Does maternal condition or predation risk influence small mammal population dynamics?

There is strong debate over whether the intrinsic traits of individuals or the extrinsic environment exert the greater influence on small mammal population dynamics. We test the roles of maternal effects (an intrinsic factor) and predation risk (an extrinsic factor) in the population dynamics of wild strain house mice using a 2-factor enclosure experiment. Pre-release supplemental feeding with a high-fat diet created female treatment founders that were 6–10% heavier than controls, a condition that we predicted would be passed on as a maternal effect. Predation risk was enhanced using regular application of predator (red fox Vulpes vulpes ) scats. Founder populations of six females and six males released into eight, 15×15 m enclosures showed near exponential population growth over 17 weeks (maximum 3 generations). But there were no responses to either treatment in terms of survival, inherited body weights, fecundity or population size. We suggest that elevated maternal condition may have only minor and transient intergenerational effects with little long-term consequence. We also suggest that the general significance of predator scats as a cue to predation risk to alter prey behaviour may have been overestimated. Hence our results question the role of either factor in causing long-term responses that influence condition to affect population processes.     

Ecosystem function and species loss – a microcosm study

There are too many kinds of organisms to be able to study and manage each, yet the loss of a single species can sometimes unravel an ecosystem. Such `fusewire species'– critical in the same sense that an electrical fuse can cut out a whole circuit – would be a rewarding focus for research and management effort. However, this approach can only be effective if these `fusewires' represent but a small proportion of the number of species in the system.  

Aim

To demonstrate methods for measuring what proportion of the species in a system are critical to ecosystem function.  

Methods

The prevalence of fusewire species was measured in manipulative experiments on an aquatic microcosm.  

Results

No single genus deletion caused changes in key characteristics of the system.  

Main conclusions

Comparison of these results with other published studies shows that the proportion of critical fusewire species varies amongst different ecosystems. The oxidation pond microcosms were shown to contain no single species indispensable to system function. They appear to be ill-suited to a management strategy which focuses on priority eukaryote species. However, a single study provides no evidence that this result is general or even typical of other kinds of ecosystems; it is presented here as an empirical model. Other methods of investigation are available; they are less experimentally rigorous but more practical. These could provide important guidance in planning an approach to management in a particular ecosystem.     

The asparagine-linked sugar chains of human follicle-stimulating hormone

The asparagine-linked sugar chains of human follicle-stimulating hormone (hFSH) were liberated as radioactive oligosaccharides from the polypeptide moiety by hydrazinolysis followed by N-acetylation and NaB3H4 reduction. Ninety-five percent of the oligosaccharides were acidic and all were converted to a mixture of neutral oligosaccharides on sialidase treatment. The mixture of neutral oligosaccharides was subjected to sequential immobilized lectin column chromatography on E-PHA-agarose, AAL-Sepharose, and Con A-Sepharose, and six fractions were obtained. The results of sequential exoglycosidase digestion of each oligosaccharide and methylation analysis led us to propose that the asparagine-linked sugar chains of hFSH are a mixture of complex-type bi-, tri-, and tetraantennary sialylated sugar chains with and without a fucose residue linked at the C-6 position of the proximal N-acetylglucosamine. Some of these sugar chains contain bisecting N-acetylglucosamine residue.     

Monoclonal antibodies to the two most basic papaya proteinases

The proteinases fromCarica papaya include papain, isoenzymes of chymopapain and two proteinases A and B distinguished by their unusually high pI. The identity of one of the most basic proteinases has been questioned. The present report describes the preparation and characterisation of two monoclonal antibodies that react specifically with papaya proteinases A and B respectively and a third that identifies a common structural feature found in papain and proteinase A.     

Use of 6-diazo-5-oxo-l-norleucine to study interaction between myocardial glycoconjugate secretion and endothelial activation in the early embryonic chick heart

The glutamine analog, 6-diazo-5-oxo-l-norleucine (DON), a glycoconjugate inhibitor, was used to probe the relationships between myocardial secretion of extracellular matrix and endothelial differentiation and formation of cushion mesenchyme (primordia of AV values). When DON was given to stage 12 chick embryos maintained in shell-less culture, the myocardial secretion gradient of glucose- and sulfate-labeled matrix was blocked. Concomitantly, the endothelium failed to complete activation but continued to divide and incorporate thymidine. By varying DON concentration, two distinct phases of endothelial differentiation were identified: the first (labile to 0.5 μg) involved hypertrophy, the second (labile to 0.25 μg) acquisition of migratory appendages with resultant mesenchyme formation. Glucosamine + DON (but not inosine, glucose, or glutamine) restored the matrical secretion gradient and to varying degrees both phases of endothelial activation. Endothelia totally suppressed from forming mesenchyme in situ acquired this capacity when explanted into three-dimensional collagen gel culture. The capacity was enhanced by glucosamine given in situ as an inhibitory override, dependent upon serum concentration, inhibited by heat-inactivated serum or by adding DON to the medium, but unaffected by hyaluronate. These results were compared to those obtained by co-culturing endothelium and myocardium and discussed in terms of the hypothesis that cushion mesenchyme formation results from an epithelial interaction mediated by glycoconjugates.     

Ultrastructural identification of corticotropes of the fetal rat

Corticotropes of rat fetuses aged 16, 18 and 21 days were localized by the indirect antibody-enzyme method on semithin sections of the pituitary. The development of the ultrastructure of these cells was observed on consecutive ultrathin sections. In comparison with previous data our present results show that identification of a fetal cell type cannot be based entirely on morphological criteria. The structural peculiarities of corticotropes obtained from studies in vivo are compared with those observed in cells maintained in vitro.     

Molecular and functional analysis of the ruv region of Escherichia coli K-12 reveals three genes involved in DNA repair and recombination

Summary Recombinant plasmids carrying ruvA, ruvB, or both were constructed and used to investigate the genetic defects in a collection of UV-sensitive ruv mutants. The results revealed that efficient survival of UV-irradiated cells depends on both ruvA and ruvB, and on a third gene, ruvC, located upstream of the ruvAB operon. Southern blotting analysis was used to locate insertions in ruv and to examine putative deletion mutants. Two Tn10 insertions were located to the region encoding ruvA. Since these insertions caused a deficiency in the activities of both ruvA and ruvB, we concluded that they must exert a polar effect on ruvB. Two putative ruv deletion mutants were shown to be the result of deletion-inversion events mediated during imprecise excision of Tn10. The relevant inversion breakpoints in these mutants were located to ruvA and ruvC.