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Biomedical subjects

N Mohamed

Publications and source records attributed to N Mohamed.

At least 19 recordsLinked to original sources
PubMed2006

SYBR Green real-time reverse transcription-polymerase chain reaction assay for the generic detection of coronaviruses.

Coronaviruses are etiologic agents of respiratory and enteric diseases in humans and in animals. In this study, a one-step real-time reverse transcription-polymerase chain reaction (RT-PCR) assay based on SYBR Green chemistry and degenerate primers was developed for the generic detection of coronaviruses. The primers, designed in the open reading frame 1b, enabled the detection of 32 animal coronaviruses including strains of canine coronavirus, feline coronavirus, transmissible gastroenteritis virus (TGEV), bovine coronavirus (BCoV), murine hepatitis virus (MHV) and infectious bronchitis virus (IBV). A specific amplification was also observed with the human coronaviruses (HCoV) HCoV-NL63, HCoV-OC43, HCoV-229E and severe acute respiratory syndrome coronavirus (SARS-CoV). The real-time RT-PCR detected down to 10 cRNA copies from TGEV, BCoV, SARS-CoV and IBV. In addition, the assay exhibited a high sensitivity and specificity on clinical samples from different animal species. The developed assay represents a potential tool for laboratory diagnostics and for detecting still uncharacterized coronaviruses.

Animals↗
PubMed2005

A transgenic mouse model for studying the clearance of blood-borne pathogens via human complement receptor 1 (CR1).

Complement receptor 1 (CR1) on the surface of human erythrocytes facilitates intravascular clearance of complement-opsonized pathogens. The need for complement activation can be circumvented by directly coupling the organism to CR1 using a bispecific monoclonal antibody heteropolymer (HP). Lack of a functional homologue to CR1 on mouse erythrocytes has made it difficult to study HP-dependent clearance of pathogens in small animals. We have developed a transgenic mouse that expresses human CR1 on erythrocytes. CR1 antigen is of appropriate size and in a clustered distribution as confirmed by immunoblotting and fluorescence microscopy, respectively. HP that immobilized bacteriophage PhiX174 prototype pathogen to erythrocyte CR1 of the transgenic mice increased the rate of clearance of the virus compared with HP that bound bacteriophage, but not CR1. This transgenic mouse model will allow evaluation of different HPs for their in vivo efficacy and potential as human therapeutics.

Animals↗
PubMed2005

Schistosoma infection inhibits cellular immune responses to core HCV peptides.

Patients coinfected with hepatitis C virus (HCV) and the trematode, Schistosoma mansoni, have an increased incidence of viral persistence and accelerated fibrosis. To investigate immunological mechanisms responsible for this more aggressive natural history of HCV, the core HCV-specific T-cell responses were analysed in 44 donated blood units rejected because they had antibodies to HCV (anti-HCV). Half also had anti-S. mansoni antibodies, evidence of past or active infection. HCV-specific ELISPOT responses were examined using pools of 180 overlapping 9-mer peptides with offsets of one covering the core of HCV genotype 4a. Comparison of T-cell responses in blood units positive for both anti-HCV and anti-Schistosoma antibodies with blood units positive only for anti-HCV antibodies showed a significant decrease in core-specific T-cell IFN-gamma (505+/- 46 vs. 803 +/- 66 ISC/10(6) cells, P < 0.001), IL-4 (2 +/- 108 vs. 641 +/- 131 ISC/10(6) cells, P < 0.001), and IL-10 (159 +/- 105 vs. 466 +/- 407 ISC/10(6) cells, P < 0.002) responses. In contrast, there was no significant difference in cell-mediated immune response (CMI) to PHA mitogen between these two groups. Therefore, we concluded T cells from persons with anti-Schistosoma have reduced IFN-gamma, IL-4, and IL-10 secreting HCV-specific T-cell responses. This may explain why Schistosoma coinfection increases persistence and severity of HCV infection.

