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Biomedical subjects

P M Webb

Publications and source records attributed to P M Webb.

At least 37 records · Page 2Linked to original sources
PubMed1999

HIV immunization: acceptability and anticipated effects on sexual behavior among adolescents.

Adolescents rated hypothetical human immunodeficiency virus vaccines described as 90% and 50% efficacious and discussed how immunization might influence behavior of their peers. The low-efficacy vaccine was largely unacceptable and most believed immunization with the high-efficacy vaccine would cause increased risk behaviors. Immunization programs will need to address vaccine acceptability issues and behavioral responses to immunization.

AIDS Vaccines↗
PubMed1999

Stress-buffering factors related to adolescent coping: a path analysis.

To uncover those factors that buffer the impact of stressful negative experiences on adolescent adjustment, a theoretical model of adolescent stress and coping, with social support and social problem solving proposed as moderators, was investigated using path analysis. The study was conducted with 122 ninth-and tenth-grade nonreferred high school students. Using the LISREL statistical package (Jöreskog & Sörbom, 1986), it was found that a recursive loop leading from stress outcomes back to negative stressors did not allow for a successful solution to the model. However, the effects of stressful events on adjustment were mediated by coping resources, which included a combination of problem-solving abilities and social support. Overall, the findings replicated previous investigations that have demonstrated direct relationships among stressful life events, social support, problem solving, and adolescent adjustment. While a successful fit to the theoretical model was not attained, it was concluded that a refined model may provide a more acceptable solution.

Adaptation, Psychological↗
PubMed1998

Relationship between number of ovulatory cycles and accumulation of mutant p53 in epithelial ovarian cancer.

BACKGROUND: It has been suggested that increased numbers of ovulations might increase the risk of p53 gene (also known as TP53) mutation in the ovarian epithelium, thereby leading to the development of cancer. The data supporting this hypothesis have come from an observation that accumulation of p53 protein in epithelial ovarian cancer was strongly associated with increasing numbers of ovulatory cycles. We have further investigated the association between ovulatory history and p53 gene mutation by use of data from a large case-control study of ovarian cancer in Australia. METHODS: Tissue blocks were available for immunohistochemical analysis of p53 protein from 234 case subjects, aged 18-79 years, who had invasive epithelial ovarian cancer. Epidemiologic data were also available for these women and for 855 control subjects. Case-case comparisons were made by use of prevalence ratios and 95% confidence intervals (CIs), and case-control comparisons were made by use of odds ratios (ORs) and 95% CIs. All statistical tests were two-sided. RESULTS: There was no association between p53 accumulation and years of ovulation. Women with p53-positive cancers had undergone an average of 29.3 years of ovulation compared with 29.0 years of ovulation for women with p53-negative cancers (P=.8). Although the overall risk of ovarian cancer development was significantly increased in women who had undergone more years of ovulation (OR=2.17; 95% CI =1.54-3.05-for > or =35 years versus <23 years of ovulation), there was no difference in the risk associated with p53-positive and p53-negative cancers. CONCLUSIONS: These results confirm the association between increased ovulation and ovarian cancer risk but do not support the hypothesis that this association is due to an increased risk of p53 mutation with a greater number of ovulatory cycles.

Adult↗
PubMed1998

Milk consumption, galactose metabolism and ovarian cancer (Australia).

OBJECTIVES: It has been suggested that increased exposure to galactose, due to high consumption of dairy foods or reduced galactose metabolism, is associated with the development of ovarian cancer. We have investigated this in a large case-control study conducted in three Australian states between 1990 and 1993. METHODS: Approximately 800 histologically-confirmed cases, 800 community controls and 300 controls recruited through breast-screening clinics completed dietary questionnaires. Approximately 100 cases and all breast-screening controls also provided a blood sample for analysis of galactose-1-phosphate-uridyltransferase (GALT). RESULTS: Ovarian cancer risk was positively associated with increasing consumption of whole milk and other full-fat dairy foods, but was not associated with consumption of low-fat dairy foods and was inversely related to consumption of skimmed milk. There was no association between ovarian cancer and GALT except among women with abnormally low GALT who had a non-significant 2.5-fold increased risk of ovarian cancer. CONCLUSIONS: These data do not support the hypothesis that galactose plays a major role in the development of ovarian cancer and suggest that reported associations between milk consumption and ovarian cancer are due to the fat content of milk and not to lactose or galactose. An increased risk of ovarian cancer in women with abnormally low levels of GALT cannot, however, be ruled out.

