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D G Smith

Publications and source records attributed to D G Smith.

At least 37 records · Page 2Linked to original sources
PubMed2001

Ancient mitochondrial DNA evidence for prehistoric population movement: the Numic expansion.

The mitochondrial DNA of modern Native Americans has been shown to fall into one of at least five haplogroups (A, B, C, D, or X) whose frequencies differ among tribal groups. The frequencies of these five haplogroups in a collection of ancient individuals from Western Nevada dating to between approximately 350-9,200 years BP were determined. These data were used to test the hypothesis, supported by archaeological and linguistic data, that the current inhabitants of the Great Basin, the Numic speakers, are recent immigrants into the area who replaced the previous non-Numic inhabitants. The frequency distributions of haplogroups in the ancient and modern Native Americans differed significantly, suggesting that there is a genetic discontinuity between the ancient inhabitants and the modern Numic speakers, providing further support for the Recent Numic Expansion hypothesis. The distribution of mitochondrial haplogroups of the ancient inhabitants of the Great Basin is most similar to those of some of the modern Native American inhabitants of California.

Anthropology, Physical↗
PubMed2001

Major histocompatibility complex class II polymorphisms in Macaca mulatta: factors influencing comprehensive genotyping of Macaca mulatta (Mamu)-DQA1 alleles by PCR-RFLP in archival samples.

In the last 5 years, HLA class II genotyping methods have been adapted for genotyping of class II loci in rhesus macaques. Since previously published typing protocols were used on samples that were collected and stored under ideal conditions, it was of interest to determine if these methods were adequate for genotyping a large collection of archival samples from which DNA had been isolated and stored under various conditions. Established macaque DQA1 typing protocols were modified to optimize the typing procedure and enhance the ability to successfully genotype DNA from samples that were of poor quality and/or quantity. Long-term storage of whole-blood buffy coats or stored DNA extracted from whole-blood buffy coats did not affect typing success; however, amplification and typing of DNA extracted from archival samples of plasma were difficult and resulted in a low success rate. This suggests that amplification and DQA1-genotyping of archival samples is possible with a modified protocol, but is influenced by the age and source of the sample, and to a lesser extent, the method used to extract DNA from sample substrates.

Animals↗
PubMed2001

Phylogenetic relationships among the macaques: evidence from the nuclear locus NRAMP1.

The macaques, genus Macaca, represent one of the most successful radiations within the Order Primates, with a geographical distribution that ranks second in size only to that of humans among extant primates. Although the number of macaque species recognized depends on the classification scheme used, most authors currently follow the classifications of either Fooden or Delson, both of whom recognize 19 extant macaque species. These two classifications differ in their placement of macaque species into more inclusive taxa (i.e., species groups). While researchers have attempted to use mitochondrial DNA (mtDNA) to resolve these phylogenetic relationships, different studies have generated conflicting conclusions. Consequently, we screened nuclear DNA sequences of a large number of macaques to determine if such data provide greater insight into the phylogenetic relationships among macaques. The data generated from the comparison of two (noncoding) introns within the natural resistance-associated macrophage protein 1 (NRAMP1) gene generally agree with the classification scheme of Delson. However, the data also support several novel observations. Specifically, the NRAMP1 data demonstrate that M. silenus and M. nemestrina lack nuclear genetic variation, while M. assamensis and M. radiata exhibit the greatest amount of genetic variation. In addition, these data suggest that M. fascicularis may not be as "primitive" (with respect to other members of the fascicularis group) as the mtDNA based data suggest.

Animals↗
PubMed2001

Plains cottonwood's last stand: can it survive invasion of Russian olive onto the Milk River, Montana floodplain?

Russian olive (Elaeagnus angustifolia L.) was introduced in 1950 onto one site on the Milk River floodplain, northern Montana, 10 km downstream from the Canada/United States border. To analyze dispersal of Russian olive from the point source between 1950 and 1999, we compared distribution, numbers, size structure, and mortality of Russian olive and plains cottonwood (Populus deltoides Marsh:) on an unregulated reach of the Milk River floodplain in southeastern Alberta and north-central Montana. Within 50 years, Russian olive in this reach has moved upriver into Alberta and downriver to the Fresno Reservoir. It is now present on 69 of the 74 meander lobes sampled, comprising 34%, 62%, and 61% of all Russian olive and plains cottonwood seedlings, saplings, and trees, respectively. On some meander lobes, Russian olive has colonized similar elevations on the floodplain as plains cottonwood and is oriented in rows paralleling the river channel, suggesting that recruitment may be related to river processes. Breakup ice had killed 400 Russian olive saplings and trees and damaged >1000 others on 30 of the meander lobes in 1996. Nevertheless, Russian olive now outnumbers cottonwood on many sites on the Milk River floodplain because its seeds can be dispersed by wildlife (particularly birds) and probably by flood water and ice rafts; seeds are viable for up to 3 years and germination can take place on bare and well-vegetated soils; and saplings and trees are less palatable to livestock and beaver than plains cottonwood. Without control, Russian olive could be locally dominant on the Milk River floodplain in all age classes within 10 years and replace plains cottonwood within this century.