Animals↗
PubMed2003

The effect of heavy metals on nitrogen and oxygen demand removal in constructed wetlands.

The objective of this study is to investigate the respective effects of Zn, Pb and Cd as well as the combined effect of Zn, Pb, Cd and Cu on the removal of nitrogen and oxygen demand in constructed wetlands. Four laboratory-scale gravel-filled subsurface-flow constructed wetland units planted with cattails (Typha latifolia) were operated outdoors and fed with primary-treated domestic wastewater at a constant flow rate of 25 ml/min. After 6 months, three of the wetland units were fed with the same type of wastewater spiked with Zn(II), Pb(II) and Cd(II), respectively, at 20, 5 and 1 mg/l for a further 9 months. The remaining unit was fed with the same type of wastewater spiked with a combination of Zn(II), Pb(II), Cd(II) and Cu(II) at concentrations of 10, 2.5, 0.5 and 5 mg/l, respectively, over the same period. The chemical oxygen demand (COD) and ammoniacal nitrogen (AN) concentrations were monitored at the inlet, outlet and three additional locations along the length of the wetland units to assess the performance of the wetland units at various metal loadings. At the end of the study, all cattail plants were harvested for the determination of total Kjeldahl nitrogen and metal concentrations. The results showed that the COD removal efficiency was practically independent of increasing metal loading or a combination of metal loadings during the duration of the study. In contrast, the AN removal efficiency deteriorated progressively with increasing metal loading. The relative effect of the heavy metals was found to increase in the order: Zn<Pb<Cd and the synergistic effect of metals was not observed. The metals seem to exhibit some inhibitory effect on nitrogen uptake by cattail plants as indicated by lower nitrogen uptake rates in comparison to rates recorded in wetland systems treating domestic wastewater only.

Ecosystem↗
PubMed2003

Removal and speciation of heavy metals along the treatment path of wastewater in subsurface-flow constructed wetlands.

This study was conducted to: (1) evaluate the performance of constructed wetlands in removing Zn, Pb and Cd, respectively, and Zn, Pb, Cd and Cu in combination and (2) investigate the speciation patterns of the dissolved metals differentiated according to their detectability by anodic stripping voltammetry (ASV) and their lability towards Chelex resin along the treatment path of metal-containing wastewater in horizontal subsurface-flow constructed wetlands. Four laboratory scale wetland units planted with cattails (Typha latifolia) were operated outdoors for six months. Three of the units were, respectively, fed with primary-treated domestic wastewater spiked with Zn(II), Pb(II) and Cd(II) whilst the fourth was spiked with a combination of Zn(II), Pb(II), Cd(II) and Cu(II). The results demonstrate that a metal removal efficiency of over 99% was achievable for wetland units treating the metals singly or in combination provided the sorption capacity of the media was not exceeded. When treating the metals in combination, an antagonistic effect, more significantly for Pb and Cd, on the sorptive metal uptake by media was observed. Based on the metal speciation patterns, the wetland system seemed to be capable of maintaining the ASV-labile metal species at relatively low level (< 10%) before media exhaustion.

Biodegradation, Environmental↗
PubMed2000

Novel experimental study of receptor-mediated bacterial adhesion under the influence of fluid shear.

Dynamic adhesion of cells to surfaces is a vital step in a variety of biochemical and physiological phenomena. Bacterial adhesion is responsible not only for problems associated with biofouling and biofilm formation in the biochemical industry but also in the initiation of certain infectious diseases. In this study, we report the effect of critical parameters, such as receptor and ligand densities and shear rate, on receptor-mediated dynamic bacterial adhesion. Adhesion of a pathogenic strain of Staphylococcus aureus to immobilized collagen was studied. The receptor density on the cell surface was varied by harvesting cells at different growth times and was quantified using flow cytometry. Dynamic adhesion experiments were conducted over a range of physiologically relevant shear rates (50 to 1500 s(-1)) using a parallel-plate flow chamber. Video microscopy coupled with digital image processing was employed to quantify adhesion. A semiquantitative comparison between experimental results and theoretical data obtained using a previously proposed mathematical model was also performed. The results suggest that dynamic adhesion is dependent on receptor density and shear rate, but independent of ligand density. This report demonstrates the feasibility of using bacteria to study fundamental aspects of receptor-mediated dynamic adhesion.

