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Biomedical subjects

A E Stapleton

Publications and source records attributed to A E Stapleton.

At least 19 recordsLinked to original sources
PubMed2003

Ultraviolet radiation alters maize phyllosphere bacterial diversity.

Epiphytic bacteria are subjected to very stressful environments, including UV radiation. Bacterial assemblages on Zea mays (maize) leaves exposure were examined with and without UV-B radiation. Culture-independent molecular techniques were utilized for bacterial identification, diversity analysis and selection of putative UV exposure marker sequences. Few sequences corresponded to previously characterized phyllosphere bacteria. There was a strong tendency toward increased 16S rDNA sequence diversity in UV samples. Overall community structure was assessed using denaturing gel gradient electrophoresis; significant alterations in community structure were found in comparisons of phyllosphere bacterial samples from control and solar UV-B exposed plants.

Bacteria↗
PubMed2001

Intraspecific comparisons reveal differences in the pattern of ultraviolet radiation responses in four maize (Zea mays L.) varieties.

Four maize (Zea mays L.) varieties were examined for ultraviolet radiation-induced changes in leaf rolling, biomass, fluctuating leaf asymmetry and DNA damage. Short-term dose-response curves for each response were constructed and responses in each line compared. The four varieties each exhibited a different pattern of tolerance and reactivity, ranging from B73, which was tolerant in all four measures, to TS1, which was affected in DNA damage levels and leaf rolling but unaffected in biomass accumulation and fluctuating leaf asymmetry. The pattern of ultraviolet radiation responses allows us to narrow the possibilities for the source of the defect in reactive varieties. The four varieties tested include inbred parents that have been used to construct recombinant inbred lines and a variety that is found in the background of the engineered RescueMu transposon mutagenesis lines. These dose-response curves and variety comparisons provide the foundation for genetic dissection of the mechanisms of ultraviolet radiation responses in maize.

Biomass↗
PubMed2000

A prospective study of asymptomatic bacteriuria in sexually active young women.

BACKGROUND: Asymptomatic bacteriuria is common in young women, but little is known about its pathogenesis, natural history, risk factors, and temporal association with symptomatic urinary tract infection. METHODS: We prospectively evaluated 796 sexually active, nonpregnant women from 18 through 40 years of age over a period of six months for the occurrence of asymptomatic bacteriuria (defined as at least 10(5) colony-forming units of urinary tract pathogens per milliliter). The women were patients at either a university student health center or a health maintenance organization. Periodic urine cultures were taken, daily diaries were kept, and regularly scheduled interviews were performed. Escherichia coli strains were tested for hemolysin, the papG genotype, and the ribosomal RNA type. RESULTS: The prevalence of asymptomatic bacteriuria (the proportion of urine cultures with bacteriuria in asymptomatic women) was 5 percent (95 percent confidence interval, 4 percent to 6 percent) among women in the university group and 6 percent (95 percent confidence interval, 5 percent to 8 percent) among women in the health-maintenance-organization group. Persistent asymptomatic bacteriuria with the same E. coli strain was rare. Symptomatic urinary tract infection developed within one week after 8 percent of occasions on which a culture showed asymptomatic bacteriuria, as compared with 1 percent of occasions when asymptomatic bacteriuria was not found (P<0.001). Asymptomatic bacteriuria was associated with the same risk factors as for symptomatic urinary tract infection, particularly the use of a diaphragm plus spermicide and sexual intercourse. CONCLUSIONS: Asymptomatic bacteriuria in young women is common but rarely persists. It is a strong predictor of subsequent symptomatic urinary tract infection.

Adolescent↗
PubMed2000

Risk factors for recurrent urinary tract infection in young women.

To define host factors associated with an increased risk of recurrent urinary tract infection (RUTI), a case-control study was conducted in 2 populations: university women and health maintenance organization enrollees. Case patients were 229 women 18-30 years old with RUTIs; control subjects were 253 randomly selected women with no RUTI history. In a multivariate model, independent risk factors for RUTI included recent 1-month intercourse frequency (odds ratio [OR], 5.8; 95% confidence interval [CI], 3.1-10.6 for 4-8 episodes), 12-month spermicide use (OR, 1.8; 95% CI, 1.1-2.9), and new sex partner during the past year (OR, 1.9; 95% CI, 1.2-3.2). Two newly identified risk factors were age at first urinary tract infection (UTI) </=15 years (OR, 3.9; 95% CI, 1.9-8.0) and UTI history in the mother (OR, 2.3; 95% CI, 1.5-3.7). Blood group and secretor phenotype were not associated with RUTI. In young women, risk factors for sporadic UTI are also risk factors for recurrence. Two predictors suggest that genetic/long-term environmental exposures also predispose to RUTI.

