Personal view. Is it reality or an illusion that liquid‐based cytology is better than conventional cervical smears?

Liquid-based cytology (LBC) has been heralded as the way forward for cervical screening, and as the answer to many of its problems. It is already used as a sole method of cell preparation in many private clinics in the UK. It is being used for colposcopy smears in many NHS clinics and is now being piloted for primary screening in three screening centres in England, as well as one in Scotland and one in Wales. LBC has been welcomed as a new technology because it deals with the problem of specimen adequacy at source, removing responsibility for slide preparation and fixation from the clinician or nurse. It provides uniformly well-fixed preparations that are free of inflammatory exudate and blood, and seem easier to screen than conventional smears. There are many articles in the world literature suggesting that LBC is more accurate than conventional screening, and it is thought likely to reduce the number of false negative tests. The main reasons for piloting LBC in the NHS Cervical Screening Programme (NHSCSP) lie in its potential for reducing screening times and for reducing the numbers of repeats for inadequate tests. LBC is expensive in terms of equipment, capital costs, maintenance, consumables, training, technical preparation time, transportation and disposal of liquid media. Its costs could be justified if they were offset by the money saved from reduced screening time and repeat tests, but only if its accuracy in terms of sensitivity and specificity were proven to be equal to or better than conventional cytology. Although that is generally held to be true by the public and medical profession alike, there is very little hard evidence to support it.     

A comparative analysis of population structuring and genetic diversity in sympatric lineages of freshwater shrimp (Atyidae: Paratya): concerted or independent responses to hydrographic factors?

1. We determined whether two sympatric mitochondrial DNA (mtDNA) lineages of freshwater shrimp (Decapoda: Atyidae: Paratya australiensis) represent biological species and if they had concerted or independent population responses to hydrographic factors in small streams (the Granite Creeks) in southeastern Australia. 2. Allozyme data indicated the presence of two gene pools at sites where the P. australiensis lineages were co‐occurring and the gene pools were statistically assigned with high probability to each respective lineage. This indicated that these mtDNA lineages in P. australiensis were reproductively isolated and thus biological species. 3. Populations of both lineages were genetically homogeneous among lowland sites within streams, but were isolated by steep stream gradients among upland sites and for lowland–upland site comparisons. However, the magnitude of differentiation was markedly different between the two lineages. Allozyme diversity also differed between the two lineages, suggesting that they have different effective population sizes. Thus, differences in the magnitude of genetic divergence among populations were probably because of different life‐history characteristics, including dispersal ability and population size. 4. Genetic population structure was mostly temporally stable, despite the extreme effects of drought during the first year and substantial stream‐flow during the second. However, stable isotope analyses revealed greater local movement in both lineages during the second year, as greater hydrological connectivity provided more opportunities for dispersal. Thus, although lowland populations within streams were genetically homogeneous, stable isotope data indicated that connections may be sporadic and result from accumulated small‐scale movements among refugial pools. 5. Both lineages were therefore found to have similar small‐scale population responses to the unstable habitats of the Granite Creeks. Results highlight the importance of refugia for the capacity of biota to recover from drought and the need for multiple restored patches to reinstate natural population processes (e.g. resilience, recolonization) in degraded systems.     

MODELING CONSUMER INTENTION TO PURCHASE FRESH PRODUCE

The effect of some fresh‐cut carrot label attributes on consumer purchase intention was evaluated using conjoint analysis. The following three attributes were chosen and manipulated: price (high and low), packaging type (polyethylene bags and expanded polystyrene trays) and production process (organic with certification stamp, organic without certification stamp and no information). A complete factorial design was used, and 12 hypothetical packages of fresh‐cut carrot were developed and evaluated by 96 consumers based on their purchase intention. The consumers were divided into four groups with different opinions. Low price and organic with certification label were the favorite choices of the groups. Only one group preferred expanded polystyrene trays. No interactions were exhibited among the attributes in all groups.     