Bacterial Adhesion↗
PubMed2000

Quantification of Staphylococcus aureus cell surface adhesins using flow cytometry.

The initiation of many infectious diseases involves specific adhesion of bacteria to host tissue proteins and carbohydrates. Staphylococcus aureus is known to bind specifically to several proteins in the extracellular matrix (ECM). We report the quantification of the collagen and fibronectin adhesin densities on the staphylococcal surface using flow cytometry. Our results are in agreement with previous reports on the transcription of the respective genes and demonstrate different patterns of temporal expression for the two adhesins in the strains studied. We demonstrate a convenient technique for quantification of bacterial adhesins that can be used in studies aimed at characterization of bacterial adhesion to ECM components and understanding expression of adhesins during the course of an infection.

Adhesins, Bacterial↗
PubMed1999

Inhibition of Staphylococcus aureus adherence to collagen under dynamic conditions.

Staphylococcus aureus is the most common etiological agent of bacterial arthritis and acute osteomyelitis and has been shown to bind to type II collagen under static and dynamic conditions. We have previously reported the effect of shear on the adhesion of S. aureus Phillips to collagen and found that this process is shear dependent (Z. Li, M. Höök, J. M. Patti, and J. M. Ross, Ann. Biomed. Eng. 24[Suppl. 1]:S-55). In this study, we used recombinant collagen adhesin fragments as well as polyclonal antibodies generated against adhesin fragments in attempts to inhibit bacterial adhesion. A parallel-plate flow chamber was used in a dynamic adhesion assay, and quantification of adhesion was accomplished by phase contrast video microscopy coupled with digital image processing. We report that both recombinant fragments studied, M19 and M55, and both polyclonal antibodies studied, alpha-M17 and alpha-M55, inhibit adhesion to varying degrees and that these processes are shear dependent. The M55 peptide and alpha-M55 cause much higher levels of inhibition than M19 and alpha-M17, respectively, at all wall shear rates studied. Our results demonstrate the importance of using a dynamic system in the assessment of inhibitory strategies and suggest the possible use of M55 and alpha-M55 in clinical applications to prevent infections caused by S. aureus adhesion to collagen.

Adhesins, Bacterial↗
PubMed1999

Functional analysis of the Staphylococcus aureus collagen adhesin B domain.

The Staphylococcus aureus collagen adhesin (CNA) occurs in at least four forms that differ in the number (one, two, three, or four) of B domains. The B domains contain 187 amino acids and are located between the domains that anchor CNA to the cell envelope and the ligand-binding A domain. To determine whether a B domain is required for functional expression of CNA, we cloned the 2B cna gene from S. aureus strain Phillips and then eliminated both B domains by overlapping PCR. The absence of a B domain did not affect processing of the collagen adhesin to the cell surface or the ability to bind collagen. Based on our recent demonstration that the capsule can mask CNA on the surface of S. aureus cells (A. F. Gillaspy et al., Infect. Immun. 66:3170-3178, 1998), we also investigated the possibility that multiple B domains can extend the ligand-binding A domain outward from the cell surface and thereby overcome the inhibitory effect of the capsule. Specifically, we cloned the naturally occurring 4B CNA variant from S. aureus UAMS-639 and, by successive elimination of B domains, generated 1, 2, and 3B variants that are isogenic with respect to the 4B clone. After introducing each variant into microencapsulated and heavily encapsulated strains of S. aureus and growing cells under conditions known to affect capsule production (e.g., growth on Columbia agar), we correlated capsule production with exposure of CNA on the cell surface and the ability to bind collagen. Under no circumstance was the masking effect of the capsule reduced by the presence of multiple B domains. These results indicate that the B domains do not extend the ligand-binding A domain outward in a fashion that can overcome the inhibition of collagen binding associated with capsule production.

