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Biomedical subjects

T A Graham

Publications and source records attributed to T A Graham.

11 recordsLinked to original sources
PubMed2003

Prevalence of Escherichia coli O157:H7 and Salmonella spp. in surface waters of southern Alberta and its relation to manure sources.

The Oldman River watershed in southern Alberta, Canada, is an extensively irrigated region in which intensive agricultural practices have flourished. Concern over water quality in the basin has been expressed because of high levels of enteric disease indigenous to the region. To address these concerns, we conducted a 2-year study to estimate the prevalence of Escherichia coli O157:H7 and Salmonella spp. in surface water within the basin. This study is the first of its kind to identify E. coli O157:H7 repeatedly in surface water collected from a Canadian watershed. Prevalence of E. coli O157:H7 and Salmonella spp. in water samples was 0.9% (n = 1,483) and 6.2% (n = 1,429), respectively. While data examined at a regional level show a relationship between high livestock density and high pathogen levels in southern Alberta, statistical analysis of point source data indicates that predicted manure output from bovine, swine, and poultry feeding operations was not directly associated with either Salmonella spp. or E. coli O157:H7 prevalence. However, geography and weather variables, which are likely to influence bacterial runoff, were not considered in this model. We also postulate that variations in time, amount, and frequency of manure application onto agricultural lands may have influenced levels of surface-water contamination with these bacterial pathogens.

Alberta↗
PubMed2002

Escherichia coli O157:H7 infection in cows and calves in a beef cattle herd in Alberta, Canada.

Escherichia coli O157:H7 infection of cows and calves in a naturally-infected beef cattle herd in Alberta, Canada, was investigated over 2 years, encompassing two calf production cycles. In both years of the study, E. coli O157:H7 was isolated from the faeces of cows shortly after but not before parturition in late winter: 6/38 (16%) in 1996 and 13/50 (26%) in 1997. At < 1 week post-partum, 13/52 (25%) calves born in 1997 were shedding the organism. Faecal shedding of E. coli O157:H7 by cows and calves continued over the 7 weeks that they were in the calving pens, with the organism being isolated from the faeces of 2-18% of cows and 23-26% of calves during this period. Five weeks after they were moved onto a native grass pasture, all the calves and all but one cow in 1997 had ceased shedding the organism. When the calves were weaned in the fall, E. coli O157:H7 was isolated from the faeces of 0-1.5% of the calves 1 week prior to weaning and from 6-14% of the calves within 2 weeks after weaning. Parturition, calving pens and weaning appear to be important factors in maintaining E. coli O157:H7 infections in this beef cattle herd. Isolates from cows and calves during the immediate post-partum period were mostly of the same pulsed-field gel electrophoresis (PFGE) type of E. coli O157:H7. Similarly, at weaning a common PFGE type of E. coli O157:H7, which differed slightly from the post-partum PFGE type, was isolated from the calves. These typing data suggest a common source of infection for the animals as well as demonstrate clonal turnover of resident populations of this pathogen.

Animals↗
PubMed2002

Immunological characterization of Escherichia coli O157:H7 intimin gamma1.

Portions of the intimin genes of Escherichia coli O157:H7 strain E319 and of the enteropathogenic E. coli O127:H6 strain E2348/69 were amplified by PCR and cloned into pET-28a+ expression vectors. The entire 934 amino acids (aa) of E. coli O157:H7 intimin, the C-terminal 306 aa of E. coli O157:H7 intimin, and the C-terminal 311 aa of E. coli O127:H6 intimin were expressed as proteins fused with a six-histidine residue tag (six-His tag) in pET-28a+. Rabbit antisera raised against the six-His tag-full-length E. coli O157:H7 intimin protein fusion cross-reacted in slot and Western blots with outer membrane protein preparations from the majority of enterohemorrhagic and enteropathogenic E. coli serotypes which have the intimin gene. The E. coli strains tested included isolates from humans and animals which produce intimin types alpha (O serogroups 86, 127, and 142), beta1 (O serogroups 5, 26, 46, 69, 111, 126, and 128), gamma 1 (O serogroups 55, 145, and 157), gamma 2 (O serogroups 111 and 103), and epsilon (O serogroup 103) and a nontypeable intimin (O serogroup 80), results based on intimin type-specific PCR assays. Rabbit antisera raised against the E. coli O157:H7 C-terminal fusion protein were much more intimin type-specific than those raised against the full-length intimin fusion protein, but some cross-reaction with other intimin types was also observed for these antisera. In contrast, the monoclonal antibody Intgamma1.C11, raised against the C-terminal E. coli O157 intimin, reacted only with preparations from intimin gamma 1-producing E. coli strains such as E. coli O157:H7.