Adolescent↗
PubMed2000

Influence of the normal menstrual cycle on vaginal tissue, discharge, and microflora.

The objective of this study was to examine genital tissue, vaginal fluid, and vaginal microbial flora at 3 phases of the menstrual cycle in asymptomatic women. Vaginal examinations were performed 3 times in 74 women: at the menstrual phase (days 1-5), the preovulatory phase (days 7-12), and the postovulatory phase (days 19-24). Flora of 50 women without bacterial vaginosis (BV) was analyzed separately from flora of 24 women with BV. The volume of vaginal discharge increased and the amount of cervical mucus decreased over the menstrual cycle. Among subjects without BV, the rate of recovery of any Lactobacillus changed little (range, 82% to 98%; P = .2); however, a small increase occurred in the rate of recovery of heavy (3+ to 4+ semiquantitative) growth of Lactobacillus over the menstrual cycle (P = .04). A linear decrease occurred in the rate of recovery of heavy growth of any non-Lactobacillus species, from 72% at days 1-5 to 40% at days 19-24 (P = .002). A linear decrease also occurred in the rate of recovery of Prevotella species, from 56% on days 1-5 to 28% on days 19-24 (P =. 007), while a small linear increase occurred in the rate of recovery of Bacteroides fragilis (P=.05). Among subjects with BV, the only significant change was an increase in the rate of recovery of Lactobacillus, from 33% at days 1-5 to 54% at days 19-24 (P = .008). Among all subjects, the rate of recovery of heavy growth of Lactobacillus increased over the menstrual cycle and, in contrast, the concentration of non-Lactobacillus species tended to be higher at menses, which is evidence that the vaginal flora becomes less stable at this time.

Adult↗
PubMed2000

Epithelial cell layer thickness and immune cell populations in the normal human vagina at different stages of the menstrual cycle.

OBJECTIVE: The aim of our study was to examine vaginal tissue during 3 phases of the menstrual cycle for the number of cell layers and epithelial immune cells. STUDY DESIGN: Vaginal biopsies were performed during 3 phases of the normal menstrual cycle (menstrual, days 1-5; preovulatory, days 7-12; and postovulatory, days 19-24) in 74 subjects. A subset of women had vaginal tissues stained with specific monoclonal antibody markers for Langerhans cells (CD1a), macrophages (KP1), T and B lymphocytes (CD4, CD8, CD21) and neutrophils (CD15). The number of cell layers and the number of immune cells in the vaginal tissue biopsy specimen were determined by a single observer who was blinded to clinical data. RESULTS: At 3 phases of the normal menstrual cycle, the mean number of epithelial cell layers underwent a small but statistically significant decrease from 27.8 +/- 0.7 on days 1-5 and 28.1 +/- 0.6 on days 7-12 to 26.0 +/- 0.7 on days 19-24 of the cycle (P =.01). Nonovulating women had a reduced mean epithelial cell layer count on days 7-12 (23.7 +/- 1. 4) compared with the epithelial cell layer count in ovulating women (28.8 +/- 0.7; P =.005). No significant changes were observed in the mean number per high-power field of Langerhans cells, macrophages, CD4 or CD8 lymphocytes, and neutrophil cell populations during the 3 phases of the cycle. B lymphocytes were not observed in the vaginal tissues. CONCLUSION: A small but statistically significant reduction in the number of vaginal epithelial cells was observed over the menstrual cycle. This reduction is not likely to be clinically significant. Immune cell populations in the vaginal tissues appeared stable throughout the menstrual cycle.

Adult↗
PubMed1998

The P histo-blood group-related glycosphingolipid sialosyl galactosyl globoside as a preferred binding receptor for uropathogenic Escherichia coli: isolation and structural characterization from human kidney.

