Biomedical subjects

A Naeem

Publications and source records attributed to A Naeem.

At least 19 recordsLinked to original sources

PubMed2006

Experimental measurement of proton, Cd, Pb, Sr, and Zn adsorption onto the fungal species Saccharomyces cerevisiae.

Proton, Cd, Pb, Sr, and Zn adsorption onto the fungal species Saccharomyces cerevisiae were measured in bulk adsorption experiments as a function of time, pH, surface: metal ratio, and ionic strength, and we measured the electrophoretic mobility of the cells as a function of pH. We modeled the acid/base properties of the fungal cell wall by invoking a nonelectrostatic surface complexation model with four discrete surface organic acid functional group types, with average pKa values (with 1 sigma uncertainties) of 3.4 +/- 0.4, 5.0 +/- 0.2, 6.8 +/- 0.4, and 8.9 +/- 0.6. The affinity of the fungal cells for the metal ions follows the following trend: Pb > Zn > Cd > Sr. We used the metal adsorption data to determine site-specific stability constants for the important metal fungal surface complexes. Our results suggest that S. cerevisiae may represent a novel biosorbent for the removal of heavy metal cations from aqueous waste streams.

Adsorption↗

PubMed2006

Single step immobilized metal ion affinity precipitation/chromatography based procedures for purification of concanavalin A and Cajanus cajan mannose-specific lectin.

Concanavalin A and a mannose-specific lectin could be precipitated specifically from extracts of jack bean and Cajanus cajan seeds, respectively, using metal charged EGTA. Single step purification of the lectins was also possible using iminodiacetic acid-Sepharose charged with metal ions. Nondenaturing electrophoresis in polyacrylamide gel and that performed in presence of SDS ascertained homogeneity of the isolated lectins. The migration behavior of the purified lectins was comparable with those of the lectins purified using alternative procedures.

Cajanus↗

PubMed2005

Sorption of divalent metal ions on CrPO4.

The divalent metal ion sorption (Cu(2+), Cd(2+), Ni(2+), and Pb(2+)) on chromium phosphate (CrPO(4)) was studied as a function of pH, temperature, and concentration of metal ions. The sorption of metal ions is observed to increase with the increase in pH, temperature, and concentration of metal ions in solution. The mechanism of sorption is found to be the exchange of the hydrolyzed metal cations with the protons from solid at high temperature. The sorption at low temperature is found to be accompanied by the precipitation of the corresponding metal phosphates such as Pb(3)(PO(4))(2).

Adsorption↗

PubMed2005

Ion exchange sorption of Pb2+ ions on CrPO4.

The chromium(III) phosphate was observed to have a high affinity towards Pb2+ ion and the sorption capacities were found to be in the order: Pb2+ > Cu2+ > Cd2+ > Ni2+. Different characterization methods i.e. FTIR, SEM and EDX were employed to investigate the sorption mechanism of Pb2+ by chromium(III) phosphate, which showed that no new solid phases were present in the residue after sorption of Pb2+. The exchange between protons from the surface and Pb2+ from solutions was found to be responsible for Pb2+ sorption by chromium (III) phosphate.

Adsorption↗

PubMed2004

Temperature effect on xanthate sorption by chalcopyrite.

Xanthate ions sorption on copper ore (chalcopyrite) is studied as a function of temperature (273-293 K) in the pH range (8-11). The sorption of xanthate ions at all the pH values is observed to increase with the increase in temperature. The changes in pH, dissolution studies of the ore, SO2(4)- concentration determinations, and FTIR studies were employed to probe the mechanism of the process of adsorption. The results are found to fit successfully to the linear form of the Freundlich equation. The isosteric heats of adsorption (DeltaHi) are also calculated and show that the adsorption of xanthate on copper ore under the given experimental condition is endothermic in nature. The values of DeltaHi found are in conformity with the ion exchange sorption of xanthate by the chalcopyrite.

Adsorption↗

PubMed2004

Surface charge properties of Fe2O3 in aqueous and alcoholic mixed solvents.

