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Biomedical subjects

B Said

Publications and source records attributed to B Said.

At least 19 recordsLinked to original sources
PubMed2006

Culture of Helicobacter pylori from domestic water samples--the impact of strain variation on growth on solid and in liquid media.

Helicobacter pylori is an important global human pathogen and there is growing evidence from PCR assays that contaminated drinking water might be a possible source of infection in some circumstances. There are no validated protocols for direct isolation but various culture media have been developed for possible environmental sampling. Our aim here was to investigate how inter-strain variation might affect the interpretation of results with such media. Two laboratory adapted reference strains and four recent clinical isolates were tested on four solid media and in ten liquid media. Considerable variation was found between strains in their ability to recover on the different media after stress exposure (suspension in sterile tap water). Generally, clinical isolates were less robust than the laboratory-adapted strains and, overall, the former required longer recovery times. Our findings highlighted the importance of using a range of isolates for evaluations, as examination of laboratory-adapted strains alone did not provide an accurate representation of the utility of media that may be used to recover H. pylori from water.

Culture Media↗
PubMed2004

Detection of Helicobacter pylori by PCR but not culture in water and biofilm samples from drinking water distribution systems in England.

AIMS: To investigate treated water distribution systems in England as a source of Helicobacter pylori. METHODS AND RESULTS: Water and biofilms were obtained from 11 domestic and seven educational properties and from hydrants, reservoirs and water meters supplied by three water utilities. Samples were cultured on nonselective and antibiotic containing media combined with immunomagnetic separation concentration. Viable helicobacters were not detected in any of the 151 samples but Helicobacter-specific PCR assays detected DNA in 26% of samples from domestic properties, schools and hydrants with the highest frequency in biofilms (42%). Direct sequencing of six selected amplicons confirmed >95% sequence homology to H. pylori. CONCLUSIONS: While viable helicobacters were not isolated, evidence was obtained for the presence of Helicobacter DNA, including that of H. pylori. Biofilms on surfaces within water distribution systems may act either as sites for the passive accumulation of helicobacters or as potentially important reservoirs of infection. SIGNIFICANCE AND IMPACT OF THE STUDY: Our findings strengthen evidence that H. pylori may be transmitted through drinking water. However, there is currently no evidence that viable cells can survive the disinfection levels used in UK mains supplies and the health risk from this source remains unclear.

Base Sequence↗
PubMed2003

Outbreaks of infectious disease associated with private drinking water supplies in England and Wales 1970-2000.

In England and Wales over the last 30 years there have been 25 reported outbreaks of infection, associated with private water supplies (PWS). The majority (16 outbreaks) were reported after the introduction of enhanced surveillance. Although PWS only serve 0.5% of the population, 36% of drinking water outbreaks are associated with PWS. The main pathogen, campylobacter, was implicated in 13 (52%) outbreaks. Most reported outbreaks (88%) occurred in commercial or Category Two supplies, which potentially affect larger populations. The main factors implicated in these outbreaks are temporary or transient populations, treatment (lack or failure), the presence of animals and heavy rains. The public health problem associated with PWS could be prevented by the identification and understanding of risk factors, by the proper protection of water sources and adequate treatment and maintenance. This could be facilitated through the introduction of a risk assessment as part of a scheme for PWS.

Communicable Disease Control↗
PubMed2001

Synergism between cocaine and atropine at the caudal ventrolateral medulla of cats.

We have previously reported that the anticholinergic properties of cocaine may be important in cocaine induced apneusis. We have studied the effects of the cholinergic muscarinic antagonist atropine (ATR) on cocaine induced apneusis at the caudal chemosensitive areas of the ventrolateral medulla oblongata (CVLM). Experiments were performed in urethane anesthetized and tracheotomized cats with the CVLM surgically exposed. Topical application of ATR (44 mM ) to the CVLM produced significant decrements in minute ventilation (V(E)) and mean arterial blood pressure (MABP) (P<0.05) but the effects on tidal volume (V(T)), respiratory frequency (f) and heart rate (HR) were not significant. Administration of cocaine (37 mM) to ATR pretreated animals increased the incidence of cocaine induced respiratory arrest to more than twofold greater than when cocaine was administered in the absence of pretreatment. The ATR pretreated animals that did not experience inspiratory arrest after cocaine were shown to exhibit significant decrements in f and V(E) as a consequence of prolonged inspiratory pauses. The reduction in MABP after cocaine in ATR pretreated animals was also significant. These results suggest that ATR enhances the central respiratory toxicity of cocaine by acting synergistically at CVLM chemosensitive sites.