Animals↗
PubMed2001

Corneal bee sting with retained stinger.

Bee stings of the cornea are rarely reported, but have the potential for causing serious ophthalmologic injuries. We present a case of corneal bee sting with retained stinger apparatus and associated iritis and discuss the pathologic mechanisms of injury, evaluation, and treatment of these uncommon presentations.

Adult↗
PubMed2001

The structure of phosphorylated GSK-3beta complexed with a peptide, FRATtide, that inhibits beta-catenin phosphorylation.

BACKGROUND: Glycogen synthase kinase-3 (GSK-3) sequentially phosphorylates four serine residues on glycogen synthase (GS), in the sequence SxxxSxxxSxxx-SxxxS(p), by recognizing and phosphorylating the first serine in the sequence motif SxxxS(P) (where S(p) represents a phosphoserine). FRATtide (a peptide derived from a GSK-3 binding protein) binds to GSK-3 and blocks GSK-3 from interacting with Axin. This inhibits the Axin-dependent phosphorylation of beta-catenin by GSK-3. RESULTS: Structures of uncomplexed Tyr216 phosphorylated GSK-3beta and of its complex with a peptide and a sulfate ion both show the activation loop adopting a conformation similar to that in the phosphorylated and active forms of the related kinases CDK2 and ERK2. The sulfate ion, adjacent to Val214 on the activation loop, represents the binding site for the phosphoserine residue on 'primed' substrates. The peptide FRATtide forms a helix-turn-helix motif in binding to the C-terminal lobe of the kinase domain; the FRATtide binding site is close to, but does not obstruct, the substrate binding channel of GSK-3. FRATtide (and FRAT1) does not inhibit the activity of GSK-3 toward GS. CONCLUSIONS: The Axin binding site on GSK-3 presumably overlaps with that for FRATtide; its proximity to the active site explains how Axin may act as a scaffold protein promoting beta-catenin phosphorylation. Tyrosine 216 phosphorylation can induce an active conformation in the activation loop. Pre-phosphorylated substrate peptides can be modeled into the active site of the enzyme, with the P1 residue occupying a pocket partially formed by phosphotyrosine 216 and the P4 phosphoserine occupying the 'primed' binding site.

Amino Acid Motifs↗
PubMed2001

Amputation. Preoperative assessment and lower extremity surgical techniques.

Amputation surgery is an important part of the treatment for severe limb disorders. The decision-making process must be done thoughtfully, remembering that blood flow is not the only issue. Many factors enter into the decision to perform a partial foot amputation or to perform a more proximal level amputation. Adherence to good surgical principles, proven techniques, and gentle soft tissue handling can make the difference between a successful and durable amputation or continued complications and frustrations.

Amputation, Surgical↗
PubMed2001

Kynurenine pathway metabolism in human astrocytes: a paradox for neuronal protection.

There is good evidence that the kynurenine pathway (KP) and one of its products, quinolinic acid (QUIN), play a role in the pathogenesis of neurological diseases, in particular AIDS dementia complex. Although QUIN has been shown to be produced in neurotoxic concentrations by macrophages and microglia, the role of astrocytes in QUIN production is controversial. Using cytokine-stimulated cultures of human astrocytes, we assayed key enzymes and products of the KP. We found that human astrocytes lack kynurenine hydroxylase so that large amounts of kynurenine and the QUIN antagonist kynurenic acid were produced. However, the amounts of QUIN that were synthesized were subsequently completely degraded. We then showed that kynurenine in concentrations comparable with those produced by astrocytes led to significant production of QUIN by macrophages. These results suggest that astrocytes alone are neuroprotective by minimizing QUIN production and maximizing synthesis of kynurenic acid. However, it is likely that, in the presence of macrophages and/or microglia, astrocytes become indirectly neurotoxic by the production of large concentrations of kynurenine that can be secondarily metabolized by neighbouring or infiltrating monocytic cells to form the neurotoxin QUIN.