Adhesins, Bacterial↗
PubMed1998

Severe thalassaemia intermedia: clinical problems in the absence of hypertransfusion.

In many of the parts of the world where thalassaemia is common, the blood supply is inadequate or unsafe, and desferrioxamine is too expensive for routine use. We classify some patients as having 'severe thalassaemia intermedia', i.e. those with moderately severe thalassaemia who can survive without regular transfusions, but who are at risk of many complications which are reviewed here. These include bone deformity and fractures, extramedullary haemopoietic tumours, leg ulcers, autoimmune haemolysis and, especially after splenectomy, thromboembolism and infection. An increase in the quality and safety of the blood supply, and a cheaper and/or oral iron chelator, would enable more of these patients to be treated as thalassaemia major and have improved survival and quality of life.

Blood Component Transfusion↗
PubMed1998

Gestational diabetes and subsequent development of NIDDM in aboriginal women of northwestern Ontario.

OBJECTIVES: To determine (1) the risk of development of non-insulin-dependent diabetes mellitus (NIDDM) in women with a previous history of gestational diabetes mellitus (GDM), (2) the average duration between diagnoses of GDM and NIDDM, (3) various modes of presentation, and (4) adequacy of follow-up post diagnosis of GDM. METHODS: A retrospective chart review of women diagnosed with GDM in the Sioux Lookout Zone between 1985-1995. There were 4,211 pregnancies and 332 women with a diagnosis of GDM. Sixty-one charts were randomly selected. Both GDM and NIDDM were defined according to World Health Organization standards. RESULTS: Seventy percent of the women with GDM went on to develop NIDDM. The average duration between diagnosis of GDM and diagnosis of NIDDM was three years. Greater than 70% of the women developed NIDDM within four years post diagnosis of GDM. The majority presented with asymptomatic hyperglycemia (88%); 3% presented with acidosis; 6% presented with symptoms of polydipsia and polyuria; and 3% presented with abnormal weight gain. Specific physician-requested follow-up after six weeks postpartum occurred in only 38% of the cases. However six-week follow-up occurred in 41%, a yearly follow-up occurred in 61% of the women, and 81% of the women had some sort of follow-up post diagnosis of GDM. CONCLUSIONS: The risk of developing NIDDM after GDM is very high in Aboriginal women of the Sioux Lookout Zone. There is an urgent need for a structured follow-up program for this group of high-risk women. Furthermore, the offspring of these pregnancies should be a focus for follow-up and preventive programs.

Adolescent↗
PubMed1997

Determination of 6,4'-bis-(2-imidazolinylhydrazone)-2-phenylimidazo[1,2-a]py ridine in plasma and whole blood by high-performance liquid chromatography.

A selective and sensitive HPLC assay for the quantitative determination of a new antifilarial drug, 6,4'-bis-(2-imidazolinylhydrazone)-2-phenylimidazo[1,2-a]pyr idine (CDR 101) is described. After extraction from plasma and blood, CDR 101 was analysed using a C18 Nucleosil ODS column (250x4.6 mm, 5 microm particle size) and mobile phase of acetonitrile-0.05 M ammonium acetate adjusted to pH 3.0, with UV detection at 318 nm. The mean recoveries of CDR 101 in plasma and blood over a concentration range of 25-500 ng/ml were 95.5+/-2.01% and 83.3+/-1.87%, respectively. The within-day and day-to-day coefficient of variations for plasma were 3.23-6.21% and 2.59-9.90%, respectively, those for blood were 2.59-5.92% and 2.89-6.82%, respectively. The minimum detectable concentration for CDR 101 was 1 ng/ml in plasma and 2.5 ng/ml in whole blood. This method was found to be suitable for clinical pharmacokinetic studies.

