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Biomedical subjects

D M Bryant

Publications and source records attributed to D M Bryant.

17 recordsLinked to original sources
PubMed2004

Variation in temperature increases the cost of living in birds.

The effect of temperature variability on laying birds was studied experimentally, using Japanese quail. Two aspects of temperature variability were investigated: the effects of regular daily variation in temperature, and of a sudden change in temperature. Both of these may become more common as a consequence of climate change. These manipulations were carried out at two levels of food supply. Energy expenditure increased with higher daily temperature variation, and also after a sudden change in temperature, taking several days to settle to a constant level. Manipulating daily temperature variation also resulted in smaller eggs being laid under more variable temperatures, when food quality was also low. The results demonstrate that day-to-day variation in temperature, as well as mean temperature, affects energy expenditure, which can have consequences for egg production.

Animals↗
PubMed2002

State-dependent behaviour in breeding barn swallows (Hirundo rustica): consequences for reproductive effort.

Life-history theory offers an explanation for the intraspecific variation in reproductive effort; increased levels of current reproductive success, for example, may trade off against residual reproductive value. Even where such trade-offs have been demonstrated, however, much variation in effort remains unexplained and the underlying causes are usually obscure. We examined body state, i.e. energy reserves, as a factor, which could moderate reproductive effort. Specifically, overnight heating and cooling treatments were used to adjust dawn energy reserves in female swallows attending their nests without impinging on the opportunities for foraging. Changes in reproductive effort were measured as 'daytime energy expenditure' (doubly labelled water technique) and the 'number of feeding visits' during brood rearing, which both relate positively to current reproductive success. Our experimental treatments and responses were then compared using the common currency of energy. In response to positive and negative state manipulations, female swallows increased and decreased, respectively, their daytime energy expenditure (and number of feeding visits). These responses to experimental manipulation of state provided evidence of a direct link between the energy expenditure, life history and behaviour, which has hitherto proved elusive. They allow that energy supply and expenditure play a regulatory role in reproductive effort, and indicate that units of energy expenditure probably carry fitness costs and benefits, which are context dependent.

Animals↗
PubMed2001

Testosterone influences basal metabolic rate in male house sparrows: a new cost of dominance signalling?

Sexually selected signals of individual dominance have profound effects on access to resources, mate choice and gene flow. However, why such signals should honestly reflect individual quality is poorly understood. Many such signals are known to develop under the influence of testosterone. We conducted an experiment in male house sparrows in which testosterone was manipulated independently during two periods: before the onset of the breeding season and prior to the autumn moult. We then measured the effects of these manipulations on basal metabolic rate and on the size of the chest bib, a sexually selected signal. The results demonstrate that testosterone simultaneously affects both signal development and basal metabolic rate in the house sparrow (Passer domesticus). This evidence, therefore, supports a novel conclusion: that testosterone-dependent signals act as honest indicators of male quality possibly because only high-quality individuals can sustain the energetic costs associated with signal development.

Animals↗
PubMed2000

The energetic cost of short flights in birds.

Many small birds perform short flights, for which take-offs, ascents and descents form a large component of the total flight time and which are characterised by low airspeeds. Using the doubly-labelled water technique, zebra finches Taeniopygia guttata engaging in repeated short flights were found to expend 13.65 kJ more than 'non-flying' controls, which equated to a flight expenditure of 27.8 times their basal metabolic rate. This is over three times the predicted flight expenditure derived from existing aerodynamic models. These data were used to determine a coefficient (0.11) for converting the mechanical power derived from aerodynamic models into metabolic power. An equation is presented, based on body mass, which can be used to predict the costs of short flights in ecological and behavioural studies of birds.

Animals↗
PubMed1996

Quality of center child care and infant cognitive and language development.

