Social Learning of a Novel Foraging Skill by White-throated Magpie-jays (Calocitta formosa,Corvidae): a Field Experiment

The cooperatively breeding white-throated magpie-jay (Calocitta formosa) uses a variety of foraging tactics to find, harvest, and process food. Members of territorial groups forage together and may gain information about how to acquire food by observing each other. A field experiment was performed to determine whether a novel skill, door opening to gain access to food, was more rapidly acquired by members of groups in which a trained individual performed the skill. A higher proportion of jays in groups with behavioural ‘models’ (trained birds that opened doors in the presence of group members) acquired the door-opening skill than those groups without models. Young birds acquired the behaviour more frequently than older individuals. Aggressive behaviour at feeders may have affected the spread of the behaviour by reducing the likelihood that individuals performed the behaviour in the presence of other group members but may also have encouraged subordinate individuals to attempt door opening rather than ‘scrounge’.     

Six things Popper would like biologists not to ignore: In memoriam, Karl Raimund Popper, 1902–1994

To honour the memory of Sir Karl Popper, I put forward six elements of his philosophy which might be of particular interest to biologists and to philosophers of biology and which I think Popper would like them not to ignore, even if they disagree with him. They are: the primacy of problems; the criticizability of metaphysics (and thus the dubiousness of materialism); how downward causation might be real; how norms should matter to scientists; why dogmatism should be avoided; how genuine science is recognizable. I preface these six things with a brief discussion of Popper's early (but later recanted) mistakes concerning biology.     

Use of the true absorption coefficient as a measure of bioavailability of radiocaesium in ruminants

Limitations of existing methods to describe the bioavailability of dietary radionuclides to ruminants (the transfer coefficient and apparent absorption coefficient) have led to the alternative suggestion of using the true absorption coefficient (A _t). Various approaches to estimatingA _t for radiocaesium, involving the intravenous administration of a second isotope, are presented and discussed with reference to results from studies in which a range of radiocaesium sources were examined in sheep. Although estimates ofA _t differed between the sources, they were reasonably consistent between measurement techniques. Those methods which involved the estimation of endogenous faecal excretion of radiocaesium could be used with previously contaminated animals and did not require continuous administrations of radiocaesium isotopes, but gave unreliable results for sources of low bioavailability. Methods based on estimating the turnover rate of dietary radiocaesium through blood plasma were sufficiently sensitive to measureA _t for the range of sources studied. However, they require previously uncontaminated animals and continuous administration of both isotopes for approximately 7 days. Bioavailability is more effectively measured asA _t than as the transfer or apparent absorption coefficients sinceA _t does not incorporate factors relating to the metabolism of radiocaesium in the tissues of the animal. The results of these studies show that differences in transfer coefficients between sheep and cattle and between sheep of differing ages are not due to variation in absorption across the gut. The potential for applying these approaches to other radioactive elements is discussed.     

Effect of concentration and environmental form of tetradecenyl succinic acid on its mineralization in soil

Tetradecenyl succinic acid (TSA) is the major component of a detergent builder (C12-C14 alkenyl succinic acid), which is inherently biodegradable. ¹⁴C-TSA was dosed as a component of sewage sludge into a soil with a history of sludge amendment at final added concentrations of 1.5 and 30 mg (kg soil)^-1. In addition, it was dosed to the soil in an aqueous solution to a final added concentration of 30 mg (kg soil)^-1. Dose and form were found to have a pronouced effect on the mineralization kinetics. When dosed in a realistic form and concentration (i.e. 1.5 mg (kg soil)^-1 as a component of sludge), TSA was mineralized at its highest rate and to its greatest extent, and the mineralization half-life was 2.4 days. When dosed at 30 mg (kg soil)^-1 as a component of sludge, mineralization began immediately, and the half-life was 23 days. In contrast, when dosed at this concentration in aqueous solution, the onset of mineralization was preceded by a 13 day lag period and the mineralization half-life was 69 days. Primary biodegradation and mineralization rates of TSA were very similar. Approximately, half the radioactivity was evolved as ¹⁴CO₂, while the remaining radioactivity became non-extractable, having presumably been incorporated into biomass or natural soil organic matter (humics). This study demonstrated that TSA is effectively removed from sludge-amended soils as a result of biodegradation. Furthermore, it showed the effect that dose form and concentration have on the biodegradation kinetics and the importance of dosing a chemical not only at a relevant concentration but also in the environmental form in which it enters the soil environment.     

