Branch Width and Height Influence the Incorporation of Branches into Foraging Trails and Travel Speed in Leafcutter Ants Atta cephalotes (L.) (Hymenoptera: Formicidae).

Fallen branches are often incorporated into Atta cephalotes (L.) foraging trails to optimize leaf tissue transport rates and economize trail maintenance. Recent studies in lowlands show laden A. cephalotes travel faster across fallen branches than on ground, but more slowly ascending or descending a branch. The latter is likely because (1) it is difficult to travel up or downhill and (2) bottlenecks occur when branches are narrower than preceding trail. Hence, both branch height and width should determine whether branches decrease net travel times, but no study has evaluated it yet. Laden A. cephalotes were timed in relation to branch width and height across segments preceding, accessing, across, and departing a fallen branch in the highlands of Costa Rica. Ants traveled faster on branches than on cleared segments of trunk-trail, but accelerated when ascending or descending the branch-likely because of the absence of bottlenecks during the day in the highlands. Branch size did not affect ant speed in observed branches; the majority of which (22/24) varied from 11 to 120 mm in both height and width (average 66 mm in both cases). To determine whether ants exclude branches outside this range, ants were offered the choice between branches within this range and branches that were taller/wider than 120 mm. Ants strongly preferred the former. Our results indicate that A. cephalotes can adjust their speed to compensate for the difficulty of traveling on branch slopes. More generally, branch size should be considered when studying ant foraging efficiency.

The genealogy of British Poultry Science.

The first issue of British Poultry Science was published in April 1960. In this paper the origin and development of the Journal and the organisations with which it has been associated are traced.

Glycemic index, cholecystokinin, satiety and disinhibition: is there an unappreciated paradox for overweight women?

BACKGROUND: The clinical utility of a low glycemic index (LGI) diet for appetite and food intake control is controversial. Complicating the issue are psychological and behavioral influences related to eating. OBJECTIVE: The aim of this study was to investigate the satiety and glycemic response to high GI (HGI) and LGI meals in overweight restrained (R, n=12) and unrestrained (UR, n=10) women. DESIGN AND MEASUREMENTS: In a randomized crossover study, subjective satiety, cholecystokinin (CCK), glucose, insulin, triacylglyceride (TG) and free fatty acids (FFAs) were measured at defined intervals for 8 h after the participants consumed HGI or LGI test meals. Test meals were matched for energy, energy density, macronutrient content and available carbohydrate, but differed by carbohydrate source; refined grain versus whole grain, respectively. RESULTS: The HGI meal resulted in greater satiety overall, suppressing hunger, desire to eat and prospective consumption compared with the LGI (P<0.01) meal. Plasma CCK was significantly elevated after the HGI meal compared with the LGI meal (P<0.001). Plasma glucose, insulin and TG were higher and FFAs were lower after the HGI meal compared with the LGI meal (P<0001). Dietary restraint did not significantly influence CCK (P=0.14) or subjective satiety (P>0.4); however, an interaction of restraint and disinhibition on CCK was apparent. CCK was blunted in R participants with higher disinhibition scores than UR or R participants with lower disinhibition scores (P<0.05). CONCLUSIONS: A LGI diet may not be suitable for optimal satiety and appetite control in overweight women. The relationship between cognitive influences of eating and biobehavioral outcomes requires further investigation.

Periventricular leukomalacia: relationship between lateral ventricular volume on brain MR images and severity of cognitive and motor impairment.

PURPOSE: To evaluate the utility of lateral ventricular volume measurements in predicting motor and cognitive impairment severity in children with periventricular leukomalacia (PVL), with or without seizures. MATERIALS AND METHODS: The charts of children with spastic cerebral palsy and PVL documented on brain magnetic resonance (MR) images were reviewed. Affected children were grouped by motor and cognitive impairment severity and seizure disorder. An age-matched control group was established. Lateral ventricular volumes were measured on two-dimensional T2-weighted spin-echo MR images. Analysis of variance was used to identify significant differences in mean lateral ventricular volume between groups. Paired analyses of differences were performed with the Bonferroni t method. RESULTS: Thirty-six children (24 boys, 12 girls) with spastic cerebral palsy and PVL and 21 age-matched control subjects (14 boys, seven girls) were identified. Mean lateral ventricular volumes of the moderate and marked motor deficit groups were significantly larger than those of the control and mild motor deficit groups (F = 29.24; alpha = .01). Mean lateral ventricular volumes of all cognitive impairment groups were significantly larger than those of the control and no-cognitive-impairment groups (F = 21.101 alpha = .01). There was no difference in mean lateral ventricular volume between children with PVL with or without seizures. CONCLUSION: Lateral ventricular volume measurements can be used as quantitative markers of clinical impairment severity and as clinical outcome predictors before formal testing is possible.

Genetic transformation of chickens using irradiated male gametes.

Results have been obtained which corroborate those of Pandey and Patchell (Molec. Gen. Genet., 186, 305, 1982) in demonstrating that genetic material from irradiated semen is incorporated into the embryo and expressed, albeit at rather a low rate, and is subsequently transmitted to progeny of the transfected birds. The method provides a technically straightforward means of transferring genetic material where rapid and reliable means of detecting the transferred gene exist. An advantage of the method is that regulatory regions are likely to be carried with the transferred gene but there is equally a disadvantage in the simultaneous transfer of unwanted material.

Breeding for disease resistance--the prospective role of genetic manipulation.

