Search PubMed⌕ Search

Biomedical subjects

S S Asghar

Publications and source records attributed to S S Asghar.

11 recordsLinked to original sources
PubMed1992

Molecular heterogeneity of the fourth component of complement (C4) and its genes in vitiligo.

In view of evidence suggesting vitiligo is an autoimmune disease, we investigated whether vitiligo is associated with inherited deficiencies of the fourth (C4) and second (C2) component of complement and with certain human leukocyte antigens (HLA). Analysis of functional activities of C4 and C2 in sera of patients with vitiligo (n = 42) showed that 17% of them had a heterozygous C4 deficiency and 5% had a heterozygous C2 deficiency. In the normal control group (n = 30), 3% had a heterozygous C4 deficiency and none had a C2 deficiency. C4 typing by Western blot analysis showed the frequency of the C4A*Q0 allele in the vitiligo patient group to be close to normal. However, the frequency of one C4B*Q0 allele was three times higher, and that of two C4B*Q0 alleles five times higher in the vitiligo patient group than the reported frequencies in normal control groups. Southern blot analysis of Taq1 digests of DNA using C4 and 21-hydroxylase probes showed that two patients with two C4B*Q0 alleles had a deletion of a 21-OHA-C4B segment. In the other patients, having one or two C4B*Q0 alleles, these null alleles probably occurred due to a loss of C4 gene expression. HLA analysis did not show any allelic association of C4A*Q0 or C4B*Q0 with any HLA antigen in vitiligo, but confirmed the previous findings of a negative association with HLA-DR3 and a positive association with HLA-DR4. These results suggest that abnormalities of the C4B gene and the above-mentioned associations with HLA antigens may be some of the risk factors in vitiligo.

Adrenal Hyperplasia, Congenital↗
PubMed1992

CD59: a molecule involved in antigen presentation as well as downregulation of membrane attack complex.

CD59 is a recently discovered complement (C) regulatory protein. Three activities of CD59 have been recognized so far. It can downregulate the activation of the C cascade at membrane attack complex formation stage, it participates in T-cell rosette formation with erythrocytes and appears to be necessary for T-cell activation. CD59 is broadly distributed on cells of various organs and this is compatible with its function of protecting cells and tissues from incidentally activated autologous C. CD59 is encoded by a single gene residing on chromosome 11. The entire sequence of CD59 cDNA is known, from which the amino acid structure of CD59 has been deduced. Mature CD59 is made up of 103 amino acids. It has two potential N-glycosylation sites. Carbohydrate constitutes about 20% of the molecular mass of CD59. The protein part of the molecule is covalently linked to an oligosaccharide which, in turn, is glycosydically linked to phosphatidylinositol (PI). CD59 is anchored to the cells via PI moiety. The fine structure of the PI anchor of CD59 has not yet been established. Decreased expression of CD59 has been shown in two diseases. In paroxysmal nocturnal hemoglobinuria, erythrocytes (type III) lacking CD59 (and other PI proteins) have susceptibility to lysis by membrane attack complex. In psoriasis, expression of CD59 (and CD55) is drastically decreased in psoriatic lesions, presumably due to PI cleavage involving signal transduction mechanism(s) leading to increased proliferation of various cell types in lesional skin.

Amino Acid Sequence↗
PubMed1991

Hereditary deficiency of C5 in association with discoid lupus erythematosus.

A 29-year-old woman with discoid lupus erythematosus had undetectable classic pathway complement activity. Hypocomplementemia was due to selective deficiency of C5. One of her children was also deficient. To our knowledge this is the first documented case of an association between discoid lupus erythematosus and C5 deficiency.

Adult↗
PubMed1991

Effects of renal failure on complement C3d levels.

Elevated plasma concentrations of complement split product C3d have been reported to represent activation of the complement system. In the present study the effect of renal function on C3d concentrations was investigated in patients with various degrees of renal impairment, in patients with chronic renal failure and in CAPD patients. It appeared that elevated plasma C3d concentrations were present in patients with plasma creatinine concentrations in excess of 200 mumol/l regardless of the type of kidney disease. It is very likely that this can be attributed to renal handling (i.e. glomerular filtration, tubular reabsorption and renal catabolism) of C3d in a similar way as has been demonstrated for other low molecular weight proteins. The peritoneal permeability to C3d was slightly less than could be expected on the basis of its molecular weight without evidence of local production of C3d. Renal function should be taken into account in the interpretation of elevated plasma concentrations of C3d.

Complement Activation↗
PubMed1991

Suppression of vascular injury at the Arthus reaction site by a complement inhibitor, 5,5',5''-(1,3,6-naphthalene-triyl-tris[sulfonylimino])-tris (1,3-benzene disulfonic acid) hexasodium salt.

A novel polyanionic complement inhibitor 5,5,5''-(1,3,6-naphthalene-triyl-tris[sulfonylimino])-tris(1 ,3-benzene- disulfonic acid) hexasodium salt (compound IIb) was tested for its ability to suppress vascular injury at the site of the Arthus reaction (AR). In control animals in which AR was evoked without drug treatment, venules at AR sites ranged from normal (arbitrarily defined as stage I) to destroyed (stage V). Between these two ends of the spectrum were venules with an accumulation of cells and deposits of electron dense material (stage II), accumulations of cells and deposits and small endothelial gappings (stage III), and accumulations of cells and depositions which had spread into perivascular tissue and small gappings (stage IV). In animals treated with compound IIb, the AR stopped at stage III or IV depending on the dose, it never reached stage V. In other words compound IIb treatment resulted in protection of endothelium, basal lamina and other structures from the destruction which is characteristically observed in the AR. The effect of high doses of compound IIb was similar to that described before for suramin.