Adolescent↗
PubMed1998

Effects of buoyancy on the diving behavior of northern elephant seals.

Marine mammals experience radical seasonal changes in body composition, which would be expected to affect their buoyancy in the water. The aim of this study was to examine the relationship between such changes in buoyancy and diving behavior in northern elephant seals Mirounga angustirostris. This was achieved by modifying the buoyancy of 13 juvenile elephant seals translocated from Año Nuevo State Reserve, CA, USA, and released at various sites in Monterey Bay, CA, USA. The buoyancy of each seal was calculated and was increased or decreased using syntactic foam or lead weights, and their diving behavior was recorded as they returned to Año Nuevo. The seals were divided into three groups: increased buoyancy (B+), reduced buoyancy (B-) and control seals (Bc). Mean descent rates were 0.77+/-0.3 ms-1 for the B+ seals, 0.82+/-0.2 ms-1 for the control seals and 0.87+/-0.3 ms-1 for the B- seals, and were significantly different. Mean ascent rates for the three treatments were 0.82+/-0.3 ms-1 for the B+ seals, 0.86+/-0.3 ms-1 for the control seals and 0.82+/-0.3 ms-1 for the B- seals. All the B+ seals ascended faster than they descended, while four of the five B- seals descended faster than they ascended. There was a significant negative correlation between buoyancy and descent rate, with less buoyant seals descending faster than more buoyant seals. There was, however, no correlation between ascent rate and buoyancy. This suggests that seals may use negative buoyancy to drift passively during descent, but that all seals may swim continuously during ascent. There was a significant correlation between buoyancy and the drift descent rate of C-type drift dives, including upwards drift in the most buoyant seal. Buoyancy was not correlated with diving depth, trip duration, dive duration or surface-interval duration. This study demonstrates that buoyancy plays a significant role in shaping diving behavior in northern elephant seals and that elephant seals may adjust their behavior to suit their buoyancy, rather than adjusting their buoyancy to suit a dive. This study also validated the truncated cones method of calculating body composition in this species by comparing it with body composition determined using tritium dilution.

Adipose Tissue↗
PubMed1997

Gastric cancer, gastritis and plasma vitamin C: results from an international correlation and cross-sectional study. The Eurogast Study Group.

Low intake of foods rich in vitamin C is associated with an increased risk of gastric cancer, and geographic variation in average vitamin C intake, therefore, could explain some of the wide international variation in gastric cancer rates. This multicentre study investigated the relationships between plasma levels of vitamin C, as an indicator of vitamin C intake, and gastric cancer rates, markers of gastritis and other socio-demographic variables. Fasting plasma samples from about 1,400 individuals from 9 centres in 7 countries worldwide were assayed for total vitamin C using a fluorometric assay. There was no association between average plasma vitamin C levels and either gastric cancer mortality or incidence rates in the populations studied. Therefore, variation in fasting plasma vitamin C levels, as an indicator of consumption of vitamin C, does not appear to explain any of the wide geographic variation in gastric cancer rates. Furthermore, there was no association between plasma vitamin C levels and Helicobacter pylori infection, low serum levels of pepsinogen A (as a marker of severe chronic atrophic gastritis) or the presence of DNA adducts in blood leukocyte DNA. Multivariate models showed that fasting plasma vitamin C levels were associated positively with female sex, higher levels of education, never having smoked and increasing height and negatively with number of cigarettes smoked per day and increasing weight. This suggests not only that gender and tobacco smoking, in particular, are important predictors of plasma vitamin C levels but also that their effects are consistent throughout the developed world.

