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.     

Occurrence of Horizontal Gene Transfer of PIB-type ATPase Genes among Bacteria Isolated from the Uranium Rich Deposit of Domiasiat in North East India

Uranium (U) tolerant aerobic heterotrophs were isolated from the subsurface soils of one of the pre-mined U-rich deposits at Domiasiat located in the north-eastern part of India. On screening of genomic DNA from 62 isolates exhibiting superior U and heavy metal tolerance, 32 isolates were found to be positive for P_IB-type ATPase genes. Phylogenetic incongruence and anomalous DNA base compositions revealed the acquisition of P_IB-type ATPase genes by six isolates through horizontal gene transfer (HGT). Three of these instances of HGT appeared to have occurred at inter-phylum level and the other three instances indicated to have taken place at intra-phylum level. This study provides an insight into one of the possible survival strategies that bacteria might employ to adapt to environments rich in uranium and heavy metals.     

Metabolism of Caffeine and Related Purine Alkaloids in Leaves of Tea (Camellia sinensis L.)

Purine alkaloid catabolism pathways in young, mature and agedleaves of tea (Camellia sinensis L.) were investigated by incubatingleaf sections with ¹⁴C-labelled theobromine, caffeine, theophyllineand xanthine. Incorporation of label into CO₂ was determinedand methanol-soluble metabolites were analysed by high-performanceliquid chromatography-radiocounting and thin layer chro-matography.The data obtained demonstrate that theobromine is the immediateprecursor of caffeine, which accumulates in tea leaves becauseits conversion to theophylline is the rate limiting step inthe purine alkaloid catabolism pathway. The main fate of [8-¹⁴C]theophyllineincubated with mature and aged leaves, and to a lesser extentyoung leaves, is conversion to 3-methylxanthine and onto xanthinewhich is degraded to ¹⁴CO₂ via the purine catabolism pathway.However, with young leaves, sizable amounts of [8-¹⁴C]-theophyllinewere salvaged for the synthesis of caffeine via a 3-methylxanthine     

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.     

Patterns of junctional communication in skin: Studies on cultured keratinocytes

Junctional communication has long been suggested to play a role in coordinating the development of multicellular tissues. A better understanding of the patterns of communication between cells in such tissues is important for the identification of areas where this process may have a role. We have investigated the patterns of communication in cultures of human epidermal keratinocytes by iontophoretic injection of Lucifer Yellow CH, using involucrin expression as a marker of cells undergoing terminal differentiation. Cells that lack involucrin (i.e., the basal, proliferating cells) transfer dye preferentially to other involucrin-negative cells, whereas involucrin-positive cells either are not coupled or transfer dye with similar frequency to involucrin-positive and involucrin-negative neighbors. This decrease in communication associated with terminal differentiation was observed in both the presence and the absence of assembled desmosomes. Our observations lead us to speculate that loss of junctional communication may influence the commitment of basal keratinocytes to terminal differentiation.     

Detecting estrus in synchronized heifers-using tailpaint and an aerosol raddle

A synchronization treatment was initiated when each of 1227 heifers (four trials) was tailpainted. The tailpaint was sprayed with an aerosol raddle at the end of the treatment period. The heifers were in herds of 20 to 279 animals. Each herd was observed for estrus at selected post treatment intervals. A heifer was considered to be (or to have been) in estrus when the raddle was rubbed off. In three of the trials, animals which had the raddle removed were inseminated at 48h following the end of the synchronization treatment. The tailpaint of an inseminated animal was scored from 0 (less than 10% of the paint remained) to 5 (more than 90% of the paint remained) and was then reraddled with a second color. The detection-insemination sequence was always repeated at 72 and 96h, and sometimes at 120h. Animals which had been previously inseminated, but then had paint scores reduced by at least 2 units were reinseminated 24h later. Over the four trials, 94.5% of the heifers were detected in estrus through the use of the tailpaint and raddle system. The remaining 67 animals included only 10 (0.8%) which had ovulated without being detected in estrus. The reinsemination rate on consecutive days was 11.3% and was highest among animals that had a tailpaint score of 4 or 5 at 48h. The proportion of animals detected in estrus at selected posttreatment intervals varied with the different synchronization treatments used within one herd, or with the same treatment used in different herds. The combination of tailpaint, raddling, tailpaint scoring and reraddling is a simple sequence which can be effectively used to detect estrus among heifers synchronized in research or commercial herds.     

Evidence of abortive recombination in ruv mutants of Escherichia coli K12

Summary Genetic recombination in Escherichia coli was investigated by measuring the effect of mutations in ruv and rec genes on F-prime transfer and mobilization of nonconjugative plasmids. Mutation of ruv was found to reduce the recovery of F-prime transconjugants in crosses with recB recC sbcA strains by about 30-fold and with recB recC sbcB sbcC strains by more than 300-fold. Conjugative plasmids lacking any significant homology with the chromosome were transferred normally to these ruv mutants. Mobilization of the plasmid cloning vectors pHSG415, pBR322, pACYC184 and pUC18 were reduced by 20- to 100-fold in crosses with ruv rec ⁺ sbc ⁺ strains, depending on the plasmid used. Recombinant plasmids carrying ruv ⁺ were transferred efficiently. With both F-prime transfer and F-prime cointegrate mobilization, the effect of ruv was suppressed by inactivating recA. It is proposed that the failure to recover transconjugants in ruv recA ⁺strains is due to abortive recombination and that the ruv genes define activities which function late in recombination to help convert recombination intermediates into viable products.