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.     

Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains

Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains. The enzyme in strain BK5 is shown to be both functionally and structurally related to the nitrate reductase of Paracoccus denitrificans and Escherichia coli.Abbreviation TMAO trimethylamine-N-oxide     

Genetic analysis and molecular cloning of the Escherichia coli ruv gene

Summary The genetic organisation of the ruv gene, a component of the SOS system for DNA repair and recombination in Escherichia coli, was investigated. New point mutations as well as insertions and deletions were generated using transposon Tn10 inserted in eda as a linked marker for site specific mutagenesis, or directly as a mutagen. The mutations were ordered with respect to one another and previously isolated ruv alleles by means of transductional crosses. The direction of chromosome mobilization from ruv:: Mud(Ap^R lac)strains carrying F42lac ⁺ established that ruv is transcribed in a counterclockwise direction. Recombinant phages able to restore UV resistance to ruv mutants were identified, and the ruv ⁺ region was subcloned into a low copy number plasmid. The ruv ⁺ plasmid was able to correct the extreme radiation sensitivity and recombination deficiency of ruv recBC sbcB strains.     

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.     

Change in cough reflex after treatment with enalapril and ramipril.

OBJECTIVE--To find out whether enalapril or ramipril causes the sensitivity of the cough reflex to change or symptomatic cough to develop in patients with hypertension. DESIGN--Prospective, placebo controlled, double blind, randomised crossover study. SETTING--Academic units of clinical pharmacology and medicine. PATIENTS--20 Patients (nine men and 11 women) who needed to take angiotensin converting enzyme inhibitors to control hypertension. INTERVENTIONS--All patients received enalapril 10 mg daily, ramipril 10 mg daily, or placebo daily for one week in random order, with a washout period of at least one week between treatments. For assessment of sensitivity of the cough reflex the patients inhaled various concentrations of capsaicin solution in random order. MAIN OUTCOME MEASURES--Measurement of the doses of capsaicin required to cause two or more and five or more coughs or the development of a symptomatic cough. RESULTS--Blood pressure, symptoms of cough, and the sensitivity of the cough reflex to inhaled capsaicin were recorded at the start of the study and before and at the end of each treatment period. Plasma urea and creatinine concentrations and angiotensin converting enzyme activity were measured at the start of the study and the end of each treatment period. Data were analysed by two way analysis of variance. Mean blood pressure was 159/97 mm Hg at the start of the study and 152/92, 143/88, and 147/86 mm Hg after treatment with placebo, enalapril, and ramipril respectively. Mean (SE) plasma angiotensin converting enzyme activity was 2.2 (0.2) mmol/l/h after treatment with placebo and fell significantly to 1.3 (0.1) mmol/l/h and to 0.4 (0.1) mmol/l/h after treatment with enalapril and ramipril respectively. No patient complained of cough while taking placebo but three women complained of cough when taking both enalapril and ramipril. The mean (95% confidence interval) lowest dose of capsaicin causing two or more coughs was 2.4 (1.5 to 4.0), 1.8 (1.12 to 2.82), and 2.2 (1.7 to 3.0) nmol after treatment with placebo, enalapril, and ramipril respectively; none of these changes were significant. The lowest dose of capsaicin causing five or more coughs was 18.9 (13.9 to 25.8), 14.4 (8.4 to 24.5), and 15.3 (10.8 to 21.2) nmol respectively; none of these changes were significant. The three patients who complained of cough had normal sensitivity to capsaicin after treatment with placebo but had a considerably increased sensitivity after treatment with enalapril and ramipril. CONCLUSIONS--Both enalapril and ramipril increase the sensitivity of the cough reflex appreciably in patients who complain of cough during treatment, but they do not change the se