Iron oxide (Fe2O3) was identified and characterized by surface area, X-ray diffractometry, and FTIR analyses. Surface charge densities, point of zero charge (PZC), and surface ionization constants were determined from the potentiometric titration data in various aqueous and aqueous organic mixed solvents in the temperature range 293-313 K. The surface charge densities were observed to decrease with the increase in temperature and concentration of metal ions in both the aqueous and aqueous organic mixed solvents. The absolute values of the surface charge density were found to change in the order aqueous > aqueous/methanol > aqueous/ethanol. Further, the PZC of the iron oxide was observed to shift to the higher pH values in the order ethanol > methanol > aqueous solution, which indicated a decrease in the acidity of the surface -OH groups. The pKa1 and pKa2 values of iron oxide were also determined and then used for determination of the surface potential (psi0) of the solid in aqueous and aqueous organic mixed solvents. The surface potential-surface charge curves generally supplemented the results derived from psi0-pH curves.

Journal Article↗

PubMed2004

Temperature effect on phosphate sorption by iron hydroxide.

The ion exchange sorption of phosphate on Fe(OH)3 is studied as a function of temperature (25-55 degrees C) and concentration (1.49-3.23 mmol l(-1)). The mechanism of sorption is observed to be the exchange of OH- anions from the adsorbent surface by those of H2PO4- and HPO4(2-) from the aqueous solution. An equation developed in the Langmuir formalism is used to explain the ion exchange sorption of phosphate on Fe(OH)3. The isosteric heat of sorption illustrates that the uptake of phosphate on Fe(OH)3 takes place through an anion exchange process, involving both the phosphate anions H2PO4- and HPO4(2-). Further, at higher temperature the solid prefers the HPO4(2-) anions forming a binuclear bridging complex.

Adsorption↗

PubMed2004

Phosphate/sulphate exchange studies on Amberlite IRA-400.

The sorption behaviour of phosphate on strong basic anion exchanger, Amberlite IRA-400 (SO4(2-) form) is studied as a function of pH (3-11) at two different initial concentration ranges (0.161 - 0.807 mmol l(-1), 3.874 - 6.134 mmol l(-1)) at 25 degrees C. The stiochiometry of the exchange reactions is observed to be dependent upon concentration and pH of the solutions. It is suggested that the sorption of phosphate takes place initially as PO4(3-) followed by HPO4(2-)/H2PO4(-). The data obtained is explained with the help of a modified Langmuir and mass law action equations.

Adsorption↗

PubMed2003

Selective removal of Pb2+ by AlPO4.

Aluminium(III) phosphate was observed to have a very high selectivity towards Pb2+ ions. Under similar conditions, the sorption capacities of the exchanger were observed to follow the order: Pb2+ > Zn2+ > Ni2+ > Co2+. The potentiometric titration data were used to determine the deprotonation constants (pKa) of AlPO4, which were dependent upon the temperature and nature of the metal cations present in the aqueous phase. Different physical methods i.e. FTIR, EPM and the wet chemical analyses were used to investigate the uptake mechanism of Pb2+ by the solid, which showed that no new solid phases were present in the solid residue after sorption of Pb2+ at pH 5. The exchange between protons from the surfaceand Pb2+ from solutions was found to be responsible for Pb2+ sorption by aluminum(III) phosphate.

Aluminum Compounds↗

PubMed2002

The sorption of divalent metal ions on AlPO4.

The sorption of Cu(2+), Pb(2+), Ni(2+), and Cd(2+) ions on the aluminum(III) phosphate was observed to increase with increases in the concentration, temperature, and pH of the system. The apparent dissociation (pK(a)), binding (pK(b)) and exchange (pK(ex)) constants of aluminum(III) phosphate were evaluated and found to be dependent upon the temperature and nature of the metal cations. The values of the dissociation constants (pK(a)) followed the order Pb(2+)<Cu(2+)<Cd(2+)<Ni(2+)<K(+), opposite to the values of the binding constants and selectivity shown by the solid. Ion exchange between protons from the surface and metal cations from aqueous solution was found to be responsible for the metal ions sorption by AlPO(4). The values of the dissociation (pK(a)) and exchange (pK(ex)) constants were used to estimate the corresponding apparent thermodynamic parameters (DeltaH(o)(diss), DeltaS(o)(diss) and DeltaH(o)(exch), DeltaS(o)(exch)). The values of DeltaH(o)(diss) and DeltaH(o)(exch) were found to be positive, which showed that both the dissociation and exchange processes were endothermic in nature. The DeltaS(o)(diss) and DeltaS(o)(exch) were also found to be positive, which showed that both the deprotonation and exchange processes on the AlPO(4) were entropy driven and spontaneous.

Adsorption↗

PubMed2002

Selective removal of chromates by macroporous exchanger Amberlyst A-21.