AIDS Dementia Complex↗
PubMed2001

Emergency physician practice and steroid use in the management of acute exacerbations of asthma.

This study seeks to determine patterns of emergency physician (EP) practice regarding steroid use in the management of acute asthma attacks in the emergency department (ED), and to compare practices of academic and private practice EPs. Two hundred eight questionnaires were mailed to academic and private practice EPs. The survey requested information regarding the preferred initial route (oral or intravenous) for steroid administration; the initial dose of steroid; the preferred steroid regimen for outpatient management; and whether or not inhaled steroids were routinely prescribed at the time of discharge. The overall response rate was 74%; 91% for the academic EPs and 56% for private practice EPs. Sixty-five percent (99/143) of all EPs used the intravenous route for their initial dose of steroids. A significantly greater percentage of private practice EPs (45/58 or 78%) used intravenous steroids compared with academic EPs (54/95 or 57%; P = .009). A total of 41% (63/153) of EPs used a tapering steroid regime for outpatient therapy; a significantly greater percentage (34/58 or 59%; P = .0006) of private practice EPs used a tapering regimen of steroids compared with academic EPs (29/95 or 31%). A total of 32%(31) academic and 34% (20) private practice EPs prescribed inhaled steroids as part of their routine discharge instructions. Emergency physician practice patterns regarding initial steroid route of administration and dose, and outpatient-dosing regimens are variable. Only a minority of EPs prescribe steroid metered dose inhalers as part of their outpatient management of asthma.

Acute Disease↗
PubMed2001

Back pain as a secondary disability in persons with lower limb amputations.

OBJECTIVE: To evaluate the frequency, duration, intensity, and interference of back pain in a sample of persons with lower limb amputations. DESIGN: Retrospective, cross-sectional survey. SETTING: Community-based survey from clinical databases. PARTICIPANTS: Participants who were 6 or more months post lower limb amputation (n = 255). INTERVENTION: An amputation pain survey that included several standardized pain measures. MAIN OUTCOME MEASURES: Frequency, duration, intensity, and interference of back pain. RESULTS: Of the participants who completed the survey (return rate, 56%), 52% reported experiencing persistent, bothersome back pain. Of these, 43% reported average back pain intensity in the mild range (1-4 on 0-10 rating scale) and 25% reported pain of moderate intensity (5-6 on 0-10 scale). Most respondents with back pain rated the interference of their pain on function as none to minimal. However, nearly 25% of those with back pain described it as frequent, of severe intensity (>or=7 on 0-10 scale), and as severely interfering with daily activities including social, recreational, family, and work activities. CONCLUSIONS: Back pain may be surprisingly common in persons with lower limb amputations, and, for some who experience it, may greatly interfere with function.

Activities of Daily Living↗
PubMed2001

Human immunodeficiency virus 1 expression in the female genital tract in association with cervical inflammation and ulceration.

OBJECTIVES: Determining the source of human immunodeficiency virus 1 in the female genital tract and identifying factors that influence the amount of virus shed are important in the understanding of heterosexual human immunodeficiency virus 1 transmission. STUDY DESIGN: Cervicovaginal human immunodeficiency virus 1 ribonucleic acid shedding was quantified before and after treatment of cervical squamous intraepithelial lesions in 14 women. Genotypic analysis was performed on peptide HIV-1 env gp120 of the major human immunodeficiency virus 1 species in plasma and cervicovaginal lavage of selected samples. RESULTS: At 2 to 4 weeks after treatment, when cervices were inflamed and ulcerated, human immunodeficiency virus 1 ribonucleic acid in lavage samples increased 1.0 to 4.4 log 10. Genotypic analysis showed significant differences between the predominant human immunodeficiency virus 1 species in paired plasma and lavage samples from 2 of 4 women, suggesting that the increase in human immunodeficiency virus 1 was the result of local viral replication. CONCLUSIONS: Cervical inflammation and ulceration are associated with local human immunodeficiency virus 1 expression, which increases as much as 10,000-fold the amount of human immunodeficiency virus 1 shed into genital secretions. This may explain why sexually transmitted diseases are important risk factors for human immunodeficiency virus transmission.

Adult↗
PubMed2001

Effect of trans-tibial prosthesis pylon flexibility on ground reaction forces during gait.