Animals↗
PubMed1976

Human plasma kallikreins and their inhibition by amidino compounds.

Human plasma kallikreins (EC 3.4.21.8) were purified as three distinct enzyme entities which hydrolyzed arginine esters and were active in releasing kinin from heated human plasma as measured by guinea pig ileum contraction bio-assay. The three enzymatically active fractions were termed as 19 S, 7 S-I and 7 S-II kallikreins. They represented purifications of 262- 2200- and 110-fold, respectively. These enzyme activities showed differences in physicochemical and biochemical properties as it appears from their elution profile on Sephadex G-200 and DEAE-cellulose columns, affinity for substrates and susceptibility of inhibition by various protease inhibitors such as trasylol and soya bean trypsin inhibitor. The data suggest that all these three enzyme preparations were most likely kallikreins. All these three enzymes (19 S, 7 S-I and 7 S-II) were inhibited by a series of amidino compounds competitively. Diamidines consisting of two amidinophenyl residues linked in para position by molecular bridge were comparatively stronger inhibitors of all of three enzymes than those linked in meta position and those having single ring structure. The possibility that some of these amidino compounds might prove to be useful for treatment of disease states where the kallikrein-kinin system plays a role, is discussed.

Amidines↗
PubMed1976

Some properties of proteolysis by polymorphonuclear leukocyte-granule extracts.

The extracts of granules of human polymorphonuclear leukocytes hydrolyzed a variety of proteins including human and bovine hemoglobin, human fibrinogen, human and bovine serum albumin, bovine elastin, and casein. The hydrolysis of all the proteins except fibrinogen and elastin was increased by addition of urea. Various inhibitors of trypsin, kallikrein, plasmin, Clr, Cls, and other proteolytic enzymes had no inhibitory effect. Slight inhibition was observed with polyanethol sulfonate and strong inhibition with normal human serum. Serum of patients with hereditary angioneurotic edema having no functional C1-esterase inhibitor was as effective in inhibiting the proteolysis as normal serum. The inhibitor was localized in 4S fractions of normal serum fractionated on Sephadex G-200. Fractionation of normal serum by ammonium sulfate precipitation, Sephadex G-200 filtration, and CM-Sephadex chromatography did not result in appearance of inhibitory activity in more than one protein peak, suggesting the possibility that only one inhibitor might be responsible. Since all fractions which contained the inhibitor of proteolysis also contained alpha1-antitrypsin, since sera of patients having low alpha1-antitrypsin levels contained less inhibitory activity, and since antibodies against alpha1-antitrypsin reversed the inhibition obtained from normal serum, the inhibition of proteolysis may be attributed to alpha1-antitrypsin.

Angioedema↗
PubMed1976

Diagnostic procedures in immunodermatology.

Most immunologic diseases are caused by the derailment of the humoral or cellular pathways of the immunologic defense system. This derailment results from numerous factors such as the inability of the patient to remove the pathogen; the consumption, defect, or deficiency in any component of these pathways, and the overproduction of any of the components. To diagnose these immunologic disorders one has to detect the pathogen and the reactions caused by it and to determine the cause of its nonclearance. The immunofluorescence techniques has been invaluable in detecting both the antigen that causes the disease and the reactions initiated by the antigen, such as the production of antibodies and the activation of the complement system. The immunoperoxidase technique has also been used for these purposes in certain instances. For detecting the circulating immune complexes which occur as intermediates in the chain of reactions initiated by the antigen, various physiochemical and biologic techniques have been used. However, none of these tests seems to be totally reliable for determining whether circulating immune complexes are present. The consumption of complement was detected by hemolytic estimations and radial immunodiffusion or rocket electrphoresis. These techniques were also useful in detecting the hereditary deficiencies in immunoglobulins and components of classical and alternative pathways of complement activation. Since these techniques cannot be used to estimate IgE, the radioallergosorbent test was used to measure such levels in the atopic patients. Cellular hypersensitivity was detected with skin tests together with methods which assess the ability of lymphocytes to produce mediators in response to antigen. Many of these mediator assays, however, are not suitable for this purpose. A satisfactory substitute appears to be to determine the factor in antigen-stimulated, lymphocyte culture supernatants which activates macrophages to take up radiolabeled colloidal gold or radiolabeled glucosamine. In contact allergic dermatitis, an increase in the IgD-bearing lymphocytes and granulocytes has also been correlated with cellular hypersensitivity. Lymphocytes and polymorphonuclear leukocytes coated with antibodies mainly directed against nuclear antigens of the basal layer cells of the noninvolved epidermis have invariably been encountered in psoriasis. The use of these findings for diagnostic purposes and for understanding the mechanisms of certain diseases is being explored.

Animals↗
PubMed1975

CLq precipitin in the sera of patients with allergic vasculitis (Gougerot-Ruiter Syndrome).

The sera from two well-documented cases of allergic vasculitis were examined for the presence of C1q precipitins. Both sera contained material capable of precipitating C1q in agarose gel. The material from one of the sera was partially purified using ammonium sulfate precipitation. Sephadex G-200 filtration, and DEAE-cellulose chromatography. Attempts to identify the nature of C1q precipitin were unsuccessful, but it resembled the high-molecular-weight precipitins of sera from patients with systemic lupus erythematosus. In a lesion, deposition of fibrinogen, immunoglobulins, and complement were noted mainly in the vessel walls. No correlation between immunoglobulin and complement deposition in the skin and the presence of C1q precipitins in the blood could be established.

Aged↗