Adult↗
PubMed1996

An apparent lack of association between Helicobacter pylori infection and risk of gastric cancer in China.

Several prospective studies have shown a significant association between Helicobacter pylori seropositivity and the risk of gastric cancer. Only a small proportion of H. pylori-infected individuals will, however, develop gastric cancer, and it is unclear what effects other factors, such as diet, might have on the risk of cancer. Eighty-seven subjects with gastric cancer were identified during the first 6 years of follow-up (mean 2.4 years) of a cohort of middle-aged men from Shanghai, China. They were matched with 261 cancer-free controls, and serum samples from all subjects, obtained at recruitment, were assayed for anti-H. pylori IgG antibodies. Questionnaire data provided information on a wide range of socio-demographic life-style and dietary variables. H. pylori seropositivity rates in the cases and controls were 54% and 56%, respectively. Neither the overall risk of developing gastric cancer nor the risk of developing non-cardia gastric cancer was significantly associated with prior M. pylori seropositivity. Adjustment for any of the other medical, dietary or life-style variables studied had little effect on the risk of developing non-cardia gastric cancer; simultaneous adjustment for all of these factors yielded an odds ratio of 1.17. The results do not support the hypothesis that H. pylori plays a role in the process of gastric carcinogenesis in China. It is possible that this is an artefact resulting from the relatively short follow-up period to date.

Antibodies, Bacterial↗
PubMed1996

Is Helicobacter pylori transmitted from cats to humans?

BACKGROUND: Subsequent to the isolation of Helicobacter pylori from domestic cats, it has been suggested that the organism might be transmitted from cats to humans. This hypothesis has already gained considerable media attention. MATERIALS AND METHODS: In a previous study of risk factors for H. pylori infection, 447 factory workers from Stoke on Trent in the UK had provided blood samples for H. pylori serological workup. They had also completed a detailed questionnaire concerning their living conditions, including the possession of any household pets, in childhood. Logistic regression was used to assess the association between cat ownership in childhood and H. pylori seropositivity. RESULTS: After adjustment for potential confounders, it was found that subjects who had owned a pet as a child were slightly more likely to be H. pylori seropositive than subjects who had not. There was, however, no difference between subjects who had owned a cat and those with other pets. CONCLUSIONS: These data do not support the hypothesis that H. pylori infection might be transmitted from cats to humans.

Adolescent↗
PubMed1996

Helicobacter pylori transmission: evidence from a comparison with hepatitis A virus.

OBJECTIVE: To assess the possibility that faecal-oral contact might play a role in the transmission of Helicobacter pylori. DESIGN: A cross-sectional comparison of the patterns of hepatitis A and H. pylori seropositivity. METHODS: At interview, blood samples and questionnaire data were collected from a group of 467 male volunteers, aged 18-65, from Stoke-on-Trent, UK. Serum samples from each subject were then analysed for anti-H. pylori and anti-hepatitis A antibodies. RESULTS: Overall, 100 of 175 H. pylori seropositive subjects (57.1%) and 113 of 292 H. pylori seronegative subjects (38.7%) were hepatitis A seropositive (chi 2 = 15.0, P < 0.001). This difference was not statistically significant after adjustment for age group and father's occupation, as a surrogate for socioeconomic status in childhood (P = 0.15). The seroprevalence of hepatitis A increased with age at a rate of 2.3% per year, compared to only 1.0% per year for H. pylori (P = 0.015). CONCLUSION: These data suggest that the case for faecal-oral transmission of H. pylori, in a manner similar to the spread of hepatitis A, is not proven and that other modes of transmission, for instance through oral-oral contact, should also be considered.

Adult↗
PubMed1995

Helicobacter pylori as a risk factor for cancer.