Economic considerations have meant that selection for resistance to disease has taken second place to that for productivity traits. Recent developments in genetic manipulation suggest that this may not be necessary in the future because it has become feasible to insert resistance genes into the genome of the fowl without compromising existing productivity traits. This review considers aspects of the genetic manipulation of disease resistance of the fowl, methods available for inserting genes and the identification of genes for insertion. It is concluded that of the technical strategies for inserting genes currently being developed those utilising defective, non-replicating retroviruses are the most promising. Studies to identify genes associated with resistance to disease are only now beginning. Although there has been some research into generalised immunological resistance to disease the results have been disappointing, and it seems likely that the use of specific resistance genes relating to each pathogen will be necessary. In particular the use of complementary or antisense genes to inhibit viral infections seems particularly promising.

Genetic transformation of chickens using irradiated sperm: co-transfer of undesirable genes.

An attempt was made to utilise the recently demonstrated method of gene transfer using irradiated male gametes to transfer the B21 associated resistance to Marek's disease into a susceptible line of chickens. Although none of the 1486 progeny tested showed evidence of the transfer of the B21 haplotype a substantial proportion acquired a second marker, susceptibility to lymphoid leukosis virus. These results confirm and extend previous reports in suggesting that although gene transfer by this method occurs at a relatively high frequency, expression of the transferred genes is variable; whether this reflects properties of the DNA itself or of cellular mechanism of expression is not clear.

Effects of continuous treatment with synthetic ACTH1-24 or corticosterone on immature Gallus domesticus.

Immature chickens were implanted with osmotic pumps filled with ACTH1-24 or pellets consisting of mixtures of cholesterol with corticosterone (0, 10, 20 or 40% by weight). Continuous infusion of ACTH1-24 (2.2 micrograms/hr:120 micrograms/kg body wt/day) caused increases in plasma concentrations of corticosterone, glucose, cholesterol, triglyceride, and uric acid during the first week, and a reduction in weight gain, an increase in the relative weights of the adrenals and liver, and a decrease in the weights of the bursa and spleen. Treatment with pellets containing corticosterone caused dose-related increases in the plasma concentrations of corticosterone, glucose, triglyceride, and cholesterol, an increase in liver size, and a decrease in the size of the bursa and spleen. Thus the effects of ACTH1-24 are probably almost entirely mediated by corticosterone. During the second week of treatment with ACTH or corticosterone the plasma corticosterone concentration was lower than during the first week. Replacing corticosterone implants at Day 7 did not cause plasma corticosterone concentration to return to that observed in the first week suggesting increased removal of the hormone from the circulation. This response resembles the stress-induced change in circulating corticosterone and may be part of the process of adaptation.

Stress of transportation for broilers.

Transporting birds for two to four hours over distances of up to 224 km (140 miles) induced hyperlipacidaemia and hypoglycaemia while the concentration of plasma cholesterol decreased and then increased significantly. These responses were the same in summer and winter. Body temperature was not affected by the experimental conditions. There was a consistent increase in plasma corticosterone which was greater in winter than in summer.

Failure to induce stress reactions following vaccination against Marek's disease or Newcastle disease.

Chickens aged one or 21 days were given single injections of a vaccine against Marek's disease or Newcastle disease respectively, and monitored over a three week period for any signs of a stressor response. No consistent evidence of such a response was found. Some data on normal ontogenetic changes in various adrenal and plasma variables are also presented.

Effects of metyrapone on plasma corticosterone concentration in Gallus domesticus.

Metyrapone (75 or 150 mg/kg body wt) was injected into fed and starving birds and their plasma corticosterone concentrations monitored. Metyrapone stimulated a hypercorticosteronaemia in fed but not in starving birds. It persisted for up to 4 hr. No significant hypocorticosteronaemia was noted subsequently. Pretreatment (2 hr) with metyrapone inhibited the response to exogenous ACTH.

Re-establishment of the stress response in Gallus domesticus after hatching.

Cold caused a hypercorticosteronaemia and hypothermia in the 2-day-old chick. Heat did not affect plasma corticosterone concentrations, despite the birds becoming hyperthermic. The 2-day-old chick has a lower resting concentration of corticosterone than the 1-day-old. The minimum effective dose of corticotrophin in stimulating a hypercorticosteronaemia was 0.5 IU/kg in the former, 1.0 IU/kg in the latter. It is concluded that stress non-responsiveness persists for about 48 hr after hatching and that it is due to a temporary inhibition of hypothalamic function.

Floor space allowances for the caged domestic fowl.

The maximal cross-sectional area, the length and the width of 48 pure bred hens weighing between 1 and 4 kg were determined using a photographic technique. It is shown that the typical (2.4 kg) bird occupies an area of 637 cm2 but that this value is much affected by the degree of feathering. The same bird is 21.3 cm wide and 41 cm long. Space allowances for caged birds are discussed in the light of these data.

Dietary ascorbic acid or procaine penicillin and the response of the immature fowl to stressors.

1. The effectiveness of dietary ascorbic acid and procaine penicillin in ameliorating the response to the stressors glucagon, corticotrophin, withdrawal of food and water and extremes of environmental temperature, both short and long-term, has been assessed. 2. No consistent changes in the responses were found, but it is suggested that the rates of inclusion of the substances may be important.

Effects of repeated injections of glucagon on the stress response of the immature fowl.

Chicks aged two weeks were injected with either glucagon (50 micrograms/kg) or solvent daily for seven days. The two groups were then divided into two subggroups and received either glucagon or saline and their lipacid and glycaemic responses determined over a 60 minute period. Neither response was modified by the earlier treatment with glucagon. Birds that had received doses of glucagon were found to have increased concentrations of corticosterone in the blood plasma and a tendency to increased concentrations of free fatty acids. The increase in plasma corticosterone induces by a novel injection of glucagon, did not occur when the eighth injection was given.