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Biomedical subjects

D Barclay

Publications and source records attributed to D Barclay.

12 recordsLinked to original sources
PubMed1995

Health-related behaviors of survivors of childhood cancer.

The health-related beliefs and behaviors of long-term survivors of childhood cancer are important because of vulnerability to adverse late effects from their primary malignancy and its therapy. A health behavior survey was completed by 110 parents of long-term survivors ranging in age from 11-17 years, and by 40 adult long-term survivors of childhood cancer ranging in age from 18-29 years. The survey included questions on the former patient's frequency of alcohol and tobacco use, as well as diet, exercise, sleep, dental, and seatbelt habits. The reported prevalence of tobacco and alcohol use was less than 10% among those less than 18 years old. Among the adults, tobacco (17.5%) and alcohol (72.5%) use was greater, but problem drinking was infrequently reported. In order to assess their perceived vulnerability, we asked the parents and the young adult patients to rate the strength of their belief that it is more important for the patient to keep healthy compared to most other children or young adults. Contrary to our expectation, demographic factors such as the patient's gender, socioeconomic level, or time elapsed since completion of therapy exerted minimal influence on their responses. Over 80% of parents and 60% of young adult survivors believed that it was more important for the former patient to remain healthy compared to most other people. However, this shared belief in increased vulnerability was inconsistently expressed in the patient's health behaviors. These results suggest that specific changes are needed in the health assessment and education of long-term survivors of childhood cancer.

Adolescent↗
PubMed1995

A hybrid likelihood algorithm for risk modelling.

The risk of radiation-induced cancer is assessed through the follow-up of large cohorts, such as atomic bomb survivors or underground miners who have been occupationally exposed to radon and its decay products. The models relate to the dose, age and time dependence of the excess tumour rates, and they contain parameters that are estimated in terms of maximum likelihood computations. The computations are performed with the software package EPI-CURE, which contains the two main options of person-by person regression or of Poisson regression with grouped data. The Poisson regression is most frequently employed, but there are certain models that require an excessive number of cells when grouped data are used. One example involves computations that account explicitly for the temporal distribution of continuous exposures, as they occur with underground miners. In past work such models had to be approximated, but it is shown here that they can be treated explicitly in a suitably reformulated person-by person computation of the likelihood. The algorithm uses the familiar partitioning of the log-likelihood into two terms, L1 and L0. The first term, L1, represents the contribution of the 'events' (tumours). It needs to be evaluated in the usual way, but constitutes no computational problem. The second term, L0, represents the event-free periods of observation. It is, in its usual form, unmanageable for large cohorts. However, it can be reduced to a simple form, in which the number of computational steps is independent of cohort size. The method requires less computing time and computer memory, but more importantly it leads to more stable numerical results by obviating the need for grouping the data. The algorithm may be most relevant to radiation risk modelling, but it can facilitate the modelling of failure-time data in general.

Algorithms↗
PubMed1994

Probability of causation for lung cancer after exposure to radon progeny: a comparison of models and data.

The estimates of lung cancer risk due to the exposure to radon decay products are based on different data sets from underground mining and on different mathematical models that are used to fit the data. Diagrams of the excess relative rate per 100 working level months in its dependence on age at exposure and age attained are shown to be a useful tool to elucidate the influence that is due to the choice of the model, and to assess the differences between the data from the major western cohorts and those from the Czech uranium miners. It is seen that the influence of the choice of the model is minor compared to the difference between the data sets. The results are used to derive attributable lifetime risks and probabilities of causation for lung cancer following radon progeny exposures.

Adult↗
PubMed1991

Dietary habits and attitudes. Euronut SENECA investigators.

This chapter describes data on dietary behaviour collected from 2586 elderly persons, born between 1913 and 1918 and living in 19 towns from 12 European countries, who participated in the Euronut SENECA Study on Nutrition of the Elderly in Europe. Groups of elderly subjects with particular dietary habits were identified. They included those persons having low or high meal frequencies, those not having regular cooked meals, those consuming home-produced foods, those having special interest or awareness in nutrition, those eating alone and those with food-budgeting problems. In future analyses, we shall endeavour to determine whether the dietary intake, nutritional status and health of these groups are related to their dietary habits.

Aged↗
PubMed1990

Prevalence and serotype specificity of rotavirus antibodies in different age groups of Ecuadorian infants.