Animals↗
PubMed2001

Purification of follicular regulatory protein: possible plasminogen identity.

A partially purified protein (the SR fraction) of porcine and human origin has been extensively characterized as Follicular Regulatory Protein (FRP). In the current study, 1A8D5, one of several monoclonal antibodies raised against FRP, was used to further purify the protein. The monoclonal antibody cross-reacted only with porcine plasminogen, a key fibrinolytic proenzyme. A commercial polyclonal antibody for human plasminogen confirmed the relationship between plasminogen and bands of the SR fraction of the porcine follicular fluid. Sequencing of the N-terminal amino acids (54 kd) of the SR fraction indicated that it shared 100% identity with the short form of porcine plasminogen chain A and 93% identity to human plasminogen. Moreover, we demonstrated that this purified protein from human follicular fluid inhibited aromatase activity of granulosa cells, a key biological property of FRP. Given that plasminogen possesses most of the proposed properties of the protein termed FRP, we conclude that FRP is likely plasminogen itself or a plasminogen-related protein and not a novel protein.

Amino Acid Sequence↗
PubMed2000

Somatosensory evoked potential, neurological examination and magnetic resonance imaging for assessment of cervical spinal cord decompression.

The present study was designed to determine the relationship between neurological testing, anatomical imaging, and electrophysiological monitoring for assessing outcome of cervical spinal cord decompression. We prospectively studied 28 consecutive patients (age 39-76 yr) who were subjected to presurgical-(1-3 wk) and postsurgical (3-4 mo) neurological examination and recording of the median nerve somatosensory evoked potential (SEP). In 13 patients, magnetic resonance imaging (MRI) was also performed. Changes in neurological function, SEP and MRI were evaluated and graded as (1) improvement,(2) no change or (3) deterioration. Neurological outcome (NO) was based on changes in motor grade strength, sensory, reflexes and gait. The SEP outcome was based on changes in latency and disappearance of SEP waveform components whereas MRI evaluation was based on changes in spinal cord and canal diameters. Significance of association between NO, SEP and MRI was determined by Pearson's Chi-Square statistic (P<.05). The SEP improved in 71% (20/28) and deteriorated in 28% (8/28) of the subjects. An association between SEP changes and NO was found in 82% (23/28) of the subjects (P = .0038). Decompression increased the spinal canal diameter in 92% (12/13), and the spinal cord diameter in 38% (5/13) of the subjects. An association between NO, or SEP and MRI was not detected. Changes in median nerve SEP latency appear to be predictive of the neurological status of patients subjected to cervical spinal cord decompression. Postoperative increments in SEP latency or disappearance of the SEP waves were indicative of poor outcome after surgical decompression of the cervical spinal cord.

Adult↗
PubMed2000

Ferumoxide-enhanced MRI in patients with colorectal cancer and rising CEA: surgical correlation in early recurrence.

The purpose of this study was to evaluate the value of Ferumoxide-enhanced magnetic resonance (MR) imaging in the detection of hepatic metastases in high-risk patients treated for colorectal cancer that have rising CEA. We used 19 patients treated previously for colorectal cancer with rising CEA levels underwent an unenhanced T(1)-weighted (T1W), T(2)-weighted (T2W), STIR, and Ferumoxide-enhanced hepatic MRI. Following these studies, a laparotomy was performed and the liver was evaluated by palpation and intraoperative ultrasound. Two observers who were blinded to surgical results evaluated each MR sequence separately. The number of lesions considered highly suspicious for metastatic lesions were determined for each sequence and were compared to the results of surgery. The McNemar test was used to compare the outcomes of the different sequences. MR Imaging was unable to detect small (<5 mm) metastases discovered at surgery. The best non-contrast sequences for detecting metastases were the STIR with 42% sensitivity, 83% specificity and an overall accuracy of 56% and the T1W sequence (sensitivity 38%, specificity 100%, accuracy 57%), which were not significantly different (p 0.4). The noncontrast T2W sequence had a sensitivity of 29% and a specificity of 77% with an overall accuracy of 46%. When all pre contrast scans were grouped together the common sensitivity was 42%, specificity was 77% and accuracy was 54%. The post-ferumoxide T(2)W scans had a sensitivity of 42%, specificity of 85%, and accuracy of 57%, but did not detect any additional lesions. There was no statistical difference between the pre- and post-contrast studies with regard to identifying patients with metastatic disease (p 0.1). In conclusion, we found small hepatic metastases in patients with early signs of recurrent colorectal cancer are difficult to detect on MRI. Ferumoxide-enhanced MRI was unable to detect additional hepatic metastases and performed no better than unenhanced MRI in detecting small hepatic metastasis.

