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Biomedical subjects

D A Warner

Publications and source records attributed to D A Warner.

14 recordsLinked to original sources
PubMed2006

Do operational sex ratios influence sex allocation in viviparous lizards with temperature-dependent sex determination?

Under certain environmental situations, selection may favour the ability of females to adjust the sex ratio of their offspring. Two recent studies have suggested that viviparous scincid lizards can modify the sex ratio of the offspring they produce in response to the operational sex ratio (OSR). Both of the species in question belong to genera that have also recently been shown to exhibit temperature-dependent sex determination (TSD). Here we test whether pregnant montane water skinks (Eulamprus tympanum) utilise TSD to select offspring sex in response to population wide imbalances in the OSR, by means of active thermoregulation. We use a combination of laboratory and field-based experiments, and conduct the first field-based test of this hypothesis by maintaining females in outdoor enclosures of varying OSR treatments throughout pregnancy. Although maternal body temperature during pregnancy was influenced by OSR, the variation in temperature was not great enough to affect litter sex ratios or any other phenotypic traits of the offspring.

Animals↗
PubMed1989

Effects of Polyploidy on Photosynthetic Rates, Photosynthetic Enzymes, Contents of DNA, Chlorophyll, and Sizes and Numbers of Photosynthetic Cells in the C(4) Dicot Atriplex confertifolia.

Photosynthetic rates, chlorophyll content, and activities of several photosynthetic enzymes were determined per cell, per unit DNA, and per unit leaf area in five ploidal levels of the C(4) dicot Atriplex confertifolia. Volumes of bundle sheath and mesophyll protoplasts were measured in enzymatic digestions of leaf tissue. Photosynthetic rates per cell, contents of DNA per cell, and activities of the bundle sheath enzymes ribulose 1,5-bisphosphate carboxylase (RuBPC) and NAD-malic enzyme per cell were correlated with ploidal level at 99% or 95% confidence levels, and the results suggested a near proportional relationship between gene dosage and gene products. There was also a high correlation between volume of mesophyll and bundle sheath cells and the ploidal level. Contents of DNA per cell, activity of RuBPC per cell, and volumes of cells were correlated with photosynthetic rate per cell at the 95% confidence level. The mesophyll cells did not respond to changes in ploidy like the bundle sheath cells. In the mesophyll cells the chlorophyll content per cell was constant at different ploidal levels, there was less increase in cell volume than in bundle sheath cells with an increase in ploidy, and there was not a significant correlation (at 95% level) of phosphoenolpyruvate carboxylase activity or content and pyruvate,Pi dikinase activity with increase in ploidy. The number of photosynthetic cells per unit leaf area progressively decreased with increasing ploidy from diploid to hexaploid, but thereafter remained constant in octaploid and decaploid plants. Numbers of cells per leaf area were not correlated with cell volumes. The mean photosynthetic rates per unit leaf area were lowest in the diploid, similar in 4x, 6x, and 8x, and highest in the decaploid. The photosynthetic rate per leaf area was highly correlated with the DNA content per leaf area.

Journal Article↗
PubMed1988

Hepatic hydroxymethylglutaryl coenzyme A reductase activity in inbred strains of mice.

Hydroxymethylglutaryl coenzyme A reductase (HMGR) activity is a major factor in the regulation of cholesterol homeostasis. Enzyme activity is known to vary with age, sex, diurnal cycle, and dietary properties in rats. Mice are available in numerous genetic strains and could be a useful inexpensive animal model for studying diet and genetic interactions in the regulation of cholesterol metabolism. Obese and non-obese C57BL/6J, CBA/J, and obese and non-obese DW dbPas mice were subjected to variations in light cycle, feeding schedule, and pectin and fat composition of their diets. They were then killed by decapitation, and hepatic microsomal HMGR analyzed. The mice responded in the same ways as rats to light cycle, feeding pattern, and sex difference. They exhibited marked differences in HMGR activity due to age, genotype, strain, and diet variations. We conclude that mice will, indeed, offer an excellent animal model for the study of cholesterol metabolism regulation.

Animals↗
PubMed1987

Photosynthesis, Leaf Anatomy, and Cellular Constituents in the Polyploid C(4) Grass Panicum virgatum.

Photosynthetic gas exchange, activities of six key C(4) cycle enzymes, amounts of soluble protein, chlorophyll, and DNA, and various leaf anatomical and structural features were measured in naturally occurring tetraploid and octaploid plants of the NAD-malic enzyme type C(4) grass Panicum virgatum L. On a leaf area basis, the photosynthetic rate and concentrations of DNA, soluble protein, and chlorophyll were 40 to 50% higher, and enzyme activities 20 to 70% higher in the octaploid than in the tetraploid. Photosynthetic cells in the octaploid were only 17 to 19% larger in volume, yet contained 33 to 38% more chloroplasts than cells in the tetraploid. On a per cell basis the contents of DNA, soluble protein, and chlorophyll, activities of carboxylating photosynthetic enzymes, and carbon assimilation rate were all doubled in octaploid compared with tetraploid cells. Since cellular volume did not double with genome doubling, cellular constituents were more concentrated in the cells of the octaploid. The influences of polyploidy were balanced between mesophyll and bundle sheath cells since the changes in physical and biochemical parameters with ploidy level were similar in both cell types. We conclude that photosynthetic activity in these two polyploid genotypes of P. virgatum is determined by enzyme activities and concentrations of biochemical constituents, and that selection for smaller cell volume has led to higher photosynthetic rates per unit leaf area in the octaploid. The ratio of DNA content to cellular volume is a major factor determining the concentrations of gene products in cells. The number of chloroplasts, however, is controlled more by cellular volume than by the number of nuclear chromosomes.