Adhesins, Bacterial↗
PubMed2001

Tcf4 can specifically recognize beta-catenin using alternative conformations.

Accumulation of the Wnt pathway effector beta-catenin is a hallmark of a number of cancers, including colon cancer. As beta-catenin accumulates in the cell, it forms a complex with Tcf family transcription factors and activates the transcription of several critical genes involved in cell proliferation. Because Tcf4 is the predominant Tcf factor present in colon cancer cells, drugs that specifically disrupt the beta-catenin-Tcf4 complex could be useful in treating colon cancers. Earlier structural and biochemical studies demonstrated that the central region of the beta-catenin binding domain of Tcf is essential for anchoring Tcf to beta-catenin via two conserved lysines in beta-catenin (called the charged 'buttons'). Here we report the crystal structure of a beta-catenin-Tcf4 complex at 2.0 A resolution. Our structural and mutagenesis studies show that Tcf4 docks specifically to beta-catenin using several distinct conformations in its essential central region. These conformations allow different glutamate residues in the central region of Tcf4 to form a salt bridge with the same critical charged button, Lys 312 of beta-catenin. We propose that this interaction may be the first event in beta-catenin-Tcf4 recognition.

Amino Acid Sequence↗
PubMed2000

Crystal structure of a beta-catenin/Tcf complex.

The Wnt signaling pathway plays critical roles in embryonic development and tumorigenesis. Stimulation of the Wnt pathway results in the accumulation of a nuclear beta-catenin/Tcf complex, activating Wnt target genes. A crystal structure of beta-catenin bound to the beta-catenin binding domain of Tcf3 (Tcf3-CBD) has been determined. The Tcf3-CBD forms an elongated structure with three binding modules that runs antiparallel to beta-catenin along the positively charged groove formed by the armadillo repeats. Structure-based mutagenesis defines three sites in beta-catenin that are critical for binding the Tcf3-CBD and are differentially involved in binding APC, cadherin, and Axin. The structural and mutagenesis data reveal a potential target for molecular drug design studies.

Amino Acid Motifs↗
PubMed1999

The role of gesture in children's learning to count.

The role of spontaneous gesture was examined in children's counting and in their assessment of counting accuracy. Eighty-five 2-, 3-, and 4-year-olds counted 6 sets of 2-, 4-, and 6-object arrays. In addition, children assessed the counting accuracy of a puppet whose gestures varied as he counted (i.e., gesture matched the number words, gesture mismatched the number words, no gesture at all). Results showed that the correspondence of children's speech and gesture varied systematically across the age groups and that children adhered to the one-to-one correspondence principle in gesture prior to speech. Moreover, children's correspondence of speech and gesture, adherence to the one-to-one principle in gesture, and assessment of the puppet's counting accuracy were related to children's counting accuracy. Findings are discussed in terms of the role that gesture may play in children's understanding of counting.

Attention↗
PubMed1997

Inter- and intraspecies comparison of the 16S-23S rRNA operon intergenic spacer regions of six Listeria spp.

The 16S-23S rRNA intergenic spacer (IGS) regions found in six Listeria species were characterized. PCR amplification of the 16S-23S IGS with a "generic primer" set generated products of about 340 bp (small) and 550 to 590 bp (large) with DNA from all Listeria strains tested. Seven Listeria monocytogenes serotype 4b strains and one L. monocytogenes serotype 4d strain also had an additional PCR product of ca. 360 bp. The 360-bp PCR product from one of these L. monocytogenes serotype 4b strains was identical in nucleotide sequence to the small 340-bp IGS, except that it contained an 18-bp tandem repeat. The small rRNA IGSs of L. innocua, L. ivanovii, L. seeligeri, L. welshimeri, and L. grayi were 83 to 99% homologous to that of L. monocytogenes. The large rRNA IGS of L. monocytogenes was 81 to 96% homologous to those of the other Listeria species and agreed with current taxonomic division among these species. The nucleotide sequences of the central 274 bp of the large rRNA IGS of strains from seven different L. monocytogenes serotypes were highly homologous; however, serotype-specific differences were noted, and four groups were identified within L. monocytogenes based on this analysis.