This study explored the effects of trans-tibial prosthesis pylon flexibility on ground reaction forces (GRFs) associated with walking and step-down. Four (4) active subjects with unilateral trans-tibial amputation and pylon lengths ranging from 4.9 cm to 25.9 cm were studied wearing an aluminium (rigid) pylon and a nylon (more flexible) pylon. Ground reaction forces were collected for the amputated limb during walking at pre-measured self-selected velocity and when stepping down from a 20 cm box. Pylon material significantly affected the magnitudes and patterns of GRFs in both tests. During walking, the most notable differences were seen in the anteroposterior (AP) direction. With the flexible pylon, the AP propulsive peak was greater (p=0.031), and the irregularities in the AP force curve were reduced. Additionally, when walking with the flexible pylon, the vertical peak associated with weight acceptance occurred earlier (p=0.010), the vertical terminal stance peak occurred later (p=0.012), and stance time was longer (p=0.010). During step-down, the vertical loading rate (p=0.010) and the peak vertical force (p=0.010) were greater with the more flexible pylon. Subjective feedback indicated that subjects could distinguish between the two pylons and felt that the nylon component was more comfortable, more flexible, and would enable them to walk more quickly. These results suggest that the pylon may be an influential component of the prosthesis with respect to gait and comfort, and that some degree of flexibility is desirable.

Adult↗
PubMed2001

Quinolinic acid is produced by macrophages stimulated by platelet activating factor, Nef and Tat.

Activated macrophages produce quinolinic acid (QUIN), a neurotoxin, in several inflammatory brain diseases including AIDS dementia complex. We hypothesized that IL1-beta, IL6, transforming growth factor (TGF-beta2 and platelet activating factor could increase macrophage QUIN production. And that the HIV-1 proteins Nef, Tat and gp41 may also increase synthesis of QUIN by macrophages. At 72 h there were significant increases in QUIN production in the cells stimulated with PAF (914 +/- 50 nM) and Nef (2781 +/- 162 nM), with somewhat less production by Tat stimulation (645 +/- 240 nM). The increases in QUIN production approximated in vitro concentrations of QUIN shown to be neurotoxic and correlated closely with indoleamine 2,3-dioxygenase induction. IL1-beta, IL6, TGF-beta2 and gp41 stimulation produced no significant increase in QUIN production. These results suggest that some of the neurotoxicity of PAF, nef and tat may be mediated by QUIN.

AIDS Dementia Complex↗
PubMed2001

IFN-beta1b induces kynurenine pathway metabolism in human macrophages: potential implications for multiple sclerosis treatment.

Interferon-beta(1b) (IFN-beta(1b)) has limited efficacy in the treatment of relapsing-remitting multiple sclerosis (RRMS). The kynurenine pathway (KP) is chiefly activated by IFN-gamma and IFN-alpha, leading to the production of a variety of neurotoxins. We sought to determine whether IFN-beta(1b) induces the KP in human monocyte-derived macrophages, as one explanation for its limited efficacy. Serial dilutions of IFN-beta(1b) (at concentrations comparable to those found in the sera of IFN-beta(1b)-treated patients) were added to human macrophage cultures. Supernatants were collected at various time points and assayed for the KP end product, quinolinic acid (QUIN). The effect of IFN-beta(1b) on the KP enzymes indoleamine 2,3-dioxygenase (IDO), 3-hydroxyanthranilate dioxygenase (3HAO), and quinolinate phosphoribosyltransferase (QPRTase) mRNA expression was assessed by semiquantitative RT-PCR. IFN-beta(1b) (> or =10 IU/ml) led to increased mRNA expression of both IDO and QUIN production (7901 +/- 715 nM) after 72 h at 50 IU/ml IFN-beta(1b) (p < 0.0001). This study demonstrates that IFN-beta(1b), in pharmacologically relevant concentrations, induces KP metabolism in human macrophages and may be a limiting factor in its efficacy in the treatment of MS. Inhibitors of the KP may be able to augment the efficacy of IFN-beta in MS.

Cells, Cultured↗
PubMed2001

Analysis of type 1 fimbriae expression in verotoxigenic Escherichia coli: a comparison between serotypes O157 and O26.