Flocculation of industrial and laboratory strains ofSaccharomyces cerevisiae

Summary A comparative study has been made of different laboratory and industrial wild-type strains ofSaccharomyces cerevisiae in relation to their flocculation behavior. All strains were inhibited by mannose and only one by maltose. In regard to the stability of these characters in the presence of proteases and high salt concentrations, a relevant degree of variation was found among the strains. This was to such an extent that it did not allow their inclusion in the Flol or NewFlo phenotypes. Genetic characterization of one wild-type strain revealed that the flocculation-governing gene was allelic toFLO1 found in genetic strains.This paper is dedicated to Professor Herman Jan Phaff in honor of his 50 years of active research which still continues.     

Genetic conflict and evolution of mammalian X-chromosome inactivation

The existence of parentally imprinted gene expression in the somatic tissues of mammals and plants can be explained by a theory of intragenomic genetic conflict, which is a logical extension of classical parent-offspring conflict theory. This theory unites conceptually the phenomena of autosomal imprinting and X-chromosome inactivation. We argue that recent experimental studies of X-chromosome inactivation and andro-genetic development address previously published predictions of the conflict theory, and we discuss possible explanations for the occurrence of random X-inactivation in the somatic tissues of eutherians. © 1995 Wiley-Liss, Inc.     

Mismatch Repair Genes on Chromosomes 2p and 3p Account for a Major Share of Hereditary Nonpolyposis Colorectal Cancer Families Evaluable by Linkage

Two susceptibility loci for hereditary nonpolyposis colo-rectal cancer (HNPCC) have been identified, and each contains a mismatch repair gene: MSH2 on chromosome 2p and MLH1 on chromosome 3p. We studied the involvement of these loci in 13 large HNPCC kindreds originating from three different continents. Six families showed close linkage to the 2p locus, and a heritable mutation of the MSH2 gene was subsequently found in four. The 2p-linked kindreds included a family characterized by the lack of extracolonic manifestations (Lynch I syndrome), as well as two families with cutaneous manifestations typical of the Muir-Torre syndrome. Four families showed evidence for linkage to the 3p locus, and a heritable mutation of the MLH1 gene was later detected in three. One 3p-linked kindred was of Amerindian origin. Of the remaining three families studied for linkage, one showed lod scores compatible with exclusion of both MSH2 and MLH1, while lod scores obtained in the other two families suggested exclusion of one HNPCC locus (MSH2 or MLH1) but were uninformative for markers flanking the other locus. Our results suggest that mismatch repair genes on 2p and 3p account for a major share of HNPCC in kindreds that can be evaluated by linkage analysis.     

Gravity-regulated formation of the peg in developing cucumber seedlings

It has been proposed that peg formation in the vascular transition region (TR zone) between the hypocotyl and the root in Cucurbitaceae seedlings is a gravimorphogenetic phenomenon. Initiation of the peg became visible 36 h after imbibition when cucumber (Cucumis sativus L. cv. Burpee Hybrid II) seeds were germinated in a horizontal position at 24°C in the dark. Simultaneously, sedimented amyloplasts (putative statoliths) were apparent in the sheath cells surrounding the vascular strands, and in the cortical cells immediately adjacent to them, in the TR zone. In contrast, the other cortical cells, some of which were destined to develop into the peg, contained amyloplasts which were not sedimented. These results suggest that the graviperception mechanism for peg formation may be like that of statoliths in shoot gravitropism. By 48 h following imbibition, the cells of the TR zone still had sedimented amyloplasts but had lost their sensitivity to gravity, possibly because of their maturation.     

Cloning and Expression of a 5-Hydroxytryptamine7 Receptor Positively Coupled to Adenylyl Cyclase

Abstract: In a number of different cell types, phosphorylation of a 63-kDa protein has been shown to increase rapidly in response to stimuli that lead to an increase in intracellular calcium. Here, a stimulus-sensitive protein at this molecular weight is identified in PC12 cells and rat cortical synaptosomes as phosphoglucomutase. In addition, the added phosphate is shown to be in an oligosaccharide terminating in phosphodiester-linked glucose. In synaptosomes, incorporated radioactivity, following incubation with [¹⁴C]glucose or the [β-³⁵S]phosphorothioate analogue of UDP-glucose, was found to increase within 5 s of stimulation and return to baseline within 25 s. Despite the many pathways utilizing glucose, this was the only detectable protein glycosylation observed in synaptosomes. These results indicate that cytoplasmic glycosylation is reversible and rapidly regulated, and suggest that phosphoglucomutase undergoes an alteration in function and/or topography in response to increases in intracellular calcium.