Sorption studies of chromate on weakly basic macroporous anion exchanger Amberlyst A-21 were performed as a function of pH (2 - 9), temperature (20 - 40 degrees C) and concentration (0.4 - 80 mmol.l(-1)). Chromate sorption was observed to decrease with the increase in initial pH of the solution, with a sorption maxima at pH 2 and increased with the increase in temperature. The changes in pH and in the ratio of choride ions released to chromate ions sorbed suggested that the anion exchange process was accomanied by hydrolysis and Donnan invasion. The FTIR spectra and isoeteric heat of sorption besides showing the hydrolysis / Donnan invasion of resin under different experimental conditions of concentration, pH and temperature also showed the dimerization of the chromate species inside the resin phase.

Adsorption↗

PubMed2001

Purification of Cajanus cajan root lectin and its interaction with rhizobial lipopolysaccharide as studied by different spectroscopic techniques.

A lectin present in roots of Cajanus cajan seedlings was isolated and purified by affinity chromatography. Sugar specificity assayed by hemagglutination-inhibition activity indicated that lectin belongs to glucose/mannose-specific group. The root lectin was found to be mannose-specific from the second day onwards as it was reconfirmed by specific elution of different days' sample from mannose agarose matrix. The maximum interaction of lectin with goat IgM was obtained in 10-day-old sample, indicating the highest crude lectin content. Lectin (total amount of eluted protein) from different days soil sample showed a maximum amount in 10-day-old sample. For further studies, the lectin has been isolated from the roots of 10-day C. cajan seedlings and purified on mannose-CL agarose column by affinity chromatography. Lectin was found to be a dimer of 18.5-kDa subunit as revealed by SDS-PAGE. Tryptophan quenching fluorescence was studied for C. cajan root lectin. Secondary structure of C. cajan root lectin as studied by circular dichroism was found to be a typical beta-pleated sheet structure. The interaction of purified root lectin with C. cajan-specific rhizobial lipopolysaccharide and its inhibition by specific and nonspecific sugars was demonstrated by fluorescence and circular dichroism. Results discussed in this paper were studied for the first time by different spectroscopic methods, suggesting that C. cajan root lectin-lipopolysaccharide interaction is specific.

Cell Wall↗

PubMed2001

Using costing as a district planning and management tool in Balochistan, Pakistan.

This paper reports on two studies in the province of Balochistan, Pakistan, analyzing the costs of primary care facilities and district and divisional hospitals. There are no known previous cost studies within Balochistan and the information gained is a critical element in developing a more rational allocation of resources within the health sector. The results demonstrate both the high level of under-funding of primary care within the health sector and the current inefficiency of allocation towards primary care and, within budgets, between different line items. Medicines in particular are significantly under-funded at the expense of staffing costs. The results are of use in developing more bottom-up budgeting systems within a more rational resource allocation system that is being developed as an element of the more decentralized health system towards which the province is working.

Budgets↗

PubMed2000

Mannose-binding lectin is a component of innate mucosal defense against Cryptosporidium parvum in AIDS.

BACKGROUND & AIMS: Nonimmune mechanisms of mucosal defense seem to be biologically important and might explain the observed variability in the course of enteric infection in immunodeficiency. Mannose-binding lectin (MBL) deficiency is associated with persistent diarrhea in children. We found that genetic determinants of MBL deficiency appear to predispose to cryptosporidiosis in patients with the acquired immunodeficiency syndrome (AIDS), and went on to study interactions of MBL and complement on Cryptosporidium parvum sporozoites. METHODS: This study involved cross-sectional study of MBL genotype and enteric infection in 72 Zambian AIDS patients with diarrhea, immunofluorescence analysis of MBL and C4 binding to C. parvum, and immunoblotting for MBL and complement in small intestinal fluid. RESULTS: Individuals homozygous for MBL structural gene mutations were at increased risk of cryptosporidiosis (odds ratio, 8.2; 95% confidence interval, 1. 5-42; P = 0.02). Lectin-mediated and concentration-dependent binding of purified MBL was detected on sporozoites but not oocysts, and MBL activated C4 on sporozoites. MBL, C3, C4, and albumin were detected in small intestinal fluid in half the patients tested, suggesting transudation of serum components into the enteropathic gut. CONCLUSIONS: The increased risk of cryptosporidiosis in MBL deficiency appears to include patients with AIDS. It may operate through MBL-mediated complement activation on sporozoites.