In 1985, gastric cancer was the second most common cause of cancer death in the world. The rapid decline in gastric cancer rates over the last few decades has been attributed to a decline in the prevalence of environmental risk factors for gastric cancer and/or an increase in the prevalence of protective factors. One such risk factor could be the bacterium Helicobacter pylori. Epidemiological studies have shown that areas with high gastric cancer rates often have a correspondingly high prevalence of H. pylori and prospective studies have shown that subjects with serological evidence of H. pylori infection were significantly more likely to go on to develop gastric cancer than those who did not. Helicobacter pylori itself does not appear to be either genotoxic or mutagenic. Infection is, however, associated with increased cell turnover, a chronic immune response accompanied by increased levels of reactive oxygen metabolites and a reduction in gastric levels of ascorbic acid, all conditions that could favour the development of cancer. Nonetheless, the majority of those who are infected with H. pylori do not go on to develop gastric cancer and other factors, such as the strain of the infecting organism or consumption of dietary antioxidants including vitamin C, could also affect the risk of cancer. Finally, it has been estimated that more than one third, and possibly as many as 90% of gastric cancers might be attributable to infection with H. pylori. Prevention and treatment of infection are, therefore, possible approaches to reducing gastric cancer rates. It is, however, unclear what, if any, effect eradication of the infection would have on an individual's risk of gastric cancer and, to date, anti-Helicobacter therapy has only been shown to be of potential benefit in the treatment of low grade gastric MALT lymphomas.

Chronic Disease↗
PubMed1994

Relation between infection with Helicobacter pylori and living conditions in childhood: evidence for person to person transmission in early life.

OBJECTIVES: To relate the prevalence of infection with Helicobacter pylori in adults to their living conditions in childhood to identify risk factors for infection. DESIGN: Prevalence study of IgG antibodies to H pylori (> 10 micrograms IgG/ml, determined by enzyme linked immunosorbent assay (ELISA)) and reported living conditions and other socioeconomic factors in childhood. SETTING: Three factories in Stoke on Trent. SUBJECTS: 471 male volunteers aged 18 to 65 years. MAIN OUTCOME MEASURES: Seroprevalence and variables in childhood. RESULTS: Seroprevalence of H pylori increased with age (22/74 (29.7%) at < 30 years v 29/46 (63%) at 55-65 years; P < 0.001 for trend) and was related to manual occupation (14/65 (21.5%) for non-manual v 162/406 (39.9%) for manual; P = 0.003). After data were adjusted for age and occupation subjects from large families, whose childhood homes were crowded or who regularly shared a bed in childhood, were significantly more likely to be seropositive (adjusted odds ratio (95% confidence interval) 2.15 (1.41 to 3.30) for crowding and 2.13 (1.38 to 3.30) for sharing a bed), but there was no relation with possession of a bathroom, inside toilet, refrigerator, or household pets in childhood. CONCLUSIONS: Close person to person contact in childhood is an important determinant of seroprevalence of H pylori in adulthood, suggesting that the infection is transmitted directly from one person to another and may be commonly acquired in early life.

Adolescent↗
PubMed1994

The absorption and effect of dietary supplementation with omega-3 fatty acids on serum leukotriene B4 in patients with cystic fibrosis.

The substitution of omega-3 (n-3) fatty acids for omega-6 (n-6) fatty acids generates eicosanoids with diminished inflammatory effects. As the lungs of patients with cystic fibrosis (CF) are in a state of chronic inflammation in which increased amounts of eicosanoids are found, n-3 supplementation may reduce this level of inflammation and result in clinical improvement. The absorption and clinical effects of n-3 vs. n-6 fatty acids in CF were measured in a prospective, randomized, double-blind, crossover study in which 14 patients with CF (age: 6-16 years, mean 10.5 years; baseline Shwachman-Brasfield scores: 41-88, mean 76.7) received 6 weeks of n-3 ethyl ester concentrate from menhaden oil (100-131 mg/kg/day, mean 112.8) or n-6 fatty acids from safflower oil (102-132 mg/kg/day, mean 113.3), followed by a washout period of 6 weeks, and then 6 weeks of the other supplement. Analysis by gas chromatography showed that n-3 supplementation resulted in increased eicosapentaenoic acid (20:5n-3) in platelet phospholipids, from 0.14 to 2.16%, P < 0.05 and in increased docosahexaenoic acid (22:6n-3), from 1.33 to 3.72%, P < 0.05. Clinical effects were evaluated at weeks 0, 6, 12, and 18, and analyzed for differences among the n-3, n-6, and washout periods. No adverse effects were reported or observed. No statistically significant differences were found (ANOVA, P > 0.05) in Shwachman-Brasfield scores, sweat test, weight change, or forced expiratory volume and flow (FEV1, FEF25-75%, and FVC) percentiles. Tumor necrosis factor was not measurable in any serum sample. Serum leukotriene B4 (LTB4) levels were significantly reduced by n-3 fatty acids, mean reduction (-177 pg/mL) compared to n-6 fatty acids (+63 pg/mL) P < 0.05. These results show that both n-3 fatty acids are absorbed and incorporated into platelet phospholipids in patients with CF and reduced serum LTB4. No significant clinical differences or adverse effects were found.