The relations between quality of center-based child care and infant cognitive and language development were examined in a sample of 79 African-American 12-month-old infants. Both structural and process measures of quality of child care were collected through interviews with the center director and observation of the infant classroom. Results indicated that quality of infant care positively correlated with scores on standardized assessments of cognitive development (Bayley Scales of Infant Development), language development (Sequenced Inventory of Communication Development), and communication skills (Communication and Symbolic Behavior Scales). In addition, quality of care in child care centers and at home was positively related. Analyses that adjusted for this association between quality of care at home and in child care suggested that the process measure of quality of child care independently related to the infant's cognitive development, and one structural measure, the infant-adult ratio, independently related to the infant's overall communication skills. Neither child nor family factors was found to moderate the association between child care quality and infant development. These findings, in conjunction with the growing child care literature, suggest that researchers and policymakers should focus on how quality of child care can be improved to enhance, not impair, infant development.

Black or African American↗
PubMed1992

Infant Health and Development Program for low birth weight, premature infants: program elements, family participation, and child intelligence.

The Infant Health and Development Program was an eight-site randomized controlled trial testing the efficacy of early intervention to enhance the cognitive, behavioral, and health status of low birth weight, premature infants. The 377 intervention families received for the first 3 years of life: (1) pediatric follow-up, (2) home visits, (3) parent support groups, and (4) a systematic educational program provided in specialized child development centers. The control group (n = 608) received the same pediatric follow-up and referral services only. This paper describes the delivery of the intervention and its outcomes. A Family Participation Index that was the sum of participation frequencies in each of the program modalities unique to the intervention revealed that program implementation was not different across the eight sites. Index scores did not vary systematically with mother's ethnicity, age, or education or with child's birth weight, gender, or neonatal health status; but they were positively related to children's IQ scores at age 3. Only 1.9% of children of families in the highest tercile of participation scored in the mentally retarded range (IQ less than or equal to 70), whereas 3.5% and 13% of children in the middle and lowest participation terciles, respectively, scored in the retarded range. Similar findings were obtained for borderline intellectual functioning. These findings are consistent with previous research linking intensity of intervention services with degree of positive cognitive outcomes for high-risk infants. The determinants of variations in individual family participation remain unknown.

Child Day Care Centers↗
PubMed1990

A longitudinal study of two early intervention strategies: Project CARE.

65 families with children at risk for cognitive difficulties were randomly assigned at the time of the child's birth to 1 of 3 groups, 2 intervention and 1 control. For the most intensive intervention group, family education was combined with a center-based educational day-care program; the less intensive intervention group received the home-based family education program only. To assess the cognitive performance of children, The Bayley Scales of Infant Development were administered at 6, 12, and 18 months; the Stanford-Binet Intelligence Test at 24, 36, and 48 months; and the McCarthy Scales of Children's Abilities at 30, 42, and 54 months. On each test after the 6-month assessment, scores of children in the educational day-care plus family support group were greater than those in the other 2 groups. No cognitive intervention effects were obtained for the family education group. Group effects were not obtained for measures of either the quality of the home environment or parent attention.

Child Day Care Centers↗
PubMed1990

Early intervention: why, for whom, how, and at what cost?

When the concept of intervention is applied to human development, the goal is usually to enhance functioning or to prevent some unwanted condition. During the past 20 years, the United States has committed itself to an early intervention position for young children who are socio-economically, educationally, or physically disadvantaged. This article summarizes the knowledge base concerning early educational interventions and to recommend actions concerning public policy and associated research.

Child Development↗
PubMed1990

Double-blind placebo-controlled study of nortriptyline in depressed adolescents using a "fixed plasma level" design.