Journal Article↗
PubMed1985

Semantic processing and serial learning by EMR adolescents.

In a previous study we found that providing the semantic strategy of stories linking to-be-remembered items facilitated free-recall in original learning and in retention after 2 months (Glidden & Warner, 1983). The present study replicated the previous study but with a serial-recall requirement. A story linking items within blocks of a to-be-recalled list was provided for EMR subjects. In comparison to control subjects, they recalled more in the early trials of original learning, but retention after 8 months was comparable for the two conditions. Future investigators should focus on how to train retarded subjects to generate their own semantic strategies for serial learning.

Adolescent↗
PubMed1983

Semantic processing can facilitate free recall in mildly retarded adolescents.

The efficacy of semantic processing in free recall was investigated in two experiments with EMR adolescents. In Experiment 1, they were taught to use one of two semantic strategies for memorizing a 15-word list. Compared with controls, neither strategy helped recall either in original learning or transfer. In Experiment 2, one of the semantic strategies, a story mnemonic, was investigated further. Rather than being taught to construct their own stories as in Experiment 1, subjects in Experiment 2 were provided with experimenter-composed stories. They showed better immediate recall and retention after 2 months than did no-strategy controls. However, about 1 year after original learning, the retention of experimental and control subjects no longer differed. Discussion focused on the story mnemonic's potential utility and the criteria for judging such potential, e.g., amount of facilitation, ease of training and performance of the strategy, and the degree of its generalizability.

Adolescent↗
PubMed1983

Semantic processing and recall improvement of EMR adolescents.

Semantic processing, in the form of stories linking to-be-remembered words, was compared with cumulative rehearsal in a free-recall task. Educable mentally retarded adolescents were either taught to generate a story, provided with a story, taught to rehearse cumulatively, or assigned to no-strategy control groups. Semantic-processing subjects showed better recall at original learning and, to a lesser extent, at a 20-week retention test. Results were discussed with reference to the mechanism of recall improvement and the generalizability of semantic training to a diversity of tasks.

Adolescent↗
PubMed1982

Research on imitation in mentally retarded persons: theory-bound or ecological validity run amuck?

Research on imitation in mentally retarded persons was examined to assess whether the bulk of the research had been aimed at theory confirmation and/or was ecologically valid. Sixty-seven studies, mostly published between 1975 and 1980, were reviewed within the framework of the Yando, Seitz, and Zigler (1978) two-factor developmental theory of imitation. It was concluded that most of the research on imitation in mentally retarded persons was not theoretical, but was ecologically valid. The failure of a dominant theoretical framework has led to a lack of systematic and programmatic effort, thus hampering the applied potential of modeling and imitation in the education and training of mentally retarded individuals.

Cognition↗
PubMedDate not supplied

Infant ventilation and oxygenation by basic life support providers: comparison of methods.

INTRODUCTION: Little information is available in the performance of infant ventilation by basic life support (BLS) personnel. HYPOTHESIS: There are no significant differences between mouth-to-mouth (M-M), mouth-to-mask (M-Ma), pediatric bag-mask (PBM), and adult bag-mask (ABM) devices in the percent of acceptable breaths delivered by BLS providers. METHODS: Fifty certified BLS providers performed five ventilation methods in random sequences for 60 seconds each on a 5kg infant mannequin following standardized instructions. Supplemental oxygen, 10 l/min, was supplied with one M-Ma trial and PBM methods. Airway patency, peak airway pressure (PAP), ventilatory rate (VR), tidal volume, and delivered oxygen concentration (FiO 2) were recorded. The percent of breaths with excessive PAP (i.e., greater than 30 mmHg), percent of acceptable breaths using loose (i.e., 25-125ml) and strict (i.e., 50-100ml) criteria, and FiO 2 at 15, 30, 45, and 60 seconds were compared between ventilation methods using ANOVA. RESULTS: For all subjects and those with a patent airway (n=36), there were no significant differences in the percentage of acceptable breaths produced by PBM (56+/-6) (mean+/-SEM; all subjects) and ABM (41+/-6.2) was significantly greater than M-Ma, with and without a patent airway. Although RR and the percentage of excessive breaths were not significantly different, the percentage of acceptable breaths and FiO 2 delivered with each ventilation method was significantly better in the patent airway group.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