Search PubMed⌕ Search

Biomedical subjects

H Ahmed

Publications and source records attributed to H Ahmed.

At least 73 records · Page 4Linked to original sources
PubMed1988

Wistaria sinensis agglutinin: purification, carbohydrate specificity, and characterisation of the combining site.

A 2-acetamido-2-deoxy-D-galactose-binding agglutinin from Wistaria sinensis seeds, purified by affinity chromatography on a 2-acetamido-2-deoxy-D-galactose-starch conjugate, was homogeneous as judged by poly(acrylamide) disc gel electrophoresis. It had a mol. wt. of 66,000 (gel filtration on Sephadex G-150); on electrophoresis on SDS-poly(acrylamide) gel in the presence of 2-mercaptoethanol, it dissociated into sub-units of mol. wt. 34,000, suggesting the agglutinin to be a dimer; and it was a glycoprotein containing 4.8% of carbohydrate. It agglutinated several vertebrate erythrocytes, including human regardless of the blood group. In hapten-inhibition assays, 2-acetamido-2-deoxy-D-galactose and its glycosides were found to be better inhibitors than D-galactose and its glycosides, but N-acetyl-lactosamine was the most potent inhibitor. The binding involved HO-3,4 of the haptens and HO-2 partially.

Animals↗
PubMed1988

Phosphorylation in situ of atrial natriuretic peptide prohormone at the cyclic AMP-dependent site.

Previously we have shown that atrial natriuretic peptides (ANP) are phosphorylated at Ser-104 by cyclic AMP-dependent protein kinase (Rittenhouse, J. Moberly, L., O'Donnell, M.E., Owen, N.E., and Marcus, F. (1986) J. Biol. Chem. 261, 7607-7610). In our present study, atrial natriuretic peptide prohormone (pro-ANP) purified from extracts of rat atria that had been incubated in situ with [32P]orthophosphate was found to be phosphorylated. The site of in situ phosphorylation was localized to the ANP region of the prohormone and was further delineated to a chymotryptic peptide having the same retention time by high performance liquid chromatography as the hexapeptide Arg101-Arg102-Ser103-Ser(P)104-Cys105-Phe106+ ++. This hexapeptide was also formed from in vitro phosphorylated pro-ANP and synthetic ANP. It is thus likely that Ser-104 is the site of phosphorylation of pro-ANP both in situ and in vitro. Incubation of atria with intracellular cyclic AMP-elevating agents consistently increased the specific radioactivity of the resulting purified pro-ANP by 5-10-fold. However, the overall extent of phosphorylation was low, suggesting that a subpopulation of pro-ANP molecules are phosphorylated at Ser-104 by a cyclic AMP-mediated pathway.

Amino Acid Sequence↗
PubMed1987

Hemagglutination patterns of Pseudomonas aeruginosa strains of different serogroups, Habs and Fisher types.

Pseudomonas aeruginosa strains of sixteen Habs and three Fisher types were examined for their hemagglutination activity using vertebrate erythrocytes including human ones. Their carbohydrate-binding specificity as determined by hemagglutination-inhibition suggests a possible method of their purification. This study also indicates the possibility of an occurrence of multiple lectins of different specificity.

Hemagglutination Inhibition Tests↗
PubMed1986

Inactivation of thymidylate synthase by chlorine disinfectants.

The effects of two chlorine disinfectants, calcium hypochlorite (HTH) and 3-chloro-4,4-dimethyl-2-oxazolidinone (Agent I), on the activity of thymidylate synthase have been investigated. Although both disinfectants inactivated the enzyme, the following differences were observed: When the two disinfectants were used at the same total chlorine concentration, the rate and extent of inactivation were greater with Agent I than HTH. The substrate dUMP partially protected thymidylate synthase from inactivation by Agent I, but it did not appreciably protect against inactivation by HTH. Large changes in the ultraviolet spectrum of the enzyme occurred when it was treated with HTH, which suggests reactions with aromatic amino acid side chains; no spectral changes occurred when thymidylate synthase was treated with Agent I. Blocking the sulfhydryl groups of thymidylate synthase with sulfhydryl reagents prevented the irreversible inactivation of the enzyme by Agent I, but not by HTH.

Calcium↗
PubMed1986

Serological characterization of humoral lectin from Heterometrus granulomanus scorpion hemolymph.

A lectin in the hemolymph of Indian scorpion Heterometrus granulomanus was detected by agglutination of human and animal erythrocytes. The agglutinating activity was enhanced in presence of Ca2+ ion. The lectin shows specificity for sialic acid like many other sialic acid-specific lectins such as "Limulin", as the agglutination of erythrocytes was completely abolished by treatment with Vibrio cholerae neuraminidase. However, neuraminidase-treated rat and mouse erythrocytes exhibited high titers. This result was substantiated by crossed-absorption test which suggests the adjunct specificity of the Heterometrus lectin for these cells. Hemagglutination-inhibition results of the lectin indicate that sialic acid including its derivatives and sialoglycoconjugates are the inhibitors among which glycophorin was most potent.

Animals↗
PubMed1986

Purification of a sialic acid-specific lectin from the Indian scorpion Heterometrus granulomanus.