Adult↗
PubMed2000

DNA-damaging effects of genotoxins in mixture: modulation of covalent binding to DNA.

Modulation of DNA adduct formation by pre-existing adducts was examined in synthetic oligonucleotides and genomic DNA (calf thymus); genotoxins studied were N-acetoxy-acetylaminofluorene (N-AcO-AAF), aminofluorene (AF), aflatoxin B1-8,9-epoxide (AFB1-8,9-epoxide), and dimethylsulfate (DMS). Oligodeoxynucleotides containing either guanine-C8-AAF (Gua-C8-AAF) or Gua-C8-AF adducts and a neighboring unadducted guanine (G) (target G), located 1, 2, or 4 nucleotides from the adduct, were reacted, as single- (ss) or double-stranded (ds) substrates, with dimethylsulfate (DMS) or AFB1-8,9-epoxide. A modified Maxam-Gilbert technique showed that the presence of the AAF adduct lowered the extent to which AFB1-8,9-epoxide, but not DMS, reacted with target G. Binding of AFB1-8,9-epoxide to the target G was attenuated (> or =5-fold) when the target was located immediately adjacent to an AAF, but not AF, adduct in ds-DNA. Reaction with AFB1-8,9-epoxide increased when the target G was located 2 or 4 nucleotides from the AAF adduct. Pretreatment of calf thymus DNA with AAF (0-1.8% nucleotides modified) reduced levels of Gua-N7-AFB1 adducts formed after subsequent treatment with AFB1-8,9-epoxide. Pretreatment of calf thymus DNA with AFB1 did not alter levels of adducts formed after subsequent treatment with N-AcO-AAF. The supposition that aflatoxin B1-binding to DNA may be altered by conformational changes in the helix, due to the presence of a pre-existing AAF adduct, is supported by the absence of an effect by AF and confirmation of local denaturation of the oligomer helix by use of chemical probes hydroxylamine and diethylpyrocarbonate. Nonetheless, the importance of changes in the nucleophilicity of neighboring nucleotides and local steric effects cannot be ruled out.

2-Acetylaminofluorene↗
PubMed1999

Mutagenic activity and DNA adduct formation by 1, 2-epoxy-3-(p-nitrophenoxy)propane, an HIV-1 protease inhibitor and GST substrate.

Acid protease inhibitor 1,2-epoxy-3-(p-nitrophenoxy)propane (ENPP) is commonly used in research as a substrate for glutathione-S-transferase activity (GST) and recently was found to inhibit human immunodeficiency virus 1 (HIV-1) protease. The question of DNA-adduct formation and mutagenicity was investigated and found that ENPP causes DNA damage and acts directly to induce mutagenicity in Salmonella. Using HPLC analysis, ENPP was shown to bind covalently to guanine residues. The Salmonella mutagenicity assay indicated that ENPP enhanced the mutation frequencies in the base-substitution strain TA00 by more than 20 times above the background. Its mutagenic potency was comparable to that of well-known carcinogens, N-methyl-N-nitrosourea (MNU) and aflatoxin B(1)-8,9-epoxide (AFB(1)-8,9-epoxide). The results suggest that ENPP should be classified as a mutagenic compound and a potential carcinogen.

Carcinogens↗
PubMed1999

5-Methylcytosine in CpG sites and the reactivity of nearest neighboring guanines toward the carcinogen aflatoxin B1-8,9-epoxide.

The reactivity of guanines in an oligonucleotide containing mutational hot spots within the p53 gene (codons 248 and 249), 5'-CCG1G2AG3G4CCCA-3', toward dimethyl sulfate (DMS) and aflatoxin B1-8,9-epoxide (AFB1-8,9-epoxide) was investigated by a modified Maxam-Gilbert technique. 5-Methylcytosine in the CpG site of codon 248 did not appear to modulate the reactivity of target guanines G1, G2, G3, and G4 toward either genotoxin when compared to the sequence containing a nonmethylated CpG site. A similar experiment was conducted in which a 0.5-kb fragment of the human HPRT gene containing exon 1 and several CpG sites was treated with UV-activated aflatoxin B1. Results showed that guanine adduct formation was independent of the methylation status of the CpG site. These findings are discussed in relation to other studies that have shown that cytosine methylation has an inhibiting effect, an enhancing effect, or no effect on adduct formation with nearby guanine nucleotides.