Animals↗
PubMed1997

Preclinical and clinical evaluation of broccoli supplements as inducers of glutathione S-transferase activity.

Previous studies suggest that cruciferous vegetables may provide protection against carcinogen exposure by inducing detoxification enzymes. ICR(Ha) mice were gavaged with broccoli tablets (1 g/kg), and colon tissues were collected after treatment. Glutathione S-transferase (GST) activity was assayed and peaked on days 1 and 2 after treatment, respectively (P = 0.03). Elevations in GST activity were attributed to the increased expression of mu and pi. These data supported a clinical assessment of broccoli supplements. Twenty-nine subjects at increased risk for colorectal cancer were randomized to group 1 (no cruciferous vegetables) or group 2 (broccoli supplements, 3 g/day) for 14 days. Blood samples and colon biopsies were obtained pre- and postintervention. No significant difference was observed between the GST activities of the control and broccoli supplementation groups posttreatment. Mean lymphocyte GST activity was 107% of baseline in the broccoli supplementation group (range, 79-158%) and 102% of baseline in the control group (range, 75-158 percent;). Correlation of the GST activities of blood lymphocytes and colon mucosa taken simultaneously suggested that the GST activity of blood lymphocytes may be used as a biomarker of the responsiveness of colon tissue to chemopreventive regimens. Future clinical studies evaluating cruciferous vegetables should consider using concentrated dietary supplements in subjects with a previous history of colorectal cancer.

Adult↗
PubMed1993

Conserved sequence and functional domains in satellite 2 from three families of salamanders.

Thirteen satellite 2 elements from Ambystoma talpoideum and 16 from Amphiuma tridactylum were cloned, sequenced, and compared with the satellite 2 consensus from Notophthalmus viridescens. These elements have maintained a high degree of similarity during the 65-200 Myr that the salamander families, represented by the three species, have been separated. The DNA sequences of the consensus elements from A. talpoideum and A. tridactylum are 81% similar, and both are approximately 65% similar to the N. viridescens consensus. In addition to its DNA sequence, the functional properties of satellite 2 have also been conserved. By selecting and analyzing clones that closely mimicked the consensus of each species, we were able to demonstrate that satellite 2 from each species was capable of promoting transcription after injection into Xenopus laevis oocytes and that synthetic transcripts of satellite 2 from each species were capable of catalyzing their own site-specific cleavage. These properties may be related to the process of retroposition, which was previously proposed to be responsible for the genomic proliferation of satellite 2. Each of these functional properties also has general biological interest.

Ambystoma↗
PubMedDate not supplied

Bacterial pathogens in rural water supplies in Southern Alberta, Canada.

Raw river and irrigation water in the Oldman River Basin in southern Alberta was tested for the presence of two bacterial pathogens, Escherichia coli O157:H7 and Salmonella spp., over the last 2 yr (2000-2001). The number of E. coli O157:H7 and Salmonella spp. isolated from raw water peaked during the summer months. While E. coli O157:H7 was only isolated from 11/802 (1.35%) of raw water samples over the entire sampling season in 2000 and from 16/806 (2.05%) of the samples in 2001, the pathogen was isolated one or more times from 10/35 (28.55%) sampling sites in 2000 and from 13/40 (32.55%) sampling sites in 2001. Salmonella was isolated from 44/802 (5.55%) of raw water samples in 2000 and from 122/822 (14.95%) of the samples in 2001; the pathogen was isolated one or more times from 25/35 (71.45%) sampling sites in 2000 and from 29/40 (72.55%) sampling sites in 2001. Certain sites had multiple pathogen isolations in the same year and from year to year. Salmonella Rublislaw was the most common Salmonella serovar isolated in both years, accounting for 52.45% of isolates.

Alberta↗