Acquired Immunodeficiency Syndrome↗

PubMed2000

The branchial arches and HGF are growth-promoting and chemoattractant for cranial motor axons.

During development, cranial motor neurons extend their axons along distinct pathways into the periphery. For example, branchiomotor axons extend dorsally to leave the hindbrain via large dorsal exit points. They then grow in association with sensory ganglia, to their targets, the muscles of the branchial arches. We have investigated the possibility that pathway tissues might secrete diffusible chemorepellents or chemoattractants that guide cranial motor axons, using co-cultures in collagen gels. We found that explants of dorsal neural tube or hindbrain roof plate chemorepelled cranial motor axons, while explants of cranial sensory ganglia were weakly chemoattractive. Explants of branchial arch mesenchyme were strongly growth-promoting and chemoattractive for cranial motor axons. Enhanced and oriented axon outgrowth was also elicited by beads loaded with Hepatocyte Growth Factor (HGF); antibodies to this protein largely blocked the outgrowth and orientation effects of the branchial arch on motor axons. HGF was expressed in the branchial arches, whilst Met, which encodes an HGF receptor, was expressed by subpopulations of cranial motor neurons. Mice with targetted disruptions of HGF or Met showed defects in the navigation of hypoglossal motor axons into the branchial region. Branchial arch tissue may thus act as a target-derived factor that guides motor axons during development. This influence is likely to be mediated partly by Hepatocyte Growth Factor, although a component of branchial arch-mediated growth promotion and chemoattraction was not blocked by anti-HGF antibodies.

Animals↗

PubMed2000

Resource allocation and budgetary mechanisms for decentralized health systems: experiences from Balochistan, Pakistan.

This paper identifies key political and technical issues involved in the development of an appropriate resource allocation and budgetary system for the public health sector, using experience gained in the Province of Balochistan, Pakistan. The resource allocation and budgetary system is a critical, yet often neglected, component of any decentralization policy. Current systems are often based on historical incrementalism that is neither efficient nor equitable. This article describes technical work carried out in Balochistan to develop a system of resource allocation and budgeting that is needs-based, in line with policies of decentralization, and implementable within existing technical constraints. However, the development of technical systems, while necessary, is not a sufficient condition for the implementation of a resource allocation and decentralized budgeting system. This is illustrated by analysing the constraints that have been encountered in the development of such a system in Balochistan.

Budgets↗

PubMed1999

Comparative Sorption Properties of Metal(III) Phosphates.

Sorptionbehavior of metal(III) phosphates toward Zn(2+) was investigated using different concentrations, pHs, and temperatures. Ion exchange between protons from the surface and metal cations from solutions was found to be responsible for metal sorption by metal(III) phosphates. Dissociation constants of metal(III) phosphates and binding constants of the Zn(2+) with metal(III) phosphates were determined using Henderson-Hasselbach and modified Langmuir equations, respectively. The sorption process in all the three metal phosphates was found to be endothermic in nature while the dissociation process was observed to be endothermic in AlPO(4) and FePO(4) and exothermic in CrPO(4). Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

Detection of anti-colon antibodies in inflammatory bowel disease using human cultured colonic cells.

BACKGROUND: Investigation of anti-colon antibodies may be simplified if a sensitive method and homogeneous source of antigen were available. AIMS: To examine the anti-colon antibody response using human colonic carcinoma cell lines as antigen. SUBJECTS: Patients with inflammatory bowel disease and other gastrointestinal disorders and healthy controls were studied. METHODS: Comparative enzyme linked immunosorbent assays (ELISAs) were performed to assess the value of whole Caco-2, HT-29, and LS-180 cells as antigen. The antigenic determinants of the immune response were characterised by western blot analysis. RESULTS: Sera demonstrated immunoreactivity against each of the cell lines, but different epitopes were recognised. Applying whole Caco-2 cells as antigen in an ELISA, the prevalence of anti-colon antibodies was significantly greater in patients with ulcerative colitis (36%) than Crohn's disease (13%), other gastrointestinal disorders (13%) and healthy controls (0) (p<0. 05). The immune response was not associated with one predominant antigen. CONCLUSIONS: Fixed whole cell ELISA is a simple and feasible method for studying the anti-colon antibody response. This response is non-specific, being directed against multiple antigens, and is likely to be an epiphenomenon of inflammatory bowel disease, more so for ulcerative colitis than Crohn's disease.

Adolescent↗