Previous research has shown that verotoxin-producing Escherichia coli (VTEC) O157 strains appear unable to express type 1 fimbriae although other serotypes such as O26 and O118 can. This study has investigated the molecular basis of this difference. The study confirmed the presence of a 16 bp deletion within the regulatory region of fimA (fim switch) in 63 VTEC O157 strains but not in other VTEC serotypes tested. The fim switch was shown to be detectable only in the phase off orientation in VTEC O157, but detection of the switch in the phase on orientation correlated with the degree of mannose-sensitive yeast agglutination in VTEC O26. Repair of the 16 bp deletion in the VTEC O157 fim switch region restored phase-variable expression of fimA in a permissive background. Non-O157 VTEC, especially O26 and O118, can be pathogenic in cattle; the role of type 1 fimbriae in this and colonization is discussed.

Animals↗
PubMed2001

Differences in levels of secreted locus of enterocyte effacement proteins between human disease-associated and bovine Escherichia coli O157.

Ongoing extensive epidemiological studies of verotoxin-carrying Escherichia coli O157 (stx(+) eae(+)) have shown this bacterial pathogen to be common in cattle herds in the United States and the United Kingdom. However, the incidence of disease in humans due to this pathogen is still very low. This study set out to investigate if there is a difference between strains isolated from human disease cases and those isolated from asymptomatic cattle which would account for the low disease incidence of such a ubiquitous organism. The work presented here has compared human disease strains from both sporadic and outbreak cases with a cross-section, as defined by pulsed-field gel electrophoresis, of E. coli O157 strains from cattle. Human (n = 22) and bovine (n = 31) strains were genotyped for carriage of the genes for Shiga-like toxin types 1, 2, and 2c; E. coli secreted protein genes espA, espB, and espP; the enterohemolysin gene; eae (intimin); ast (enteroaggregative E. coli stable toxin [EAST]); and genes for common E. coli adhesins. Strains were also phenotyped for hemolysin, EspP, Tir, and EspD expression as well as production of actin and cytoskeletal rearrangement associated with attaching and effacing (A/E) lesions on HeLa cells. The genotyping confirmed that there was little difference between the two groups, including carriage of stx(2) and stx(2c), which was similar in both sets. ast alleles were confirmed to all contain mutations that would prevent EAST expression. espP mutations were found only in cattle strains (5 of 30). Clear differences were observed in the expression of locus of enterocyte effacement (LEE)-encoded factors between strains and in different media. EspD, as an indicator of LEE4 (espA, -B, and -D) expression, and Tir levels in supernatants were measured. Virtually all strains from both sources could produce EspD in Luria-Bertani broth, although at very different levels. Standard trichloroacetic acid precipitation of secreted proteins from tissue culture medium produced detectable levels of EspD from the majority of strains of human origin (15 of 20) compared with only a few (4 of 20) bovine strains (P < 0.001), which is indicative of much higher levels of protein secretion from the human strains. Addition of bovine serum albumin carrier protein before precipitation and enhanced detection techniques confirmed that EspD could be detected after growth in tissue culture medium for all strains, but levels from strains of human origin were on average 90-fold higher than those from strains of bovine origin. In general, levels of secretion also correlated with ability to form A/E lesions on HeLa cells, with only the high-level protein secretors in tissue culture medium exhibiting a localized adherence phenotype. This research shows significant differences between human- and bovine-derived E. coli O157 (stx(+) eae(+)) strains and their production of certain LEE-encoded virulence factors. These data support the recent finding of Kim et al. (J. Kim, J. Nietfeldt, and A. K. Benson, Proc. Natl. Acad. Sci. USA 96:13288-13293, 1999) proposing different E. coli O157 lineages in cattle and humans and extend the differential to the regulation of virulence factors. Potentially only a subset of E. coli O157 isolates (stx(+) eae(+)) in cattle may be capable of causing severe disease in humans.

Adhesins, Bacterial↗
PubMed2001

Distribution of mitochondrial DNA lineages among Native American tribes of Northeastern North America.

The mtDNA haplogroups of 185 individuals from Native American tribes in Northeast North America were determined. A subset of these individuals was analyzed by sequencing hypervariable segments I and II of the control region. The haplogroup frequency distributions of populations in the Northeast exhibit regional continuity that predates European contact. A large amount of gene flow has occurred between Siouan-and Algonquian-speaking groups, probably due to an Algonquian intrusion into the Northeast. The data also support both the Macro-Siouan hypothesis and a relatively recent intrusion of Northern Iroquoians into the Northeast. These conclusions are consistent with archaeological and linguistic evidence.

Canada↗