The age-specific prevalence of antibody to rotavirus was studied in 1404 Ecuadorian children enrolled in a national nutrition and health survey. ELISA and neutralizing antibody analysis showed evidence for primary rotavirus infection in 6- to 12-month-old children, who showed also a more-than-threefold increase in significant diarrheal episodes in comparison with infants less than 6 months old. At this age, 56% of the sera with neutralizing antibody were monospecific. With increasing age a gradual decrease in prevalence of monospecific sera, to 10% in 5-year-old children, was observed. Monospecific sera were directed in decreasing frequency against serotypes 4 (56%), 3 (20%), 2 (14%), and 1 (10%). Serotype 4-specific antibody was acquired at an earlier age than were antibodies to the other serotypes, and 91% of sera with dual specificity neutralized serotype 4, whereas only 2% of sera that neutralized three serotypes failed to neutralize serotype 4.

Acute Disease↗
PubMed1990

Age-specific prevalence of antibody to enterotoxigenic Escherichia coli in Ecuadorian and German children.

Serum samples from 1397 Ecuadorian children 0-5 years of age were tested by ELISA for antibodies to enterotoxigenic Escherichia coli (ETEC). A gradual prevalence and titer increase was seen for IgG antibodies to heat-labile enterotoxin in children 6-18 months old; 90% prevalences were reached in the second year of life. At this age less than 10% of West German children showed IgG antibodies to heat-labile enterotoxin. In Ecuador age-related ETEC-specific antibody titer increases correlated with age-related prevalence of diarrheal disease. On the other hand, pooled lipopolysaccharide from different ETEC-associated O serogroups could not be used as a seroepidemiologic marker of ETEC infections.

Age Factors↗
PubMed1986

Interrelations between structure and function in the vocal repertoire of Saimiri. Asking the monkeys themselves where to split and where to lump.

The identification of units used in primate vocal behaviour and the isolation of components essential for intraspecific communication (i.e. having a function) from possibly inessential ones (i.e. having no function) is an absolute prerequisite to a successful analysis of primate vocalizations. For most calls special methods are required because neither the essentials of structure nor their relation to function are known, nor the context involved. For calls without any distinct frequency modulation we showed that the animals utter calls containing categorical amplitude changes. The changes within one call are either very small or very large. The positions or the very large amplitude changes within a call depend on the social situation the animals were subjected to and affect the immediately succeeding vocalization of the conspecific. This proves that in vocal communication discrete components are produced (structure) as well as used (function).

Animal Communication↗
PubMed1986

Nutritional significance of alterations in serum amino acid patterns in goitrous patients.

Twenty-nine amino acids were analyzed in the sera of 105 adult Senegambian goitrous patients classified as stages I, II, and III according to World Health Organization recommendations. Mean serum concentration of all essential amino acids revealed highly significant drops (p less than 0.001) as goiter stage increased, except for methionine (Met). Most nonessential amino acids (NEAA) and intermediary metabolites were similarly characterized by a general decrease to the subnormal range, although some resisted depression in stages II and III. Homocystine (Hcy) demonstrated a unique pattern in that it was the only NEAA distinguished by regularly rising serum levels. These data are consistent with the view that endemic goiter is associated with overall stepwise downregulation in protein metabolism. In addition to iodine restriction, generalized malnutrition may aggravate the goitrogenic processes. Serum levels of Met and Hcy strongly suggest that the first step of the transsulfuration pathway is impaired in protein-depleted states due to cystathionine beta-synthase (EC 4.2.1.22) deficiency.

Adult↗
PubMed1983

Amino acid-enriched plasteins: a source of limiting amino acids for the weanling rat.

The biological availability to the weanling rat of two amino acid-enriched plasteins, tryptophan and methionine plastein, was tested. In both experiments rats were fed diets containing graded levels of the amino acid either in the free form or as the amino acid-enriched plastein. The first experiment tested the utilization of tryptophan plastein. The results as indicated by weight gain, food intake and plasma levels of tryptophan showed that the tryptophan in the plastein was utilized to the same extent as the free amino acid. Brain tryptophan levels correlated better with plasma Trp:neutral amino acid ratios (r = 0.83) than with plasma tryptophan itself (r = 0.63) suggesting that the small changes observed in plasma amino acid profiles were responsible for differences in the brain tryptophan concentrations among the L-tryptophan and tryptophan plastein groups. In the second experiment, utilization of methionine plastein was tested. Based on weight gain and food intake data, it was concluded that methionine plastein was also utilized to the same extent as free L-methionine.

Amino Acids↗