5-Methylcytosine↗
PubMed1999

DNA-damaging effects of genotoxins in mixture: nonadditive effects of aflatoxin B1 and N-acetylaminofluorene on their mutagenicity in Salmonella typhimurium.

Most animal genotoxicity studies have used exposures to single chemicals; humans, however, are potentially exposed to mixtures of genotoxins. Cancer and developmental toxicity risks associated with genotoxins in mixture are generally estimated by assuming additivity of the components. Two or more genotoxins acting sequentially or simultaneously may present a greater or lesser hazard than that predicted by simple addition of their potencies. Previously, we studied the effect of one genotoxin on the binding of a second genotoxin to DNA in an in vitro system and demonstrated that consecutive binding of the two toxins was not additive. In the present study, the effect of one genotoxin on the mutagenicity of another was evaluated for two well-known genotoxins using the Salmonella assay. Pretreatment of frameshift strains TA98 and TA1538 with AFB1-8,9-epoxide (17.3 ng/plate) enhanced the mutagenicity induced by subsequent exposure to N-acetoxy-acetylaminofluorene (N-AcO-AAF) approximately 2-3 times above theoretical values for additivity. Pretreatment of base-substitution strain TA100 with N-AcO-AAF (0.1 microg/plate) inhibited the mutagenicity following subsequent exposure to AFB1-8,9-epoxide by 3 times below the theoretical additive value. Concentration-response relationships for these enhancing or inhibitory effects were demonstrated using increasing concentrations of the first genotoxin during pretreatment. These results demonstrate effects, other than additive, of sequential exposures to two genotoxins on the induction of mutations in a bacterial system.

2-Acetylaminofluorene↗
PubMed1998

Human lymphocyte heme oxygenase 1 as a response biomarker to inorganic arsenic.

We propose the use of human lymphocyte heme oxygenase 1 (HO1) as a biomarker of response to environmental arsenic exposure. We report the induction of HO1 in human lymphoblastoid cells (LBs) by arsenite in a dose-related manner. HO1 was identified by SDS-PAGE from its molecular weight and from its detection by Western blotting with anti-HO1. HO1 levels in LBs treated with arsenite increased by de novo synthesis as demonstrated by incorporation of 35S-methionine and by inhibition of HO1 synthesis by actinomycin D. The amount of HO1 in LBs was estimated by quantifying Western blots. HO1 was also induced by 10 microM cadmium or mercuric chloride. We suggest that circulating lymphocyte HO1 levels may be useful in assessing the biological activity of arsenic exposure in vivo under properly controlled conditions of simultaneous urinalysis for arsenic, cadmium, and mercury.

Arsenic↗
PubMed1996

Use of gene probes and adhesion tests to characterise Escherichia coli belonging to enteropathogenic serogroups isolated in the United Kingdom.

Nine hundred and twenty-five Escherichia coli isolates from cases of diarrhoea in the United Kingdom and belonging to enteropathogenic E. coli (EPEC) O serogroups were examined for virulence properties. The tests included adhesion to HEp-2 cells, the fluorescence actin staining (FAS) test (which correlates with the ability to cause attaching and effacing lesions) and DNA hybridisations with probes to detect sequences for eaeA (E. coli attaching and effacing factor), EAF (EPEC adherence factor), verocytotoxins VT1 and VT2, enteroaggregative E. coli and diffusely adherent E. coli. The O serogroups examined were 18, 26, 44, 55, 86, 111, 114, 119, 125, 126, 127, 128 and 142. Six hundred and sixty strains (71.4%) hybridised with at least one of the DNA probes. Over 80% of strains in O serogroups 26, 55, 119, 125, 127 and 142 and 41% of strains of serogroups 86, 111, 114, 126 and 128 hybridised with the eae probe and most showed localised attachment and were FAS-positive. However, <10% of these eae probe-positive strains hybridised with the EAF probe. Eighty-four of 232 strains in O serogroups 44, 86, 111, and 126 were enteroaggregative. VT genes were detected in 57 of 402 strains in O serogroups 26, 55, 111 and 128. Identification of EPEC by serogrouping was shown to be an effective method of identifying strains with pathogenic potential, although the organisms were diverse in their properties.