The P histo-blood group-related glycosphingolipid, sialosyl galactosyl globoside (SGG), has recently been implicated as a preferred binding receptor for uropathogenic Escherichia coli [Stapleton, A. E., Stroud, M. R., Hakomori, S., and Stamm, W. E. (1998) Infect. Immun. 66, 3856-3861]. We report here the purification and complete structural characterization of SGG from normal human kidney. Using metabolically [35S]-labeled E. coli as a probe, a monosialylated glycosphingolipid was isolated to homogeneity. The glycosphingolipid was purified by a combination of high-performance liquid chromatography and preparative high-performance thin-layer chromatography and its structure unambiguously elucidated by 1H NMR, electrospray ionization mass spectrometry, and methylation analysis. Its primary structure was shown to be identical to a previously characterized, developmentally regulated, globo-series glycolipid thought to be unique to human teratocarcinoma. The significance of this structure as a unique receptor in human kidney for uropathogenic E. coli and its role in the pathogenesis of urinary tract infections are discussed.

Carbohydrate Conformation↗
PubMed1998

Inverse association of H2O2-producing lactobacilli and vaginal Escherichia coli colonization in women with recurrent urinary tract infections.

Women with recurrent urinary tract infection (UTI) often demonstrate persistent vaginal colonization with Escherichia coli. Since strains of lactobacilli that produce hydrogen peroxide inhibit the growth of E. coli, the absence of these strains may predispose to E. coli colonization and to UTI. To test this hypothesis, vaginal introital cultures were obtained from 140 women, 65 with recurrent UTI (case-patients) and 75 without (controls). Vaginal E. coli colonization was significantly more frequent in case-patients than controls (35% vs. 11%; P < .001) and in women without H2O2-positive lactobacilli than in women with (odds ratio [OR], 4.0; P = .01). Spermicide use was associated with greater risk of vaginal E. coli colonization (OR, 12.5; P < .001) and with absence of H2O2-positive lactobacilli (OR, 2.9; P = .04). The inverse association between H2O2-positive lactobacilli and vaginal E. coli colonization remained in case-patients after controlling for spermicide use (OR, 6.5; P = .02). Thus, absence of H2O2-positive lactobacilli may be important in the pathogenesis of recurrent UTI by facilitating E. coli introital colonization.

Adult↗
PubMed1998

Cytotoxicity of hemolytic, cytotoxic necrotizing factor 1-positive and -negative Escherichia coli to human T24 bladder cells.

Approximately one-half of Escherichia coli isolates from patients with cystitis or pyelonephritis produce the pore-forming cytotoxin hemolysin, a molecule with the capacity to lyse erythrocytes and a range of nucleated cell types. A second toxin, cytotoxic necrotizing factor 1 (CNF1), is found in approximately 70% of hemolytic, but rarely in nonhemolytic, isolates. To evaluate the potential interplay of these two toxins, we used epidemiological and molecular biologic techniques to compare the cytotoxicity of hemolytic, CNF1(+), and CNF1(-) cystitis strains toward human T24 bladder epithelial cells in vitro. A total of 29 isolates from two collections of cystitis-associated E. coli were evaluated by using methylene blue staining of bladder monolayers at 1-h intervals after inoculation with each strain. Most (20 of 29) isolates damaged or destroyed the T24 monolayer (less than 50% remaining) within 4 h after inoculation. As a group, CNF1(+) isolates from one collection (11 strains) were less cytotoxic at 4 h than the CNF1(-) strains in that collection (P = 0.009), but this pattern was not observed among isolates from the second collection (18 strains). To directly evaluate the role of CNF1 in cytotoxicity of hemolytic E. coli without the variables present in multiple clinical isolates, we constructed mutants defective in production of CNF1. Compared to the CNF1(+) parental isolates, no change in cytotoxicity was detected in these cnf1 mutants. Our results indicate that CNF1 does not have a detectable effect on the ability of hemolytic E. coli to damage human bladder cell monolayers in vitro.

Bacterial Toxins↗
PubMed1998

The globoseries glycosphingolipid sialosyl galactosyl globoside is found in urinary tract tissues and is a preferred binding receptor In vitro for uropathogenic Escherichia coli expressing pap-encoded adhesins.

