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Biomedical subjects

A S Daar

Publications and source records attributed to A S Daar.

At least 19 recordsLinked to original sources
PubMed1996

HLA antigens in an Omani population with dilated cardiomyopathy.

We have investigated the frequency of HLA antigens in 50 Omanis with idiopathic dilated cardiomyopathy to establish whether there are ethnic/racial differences in the reported HLA associations with this disease. There were no statistically significant HLA-A, B, C, DR or DQ antigen frequency differences between the patients and 247 healthy Omanis. THe reported association of HLA-DR4 with idiopathic dilated cardiomyopathy in the Caucasian population does not apply to the Omanis. This confirms the heterogeneity of this disease and points to ethnic/racial origins as important factors when examining the HLA association. This is particularly pertinent as HLD-DR4 has been strongly linked to autoantibody formation in idiopathic dilated cardiomyopathy in Caucasians. The lack of any HLA antigen association in Omanis would argue against the proposed HLA-linked autoimmune pathology of idiopathic dilated cardiomyopathy.

Cardiomyopathy, Dilated↗
PubMed1995

HLA antigens in Omani patients with vitiligo.

Fifty native Omanis with vitiligo were studied to compare the incidence of HLA ABC and DR antigens with a control population. HLA Bw6 was found in 82% of patients compared with 49% controls (Pc = 0.0009 RR = 4.56) and HLA DR7 occurred in 40% of patients and 9% in controls (Pc = 0.00075 RR = 6.17). HLA DR7 was significantly increased in those patients with acrofacial, compared to focal disease (57% vs. 24% P = 0.038). Sixty-six per cent of the patients in this study had parents who were consanguineous and a positive family history was only found in this group with an incidence of 32%. HLA Bw4 segregated 100% with patients with a positive family history compared with 48% in consanguineous patients without a positive family history (Pc = 0.011 RR = 23). Vitiligo appears to be associated with different HLA antigens in different ethnic groups.

Female↗
PubMed1995

The binding of jacalin with rabbit immunoglobulin G.

Rabbit immunoglobulin G (IgG) was subjected to affinity chromatography on a column of jacalin-Sepharose 4B. While the majority of IgG molecules did not bind, a small fraction, representing about 25% of the total IgG applied, bound to jacalin-Sepharose 4B. The binding of rabbit IgG to jacalin was further evidenced by ELISA performed on jacalin coated microtitre plates. While the jacalin-retained IgG fraction displayed strong binding, the unretained fraction did not demonstrate any detectable binding. Upon SDS-PAGE, both the jacalin retained and unretained rabbit IgG fractions displayed identical protein profiles. Upon protein blotting it was demonstrated that jacalin binding sites were located only on the heavy chain of IgG. These results suggest that rabbit IgG molecules are heterogeneous with respect to their glycosylation patterns. A small fraction of rabbit IgG molecules binds jacalin and the process is probably mediated through O-linked oligosaccharides present on the heavy chain of IgG.

Animals↗
PubMed1995

Maturation of immunoglobulin-A binding proteins in the seeds of jackfruit.

The accumulation of proteins in the jackfruit seeds was monitored by extracting seeds proteins at various stages of growth. The early developing seed had several protein bands distributed over a molecular weight range of 10-67 kDa. But the mature seeds contained fewer bands with two of them being prominent at 12 and 15.4 kDa. Upon isoelectric focusing, the mature seed proteins were resolved into several bands distributed over a pH range of 4-9. While the mature seed proteins contained powerful hemagglutinating activities, these were not detected in the early developing seed. In contrast, the early developing seed had immunoglobulin A (IgA) binding activity as determined by enzyme-linked immunosorbent assay (ELISA). By Western blotting it was found that the early developing seed contained a novel 10 kDa IgA binding protein that was not present in the mature seeds.

Carrier Proteins↗
PubMed1993

Identification of a novel 4 kDa immunoglobulin-A-binding peptide obtained by the limited proteolysis of jacalin.

Jacalin, an IgA-binding lectin from jackfruit (Artocarpus heterophyllus) seeds, was isolated by the passage of PBS extracts of seeds over an affinity matrix containing IgA-Sepharose-4B. It was further purified by HPLC. When analyzed by SDS-PAGE under both reducing and nonreducing conditions, the native jacalin was dissociated into two subunits of 12 and 15.4 kDa. Both the subunits could bind IgA. Peptide mapping performed with radioiodinated jacalin indicated that both the subunits were susceptible to proteolysis by Staphylococcus aureus V8 proteinase. One degradation product was a small peptide of 4 kDa. This small proteolytic fragment also bound IgA. The amino-termini of the two major IgA binding subunits, 12 and 15.4 kDa, were identical. The 4 kDa IgA-binding proteolytic fragment of jacalin had a different amino-terminal sequence, suggesting that the region of jacalin which binds IgA does not remain close to the amino-terminus of the peptide.

Amino Acid Sequence↗
PubMed1992

A controlled trial of surgery for trachomatous trichiasis of the upper lid.

The effectiveness of commonly used procedures to correct trachomatous trichiasis of the upper lid was examined in a clinical trial in Oman. Lids were graded as having minor trichiasis (five or fewer lashes), major trichiasis (more than five lashes), and defective lid closure. Randomly allocated surgery specific for lid grade was completed in 384 lids, of which 369 (96%) were followed up once or twice approximately 9 and 21 months after surgery. The definition of operative success included no evidence of trichiasis and complete lid closure. Tarsal rotation was the most effective operation and was successful in 80% of cases of minor trichiasis, compared with success rates of 29% for electrolysis and 18% for cryoablation. Tarsal rotation was successful in 77% of cases of major trichiasis, compared with a 41% success rate for tarsal advance and rotation. Surgery for major trichiasis produced a significant improvement in visual acuity in operated vs nonoperated fellow eyes in a regression model incorporating the between-eyes correlation of visual acuity.

Cornea↗