A sialic acid-specific lectin, scorpin, has been purified to apparent homogeneity from the Indian scorpion Heterometrus granulomanus by affinity chromatography on equine submandibular gland glycopeptides linked to Sepharose and gel filtration on Sephadex G-200. The lectin has a molecular mass of 500 000 Da and was dissociated into single polypeptide chains of 15 000 Da, as determined by SDS gel electrophoresis in the presence of 2-mercaptoethanol. Scorpin is a glycoprotein containing 2.8% sugars. Its specificity was investigated by the inhibition of hemagglutination with various derivatives of sialic acid and other sugars. N-Acetylneuraminic acid gave better inhibition than N-glycoloylneuraminic acid but showed less inhibitory effect than sialyl-alpha(2----3)-lactose and disialyllactose. Among the sialoglycoconjugates tested, equine submandibular gland glycopeptide was found to be the most potent inhibitor. Scorpin showed a strong tendency to bind to carboxyl groups, since reduction of the carboxyl group of N-acetylneuraminic acid destroyed the inhibitory potency of this sugar. Furthermore, D-glucuronic acid inhibited hemagglutination whereas N-acetylglucosamine or N-acetylgalactosamine were not inhibitors.

Animals↗
PubMed1985

Jackfruit (Artocarpus integrifolia) and the Agaricus mushroom lectin fit also to the so-called peanut receptor.

The lectin from jackfruit (Artocarpus integrifolia) reacts with the peanut-specific lectin receptor represented by the T-disaccharide, which is also part of the Thomsen (= T)-Friedenreich antigen, namely O-beta-D-galactosyl-(1----3)-N-acetyl-D-galactosamine. The difference between the jackfruit lectin and peanut lectin has been shown to be mainly due to the further linkage of the T-disaccharide: Whereas the peanut lectin reacts with both anomeric forms, jackfruit lectin and the closely - with respect to its specificity - related Agaricus bisporus mushroom lectin react predominantly with the alpha-linked T-disaccharide, so that they cannot detect the lipid-linked T-disaccharide, as the peanut lectin does.

Antigens, Tumor-Associated, Carbohydrate↗
PubMedDate not supplied

C-type lectins and galectins mediate innate and adaptive immune functions: their roles in the complement activation pathway.

In recent years, a 'new' pathway for complement activation mediated by the mannose-binding lectin (MBL) has been described as a key mechanism for the mammalian acute phase response to infection. This complement activation pathway is initiated by a non-self recognition step: the binding of a humoral C-type lectin [mannose-binding lectin (MBL)] to microbial surfaces bearing 'foreign' carbohydrate determinants. The recognition factor, MBL, is associated with a serine protease [MBL-associated serine protease (MASP)] which, upon MBL binding to the microbial ligand, activates the complement component C3, leading to either (a) phagocytosis of the opsonized target via the complement receptor, or (b) humoral cell killing via assembly of the membrane attack complex. Galectins (formerly known as S-type lectins) modulate activity of the complement receptor 3 (CR3), the macrophage membrane receptor for complement components C3b and iC3b, downstream products of the MBL pathway which are covalently bound to 'target cells. Galectins also mediate macrophage- and dendrocyte-adhesion to lymphocytes activated by signaling through another C-type lectin, the L-selectin, leading to immunoglobulin-mediated responses. Thus, the functional interplay of MBL, galectins and L-selectin in the acute phase response neutralizes the microbial challenge, and lead to further adaptive immunity. Although the observation of various components of the lectin pathway in different invertebrate species demonstrates the high conservation and ancient roots of the components of innate immunity, there has previously been no evidence supporting the possibility that the integral lectin-mediated complement activation pathway is present in invertebrates. We now have evidence for the coexistence of homologs of all the pathway's key components (MBL, MASP, C3, and galectin) in the protochordate Clavelina picta, suggesting the lectin-mediated pathway of complement activation preceded the immunoglobulin pathway in evolution. Therefore, despite being 'new' to the textbooks, experimental evidence indicates that this pathway is ancient, and has been conserved intact throughout its evolution.

Amino Acid Sequence↗
PubMedDate not supplied

An unusual association of a rare variant of Friedreich's ataxia with type-I neurofibromatosis in a Nigerian Fulani family: a 5-year follow-up study.

A very rare form of heredofamilial spinocerebellar degenerative disorder is reported in a 12-year old boy and his 39-year old Fulani mother. The two cases were compatible with the clinical picture of Harding's variant of spastic ataxia of childhood--a clinical and genetic entity distinct from the more common Friedreich's ataxia. The mode of progression of the disease and the computed tomographic (CT) and electrophysiologic findings in both patients also support the diagnosis. In addition, the mother had the typical clinical picture of type-1 neurofibromatosis combined with the rare heredofamilial ataxic syndrome. The signs of neurofibromatosis could not be detected in her child. The cases were followed up regularly for 5 years with the aim of identifying possible complications. These cases are reported because of the extreme rarity of Harding's variant of heredofamilial ataxia and the rarity of the association of this disorder with type-1 neurofibromatosis.

Adult↗