Bacterial Adhesion↗
PubMed1995

Detection and differentiation of the gene for toxin co-regulated pili (tcpA) in Vibrio cholerae non-O1 using the polymerase chain reaction.

The polymerase chain reaction has been used to differentiate the gene which encodes the toxin co-regulated pili (tcpA) of the El Tor and classical biotypes of Vibrio cholerae O1. The same PCR primers were applied to strains belonging to non-O1 serogroups that produced cholera toxin. The size of fragment amplified was either identical to the tcpA of biotype El Tor (471 bp) or to the tcpA of biotype classical (617 bp). All strains belonging to the novel epidemic serogroup O139 generated a 471-bp fragment identical to El Tor tcpA. The present study suggests that there may be an association between non-O1 serogroup and tcpA type.

Bacterial Outer Membrane Proteins↗
PubMed1995

Modulation of DNA adduct formation by successive exposures of DNA to small and bulky chemical carcinogens.

The effect of a carcinogen-DNA adduct on the formation of a second adduct upon subsequent exposure to a second carcinogen was studied using (i) a modified Maxam-Gilbert chemical sequencing reaction and (ii) a DNA synthesis termination analysis. A DNA fragment of known sequence was reacted with micromolar concentrations of N-methyl-N-nitrosourea (MNU), (+)-r-7,t-8-dihydroxy-t-9,10- epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE), N-acetoxy-2- acetylaminofluorene (N-acetoxy-AAF), or aflatoxin B1-8,9-epoxide (AFB1 epoxide) singly or in successive double reactions. N-Acetoxy-AAF adducts were sensitive to the Maxam-Gilbert sequencing reaction for guanine; these adducts significantly blocked the formation of BPDE-guanine adducts. Treatment of DNA with BPDE, however, did not inhibit subsequent formation of N-acetoxy-AAF adducts. DNA synthesis termination analysis suggested that methylation of guanine altered subsequent arylation of guanine by N-acetoxy-AAF and AFB1 epoxide, and that combined treatment inhibited replication, an effect not seen after MNU treatment alone. Possible mechanisms for the modulation of carcinogen binding are discussed. It is concluded that not only is DNA damage by genotoxic carcinogens dependent upon both the chemical nature of the carcinogens and the nearest neighbors to target guanine bases, but that the effect of subsequent exposures to carcinogens is not always additive.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1994

Ability of human sera to neutralise the activity of Vero cytotoxins VT1, VT2 and variant forms of VT2.

Sera, from 17 patients with diarrhoea or haemolytic uraemic syndrome, and six healthy adults, were tested for neutralisation of Vero cytotoxins (VT). For all 17 patients there was evidence of infection with Escherichia coli O157. Sera from two controls but from none of the patients neutralised VT1, although two patients were infected by strains producing VT1 and VT2. Sera from all six controls and 14 patients neutralised VT2 derived from strains 933 and E32511, but not variant forms of VT2 derived from strains E32511, E57, B2F1 and H.1.8. This neutralising activity warrants further investigation, especially as many O157 VTEC carry both VT2 and VT2 variant genes.

Adolescent↗
PubMed1994

The use of gene probes, immunoassays and tissue culture for the detection of toxin in Vibrio cholerae non-O1.

Vibrio cholerae non-O1 strains were screened for the presence of cholera enterotoxin (CT) genes by means of digoxigenin-labelled polynucleotide CTA and CTB probes. In-vitro production of CT was investigated by the Y1 mouse adrenal cell assay, enzyme-linked immunosorbent assay (ELISA) and a commercial, reversed passive latex agglutination (RPLA) kit. Only two (0.25%) of 790 strains tested gave positive results with the CTA and CTB probes. The production of other bacterial cytotoxin(s) made it impossible to use the characteristic cell-rounding effect on Y1 cells for the detection of CT. CT production by the probe-positive strains was confirmed by the immunoassays. Two hundred and fifty-two of the 788 probe-negative strains were tested by both cell assay and immunoassays. Of these, 90% produced cytotoxin(s) in the cell assay. In addition, 37% gave positive results in CT-ELISA, but negative results with LT-ELISA and VET-RPLA. These results indicate the presumed presence of a toxin in V. cholerae non-O1 that is able to bind GM1 and react with antisera to CT, but which is not identical to CT.

Cell Line↗