Animals↗
PubMed1996

Classification and reconstruction in revision acetabular arthroplasty with bone stock deficiency.

Revision acetabular surgery with bone stock loss is a difficult problem. Defects are classified into contained cavitary (Type-1) defects and noncontained defects (Type 2A and 2B) based on preoperative radiographs and intraoperative findings. Fifty-four hips with Type-1 defects were treated with morsellized allograft. The overall success rate was 90% at 6.78 year followup. Type-2 defects are reconstructed with structural grafts. Twenty-nine hips with Type-2A defects (the allograft supports <50% of the cup) were reviewed at 7.1 years' followup. The success rate was 90)%. In all but 1 case the allograft united to host bone. No resorption or minor resorption was seen in 26 of 29 hips with minor column structural grafts. Type-2B defects all had structural allografts that supported >50% of the cup. There were 33 hips in this group observed for an average of 7.1 years. The rerevision rate in this group was 45%. However, 7 of 15 hips were reconstructed without additional graft at rerevision. The only factor that was clinically significant for success in Type-2B defects was choice of acetabular component. In hips that received roof rings with cemented cups, the success rate was 100% (excluding 1 infection). The authors support the use of allograft bone in revision acetabular surgery. When structural grafts are required, every attempt should be made to achieve >50% support from host bone. If this is not possible, then a roof reinforcement ring with a cemented cup is the acetabular component of choice.

Acetabulum↗
PubMed1995

Home environment and asthma in Kenyan schoolchildren: a case-control study.

BACKGROUND: There is increasing evidence that environmental factors contribute to the development of asthma, so the relationship was studied between home environment factors and asthma among school children of varying socioeconomic backgrounds living in a developing country. METHODS: A case-control study was performed in participants of a prevalence survey which included 77 schoolchildren with asthma (defined by a history of wheeze, doctor diagnosis, or a decline in FEV1 of > or = 10% at five or 10 minutes after exercise) and 77 age and gender matched controls. Subjects were selected from 402 school children aged 9-11 years attending five primary schools in the city of Nairobi who participated in a prevalence survey of asthma. Visits were made to the homes of cases and controls and visual inspection of the home environment was made using a checklist. A questionnaire regarding supplemental salt intake, parental occupation, cooking fuels, and health of all children in the family was administered by an interviewer. RESULTS: In multivariate analysis the following factors were associated with asthma: damage caused by dampness in the child's sleeping area (adjusted odds ratio (OR) 4.9; 95% confidence interval (CI) 2.0 to 11.7), air pollution in the home (OR 2.5; 95% CI 2.0 to 6.4), presence of rugs or carpets in child's bedroom (OR 3.6; 95% CI 1.5 to 8.5). Children with asthma reported a supplemental mean daily salt intake of 817 mg compared with 483 mg in controls. CONCLUSIONS: Home environmental factors appear to be strongly associated with asthma in schoolchildren in a developing nation. These findings suggest a number of hypotheses for further studies.

Air Pollution, Indoor↗
PubMed1995

Compliance with antimalarial chemoprophylaxis and the subsequent development of malaria: a matched case-control study.

To determine if there is a difference in compliance with antimalarial chemoprophylaxis between febrile travelers with and without malaria, 157 patients with malaria, a history of fever, and recent travel to a malaria-endemic area were compared with 157 matched controls. Antimalarial prophylaxis had been taken by 48% of all patients. Chemoprophylaxis use was correlated with region and purpose of travel. Cases were less likely to have taken prophylaxis (53%) than controls (76%) (odds ratio = 0.35, confidence interval = 0.27, 0.73), even after controlling for region of travel, purpose of travel, and previous exposure to malaria. Chemoprophylaxis was effective in reducing malaria risk. Travel agents and health practitioners should provide all travelers to malaria-endemic areas with adequate information about chemoprophylaxis and its importance.

Adult↗