied from 10 to 35 mm (mean 24.5 +/- 4.5 mm) and diameter stenosis during systole varied from 40-90 percent (mean 70 +/- 8%). Two patients had large saccular coronary aneurysms proximal to the muscle bridge. Four of the eight patients who had neither hypertrophic cardiomyopathy nor coronary artery disease presented with acute anterior wall myocardial infarction and three of them had regional wall motion abnormality of left descending territory. Of the six patients who had coronary artery disease, one had 60 percent left descending artery lesion and two had recanalized segments proximal to the bridge. Five of the above six patients had significant stenosis of other coronary vessels. Four patients were lost to follow-up (mean period 3.4 +/- 2 years). In the coronary artery disease group, one patient underwent coronary artery bypass graft surgery for 3-vessel disease including graft to left descending artery and one developed inferior wall myocardial infarction. The patients in the hypertrophic cardiomyopathy group and "no hypertrophic cardiomyopathy-no coronary artery disease" group were free of events at last follow-up. Long-term prognosis of isolated myocardial bridges appears to be excellent. Degree of systolic narrowing or length of myocardial bridge does not correlate with event rates on follow-up.

Adult↗
PubMedDate not supplied

Coronary artery ectasia: angiographic, clinical profile and follow-up.

Out of 3200 coronary angiograms we reviewed, there were 144 cases of coronary ectasia--an incidence of 4.5 percent. Among these, 122 were associated with atherosclerotic coronary artery disease, i.e. coronary stenosis more than 50 percent (group A) and 22 not associated with coronary artery disease (group B). The patients in groups A and B were compared with age- and sex-matched patients (group C) (n=100) who had coronary artery disease alone without ectasia. The incidence of ectasia was not increased in patients with thoracoabdominal aortic aneurysm i.e. 2/154 (1.8%) or in patients with peripheral occlusive vascular disease i.e. 5/161 (3.1%). Ectasia was typed according to a modified version of the criteria proposed by Markis et al. Type II was the commonest, followed by type I, III and IV. Right coronary artery was the most commonly involved vessel by ectasia followed by left circumflex, left anterior descending artery and left main coronary artery. Diffuse ectasia was seen more frequently in right coronary artery and localised ectasia in left anterior descending artery. Patients in groups A and B had similar epidemiological characteristics, though more patients with ectasia alone (group B) had better left ventricular function and negative stress tests. The patients in group A had a similar incidence of previous myocardial infarction, coronary risk factor profile, treadmill exercise test status and severity of coronary artery disease when compared to group C. On a mean follow-up of 3+/-1.2 years, all the three groups had similar event rates.

Adult↗
PubMedDate not supplied

A correlative study of the functional class and hemodynamic status following intracardiac repair of tetralogy of Fallot.

An attempt was made to correlate the NYHA Functional class with the hemodynamic status of 196 patients at an average of 21.2 months following the intracardiac repair of tetralogy of Fallot. 171 patients were in Functional class I (87.2%), 9 in class III (4.5%), 5 in class II (2.5%) and 11 in class IV (5.6%). Right and left heart catheterisation and cardiac angiography revealed the hemodynamic status of these patients to be excellent in 92 (46.4%), good in 37 (18.8%), satisfactory in 6 (3.0%) and unsatisfactory in 61 (31.6%). Whereas all patients in Functional class II, III and IV had unsatisfactory hemodynamic findings, patients in Functional Class I were hemodynamically heterogeneous and included excellent (53.8%), good (21.6%), satisfactory (3.5%) and unsatisfactory (21%) groups. The surgical technique did not seem to determine the functional status. While early reoperation is advisable for patients with functional disability, caution is necessary in considering reoperation for patients in Functional class I who have hemodynamic findings which are classified as unsatisfactory.

Adolescent↗
PubMedDate not supplied

Assessment of severity of aortic stenosis by continuous wave Doppler echocardiography.

Fifty consecutive patients with aortic stenosis were evaluated by continuous wave Doppler echocardiography for assessment of the transaortic gradient. The Doppler derived gradients were compared with the gradients measured at cardiac catheterisation. Excellent correlation was found between the Doppler and catheterisation findings for the maximum instantaneous gradient (r = 0.92) and the mean systolic gradient (r = 0.84). The maximum, midsystolic and late systolic Doppler gradients also showed a good correlation with the peak to peak catheter gradient. The maximum Doppler velocity however, showed overestimation of the peak to peak gradient in the presence of mild aortic stenosis (predictive accuracy 86%). The midsystolic Doppler velocity showed the highest predictive accuracy (94%) for the detection of severe aortic stenosis. No case of severe aortic stenosis was missed by Doppler using either the maximum or midsystolic Doppler velocity. These findings indicate that continuous wave Doppler ultrasound provides a reliable estimate of the gradient in patients with aortic stenosis.

Adolescent↗