Women with a history of recurrent Escherichia coli urinary tract infections (UTIs) are significantly more likely to be nonsecretors of blood group antigens than are women without such a history, and vaginal epithelial cells (VEC) from women who are nonsecretors show enhanced adherence of uropathogenic E. coli isolates compared with cells from secretors. We previously extracted glycosphingolipids (GSLs) from native VEC and determined that nonsecretors (but not secretors) selectively express two extended globoseries GSLs, sialosyl galactosyl globoside (SGG) and disialosyl galactosyl globoside (DSGG), which specifically bound uropathogenic E. coli R45 expressing a P adhesin. In this study, we demonstrated, by purifying the compounds from this source, that SGG and DSGG are expressed in human kidney tissue. We also demonstrated that SGG and DSGG isolated from human kidneys bind uropathogenic E. coli isolates expressing each of the three classes of pap-encoded adhesins, including cloned isolates expressing PapG from J96, PrsG from J96, and PapG from IA2, and the wild-type isolates IA2 and R45. We metabolically 35S labeled these five E. coli isolates and measured their relative binding affinities to serial dilutions of SGG and DSGG as well as to globotriaosylceramide (Gb3) and globotetraosylceramide (Gb4), two other globoseries GSLs present in urogenital tissues. Each of the five E. coli isolates bound to SGG with the highest apparent avidity compared with their binding to DSGG, Gb3, and Gb4, and each isolate had a unique pattern of GSL binding affinity. These studies further suggest that SGG likely plays an important role in the pathogenesis of UTI and that its presence may account for the increased binding of E. coli to uroepithelial cells from nonsecretors and for the increased susceptibility of nonsecretors to recurrent UTI.

Adhesins, Escherichia coli↗
PubMed1997

An Arabidopsis photolyase mutant is hypersensitive to ultraviolet-B radiation.

Photolyases are DNA repair enzymes that use energy from blue light to repair pyrimidine dimers. We report the isolation of an Arabidopsis thaliana mutant (uvr2-1) that is defective in photorepair of cyclobutylpyrimidine dimers (CPDs). Whereas uvr2-1 is indistinguishable from wild type in the absence of UV light, low UV-B levels inhibit growth and cause leaf necrosis. uvr2-1 is more sensitive to UV-B than wild type when placed under white light after UV-B treatment. In contrast, recovery in darkness or in light lacking photoreactivating blue light results in equal injury in uvr2-1 and wild type. The uvr2-1 mutant is unable to remove CPDs in vivo, and plant extracts lack detectable photolyase activity. This recessive mutation segregates as a single gene located near the top of chromosome 1, and is a structural gene mutation in the type II CPD photolyase PHR1. This mutant provides evidence that CPD photolyase is required for plant survival in the presence of UV-B light.

Apoenzymes↗
PubMed1997

Urovirulence determinants in Escherichia coli strains causing prostatitis.

To define the urovirulence properties of Escherichia coli strains producing prostatitis, E. coli strains isolated from men with acute (7 strains) or chronic (23) prostatitis were compared with E. coli isolates from women with pyelonephritis (30), acute cystitis (60), or complicated urinary tract infection (UTI; 30). Strains from prostatitis patients were significantly more likely to express hemolysin than were strains causing complicated UTI (73% vs. 43%; P = .02) and more often demonstrated hybridization with the cytotoxic necrotizing factor-1 (CNF-1) probe (63%) than did strains from women (44%-48%). P fimbrial expression was highest among pyelonephritis (73%) and prostatitis strains (53%) and lowest among E. coli from women with complicated UTI (23%) and cystitis (30%; P < .05, prostatitis strains vs. either of the latter 2 groups). Results suggest that E. coli strains producing prostatitis generally possess urovirulence profiles similar to those of strains from women with acute uncomplicated pyelonephritis and that hemolysin and CNF-1 are especially prevalent in prostatitis strains.

Acute Disease↗
PubMed1997

Characteristics and prevalence within serogroup O4 of a J96-like clonal group of uropathogenic Escherichia coli O4:H5 containing the class I and class III alleles of papG.