Absorption↗
PubMed1994

The epidemiology of low serum pepsinogen A levels and an international association with gastric cancer rates. EUROGAST Study Group.

BACKGROUND/AIMS: Low serum levels of pepsinogen A are indicative of chronic atrophy, a risk factor for gastric cancer. This study investigated the relationships between low pepsinogen A levels, Helicobacter pylori seropositivity, and gastric cancer rates in 17 populations worldwide. METHODS: In each center, about 200 randomly selected subjects (50 male and 50 female, aged 25-34 and 55-64 years) provided serum samples for pepsinogen analysis and H. pylori serology. RESULTS: Cumulative gastric cancer rates were associated with the prevalence of low pepsinogen A levels in men (coefficient, 0.15 [P = 0.06] for mortality; coefficient, 0.36 [P = 0.01] for incidence) but not women. The prevalence of low pepsinogen A levels was also correlated with H. pylori seropositivity in the older age group (r = 0.55; P = 0.02). Low pepsinogen A levels were significantly more common in the older group (7.5% vs. 2.1% in the younger group; P < 0.001), among women (5.5% vs. 4.1% in men; P = 0.04), and among nonsmokers (5.8% vs. 2.9% in current smokers; P = 0.001). CONCLUSIONS: Low pepsinogen A levels are more common in areas with a high seroprevalence of H. pylori and in men in areas with high rates of gastric cancer. The prevalence of low pepsinogen A levels increases with age, but the excess in women and nonsmokers could reflect factors other than gastric pathology.

Adult↗
PubMed1988

Fatal respiratory syncytial virus pneumonitis in a previously healthy child.

Respiratory syncytial virus (RSV) is a cause of significant morbidity and mortality in infants and children with an immunocompromised status or a congenital heart disease. The following case describes a 6 8/12-year-old, previously normal child who had a fatal interstitial pneumonitis caused by RSV. Documentation of RSV as the etiologic agent and documentation of her immune status are presented. In light of recent advances in the rapid diagnosis and treatment of RSV, this virus should be considered in children with an unusual interstitial pneumonitis regardless of their known immunologic status.

Bronchi↗
PubMed1978

Studies on the mitogen responses of germfree allogeneic chimeras. II. Maturation of two cell types and partial restoration of responsiveness of the short-term chimeras.

Germfree allogeneic bone marrow chimeras (ABMC) were produced by the i.v. injection of approximately 10(7) bone marrow cells from germfree DBA/2 mice into lethally irradiated germfree C3H mice. In the germfree state, the short-term ABMC showed no histologic signs of graft-vs-host reactions (GVHR), yet splenic lymphocytes were unable to respond to PHA, Con A, or SRBC. Attempts to remove responsiveness by the implantation of a DBA/2 thymus under the host kidney capsule also resulted in failure. However, when the donor thymus was enclosed in a cell-impermeable chamber to eliminate a GVH reaction, responsiveness to Con A was restored. The PHA and SRBC responses were unaffected by this treatment. Daily injections of thymosin caused both an increased Con A response and increased numbers of PFC, although the PHA response was again unaffected. Thus, soluble substances from thymic tissue can be used to overcome partially the histocompatibility barrier present in the ABMC that affects at least two different functional cell populations.

Animals↗