We performed a random assignment, double-blind, placebo-controlled study of nortriptyline (NT) in postpubertal 12- to 17-year-olds with Research Diagnostic Criteria (RDC) and DSM-III major depressive disorder. The protocol included a 2-week placebo washout phase and an 8-week double-blind, placebo-controlled phase with weekly plasma level monitoring. Active subjects had their plasma level placed at 80 +/- 20 ng/ml by using previously developed tables to determine the starting dose from a plasma level drawn 24 hours after a single dose administered at baseline. The study population was severely depressed and had a chronic, unremitting course prior to study; a high percentage of family histories with affective disorder, alcoholism, and suicidality; and a high rate of comorbidity. Of the 52 subjects enrolled, there were 17 placebo washout responders, 4 dropouts, and 31 completers (12 active and 19 placebo). Only one active subject responded; therefore, the study was terminated early. The mean NT plasma level was 91.1 (18.3 SD) ng/ml. The two treatment groups had similar postprotocol severity ratings. Subjects on active drug did not evidence the anticholinergic side effects reported in adult samples. The negative outcome in this study is similar to the findings in our previously reported NT study in prepubertal 6- to 12-year-olds.

Adolescent↗
PubMed1989

Language skills of children with different preschool experiences.

This study examined the language at age 5 of socioeconomically disadvantaged children who had been randomly assigned at birth to a language-enriched day care program with a parent education component, a parent education program without a language-enriched day care, or no treatment. The interventions were administered between the ages of 3 months to 5 years. Language measures, reflecting children's ability to manipulate topics, as well as their structural complexity, semantic diversity, and general talkativeness were examined. The results showed that the disadvantaged children who attended the language-enriched day care program with the parent education component used a significantly greater proportion of high quality topic manipulation skills and less low quality topic manipulation skills during conversation than did children in the other two groups. The day care effect on high quality topic manipulation was present even after adjusting for children's intelligence and for the amount of community day care experience of the children in the parent education alone and control groups. No significant treatment differences were found for structural, semantic, and talkativeness measures. Implications of the result for early language intervention are discussed.

Child Day Care Centers↗
PubMed1982

Primary prevention of developmental retardation during infancy.

This review examines eighteen exemplary prevention-oriented early intervention programs designed for high-risk and normal infants. The target populations, the form of the program delivery, and the content of the curriculum are described. Issues in the design and methodology of such programs are discussed. The review also summarizes continuing and delayed effects of early intervention programs with an emphasis on those projects that had a follow-up evaluation phase. Finally, three theoretical perspectives are presented. These perspectives have important implications for infant program planning and evaluation from which recommendations are made for future programs designed for high-risk infants.

Child↗
PubMed1975

Relationships between dietary and plasma concentrations of calcium and phosphorus in intact and ultimobranchialectomized chickens.

Two experiments were conducted with cockerels to determine whether the presence or absence of the ultimobranchial glands would influence the relationship between dietary and plasma calcium and phosphorus. Broiler type cockerels, 16 weeks of age which had been sham operated (SHAM) or ultimobranchialectomized (UBX) 1 to 3 weeks earlier, were fed diets containing 0.8 or 2.4% calcium and 0.13 to 0.33% phosphorus. The SHAM cockerels fed diets containing 0.8% Ca and 0.13% P did not develop hypercalcemia whereas the UBX cockerels fed this diet developed slight significant hypercalcemia after 17 to 21 days. In Experiment I, SHAM cockerels fed the diet containing 2.4% Ca and 0.13% P developed mild, chronic hypercalcemia (12.7 mg./100 ml.) with a plasma phosphorus of 3.03 mg. P/100 ml., whereas the UBX cockerels fed the same diet developed severe hypercalcemia (16.0 mg./100 ml.) and hypophosphatemia, 1.68 mg. P/100 ml. In Experiment 2 the following plasma values were observed after 17 days of consuming the experimental diets: SHAM fed 2.4% Ca and 0.13% P had 10.6 mg. Ca/100 ml. and 3.59 mg. P/100 ml., whereas UBX fed the same diet had 12.8 mg. Ca/100 ml. and 2.24 mg. P/100 ml. The UBX fed 2.4% Ca and 0.33% P for 17 days had plasma values of 10.8 mg. Ca/100 ml. and 4.48 mg. P/100 ml. It is concluded that the presence of the ultimobrancial glands are essential to the regulation of plasma calcium and phosphorus in chickens which consume high calcium-low phosphorus diets.

Animals↗