The recent discovery of a geographically dispersed clonal group of Escherichia coli O4:H5 that includes prototypic uropathogenic strain J96 prompted us to determine the prevalence of J96-like strains within serogroup O4 and to further assess the characteristics of such strains. We used O:K:H;F serotyping, PCR-based genomic fingerprinting, pulsed-field gel electrophoresis (PFGE), multilocus enzyme electrophoresis (MLEE), and PCR detection of the three papG alleles and of the cytotoxic necrotizing factor 1 (cnf1) and aerobactin (aer) gene sequences to characterize the 15 O4 strains among 336 E. coli isolates from three clinical collections (187 from mixed-source bacteremia, 75 from urosepsis, and 74 from acute cystitis). J96-like strains constituted approximately half of the O4 strains, or 2% of the total population. In contrast to other O4 strains, the J96-like strains characteristically exhibited specific group III capsular antigens, the H5 flagellar and F13 fimbrial antigens, a distinctive PCR genomic fingerprint, the class III papG allele (plus, in 50% of strains, the enigmatic class I papG allele), and cnf1 but lacked aer. A subset of these strains was remarkably homogeneous with respect to all these characteristics and exhibited a distinctive PFGE fingerprint and MLEE pattern. These findings clarify the epidemiological relevance of J96 as a model extraintestinal pathogen, provide further evidence of the class I papG allele outside of strain J96, and offer insights into the evolution of E. coli serogroup O4.

Adhesins, Escherichia coli↗
PubMed1996

A prospective study of risk factors for symptomatic urinary tract infection in young women.

BACKGROUND: Although acute urinary tract infections are common in young women, the associated risk factors have not been defined prospectively. METHODS: We recruited sexually active young women who were starting a new method of contraception at a university health center or a health maintenance organization (HMO) and monitored them for six months for symptomatic urinary tract infections. Daily diaries and serial interviews were used to collect data on potential risk factors. RESULTS: Among 796 women, the incidence of urinary tract infections per person-year was 0.7 in the university cohort (mean age, 23 years; n = 348) and 0.5 in the HMO cohort (mean age, 29; n = 448). In both cohorts, there were strong dose-response relations between the risk of infection and both recent use of a diaphragm with spermicide (respective relative risks for one, three, and five days of use in the past week, 1.42, 2.83, and 5.68 in the university cohort, P<0.001; and 1.29, 2.14, and 3.54 in the HMO cohort, P=0.04) and recent sexual intercourse (respective relative risks for one, three, and five days with intercourse in the past week, 1.37, 2.56, and 4.81 in the university cohort, P<0.001; and 1.24, 1.91, and 2.96 in the HMO cohort, P=0.002). The risk of acute infection was also associated with a history of recurrent infection (relative risk, 5.58 in the university group and 2.10 in the HMO group) but not with cervical-cap use, ABO-blood-group nonsecretor phenotype, or delayed postcoital voiding. CONCLUSIONS: Among sexually active young women the incidence of symptomatic urinary tract infection is high, and the risk is strongly and independently associated with recent sexual intercourse, recent use of a diaphragm with spermicide, and a history of recurrent urinary tract infections.

Acute Disease↗
PubMed1995

Hemagglutination, adherence, and surface properties of vaginal Lactobacillus species.

To address the poorly understood mechanisms through which lactobacilli adhere to vaginal epithelial cells (VECs), 65 wild type lactobacilli isolated from the vaginal flora of young women and 3 American Type Culture Collection Lactobacillus strains were studied. Group I isolates (n = 56) hemagglutinated sheep, rabbit, and human red blood cells (RBCs) and adhered poorly to VECs. In contrast, all 4 group II strains hemagglutinated sheep and human but not rabbit RBCs, adhered in large numbers to VECs, and were identical in five phenotypic tests and DNA-DNA hybridization. Eight other strains (group III) hemagglutinated all RBC types studied, adhered avidly to VECs, and had identical protein and hybridization patterns but showed heterogeneous enzyme activities. Although most wild type lactobacilli from the vaginal flora of young women adhered poorly to VECs, selected isolates (groups II and III) adhered in large numbers, demonstrated specific and reproducible hemagglutination patterns, and may have specific mechanisms of attachment to VECs.

Animals↗