Patterns of pupal mortality in field populations of Hydropsyche and Cheumatopsyche (Trichoptera: Hydropsychidae)

SUMMARY. 1. Up to 40% of hydropsychid pupal cases (from three stations on the Credit and Humber Rivers, Ontario, Canada) contained insects already dead when collected; chironomid infestation accounted for up to 82% of total mortality within a taxon from any one station. The remaining mortality appeared to be due to siltation.
2. For all taxa ( Cheumatopsyche Wallengren and four species of Hydropsyche Pictet), and at all stations, prepupae suffered significantly more chironomid-related mortality than did fully-developed pupae.
3. Chironomid infestation generally affected all species of Hydropsyche equally; at some stations, Cheumatopsyche pupae appeared to suffer less chironomid-related mortality than did co-existing Hydropsyche species.
4. Chironomid infestation affected a greater proportion of pupae at the station where the density of pupal cases (per sampling quadrat) was greatest.
5. Vertical distribution of the pupation site had no apparent influence on mortality attributed to either siltation or chironomid infestation.
6. Chironomid infestation varied seasonally; it was greatest in May and July-August at an upstream station, and peaked in June at the downstream stations.
7. Mortality attributed to siltation was relatively constant for all stages and taxa, at all stations, throughout the sampling programme.     

Competition between grass and clover in spring as affected by nitrogen fertiliser

Detailed measurements of irrigated ryegrass/white clover swards growing without interruption, with or without nitrogen fertiliser in spring, showed that the relative growth rate of clover was as great as that of grass, in the + N sward, and considerably greater than grass, in the – N sward. Clover leaves were not overtopped by grass leaves. Indeed, in both swards, clover had a greater proportion of its leaf lamina area in the upper, well lit, layers of the canopy than grass did. Consequently, clover had a greater mean rate of leaf photosynthesis in situ in the sward than grass. Clover's advantage in photosynthetic rate per leaf area was offset to some extent by its smaller ratio of leaf area to total above-ground dry weight than grass. The consequences of these results for our understanding of competition between grass and clover in mixed swards are discussed.     

Rapid northwards expansion of a forest insect pest attributed to spring phenology matching with sub‐Arctic birch

Species range displacements owing to shifts in temporal associations between trophic levels are expected consequences of climate warming. Climate‐induced range expansions have been shown for two irruptive forest defoliators, the geometrids Operophtera brumata and Epirrita autumnata, causing more extensive forest damage in sub‐Arctic Fennoscandia. Here, we document a rapid northwards expansion of a novel irruptive geometrid, Agriopis aurantiaria, into the same region, with the aim of providing insights into mechanisms underlying the recent geometrid range expansions and subsequent forest damage. Based on regional scale data on occurrences and a quantitative monitoring of population densities along the invasion front, we show that, since the first records of larval specimens in the region in 1997–1998, the species has spread northwards to approximately 70°N, and caused severe defoliation locally during 2004–2006. Through targeted studies of larval phenology of A. aurantiaria and O. brumata, as well as spring phenology of birch, along meso‐scale climatic gradients, we show that A. aurantiaria displays a similar dynamics and development as O. brumata, albeit with a consistent phenological lag of 0.75–1 instar. Experiments of the temperature requirements for egg hatching and for budburst in birch showed that this phenological lag is caused by delayed egg hatching in A. aurantiaria relative to O. brumata. A. aurantiaria had a higher development threshold (LDT_A.a.=4.71 °C, LDT_O.b.=1.41 °C), and hatched later and in less synchrony with budburst than O. brumata at the lower end of the studied temperature range. We can conclude that recent warmer springs have provided phenological match between A. aurantiaria and sub‐Arctic birch which may intensify the cumulative impact of geometrid outbreaks on this forest ecosystem. Higher spring temperatures will increase spring phenological synchrony between A. aurantiaria and its host, which suggests that a further expansion of the outbreak range of A. aurantiaria can be expected.     

The germination and the forces required to penetrate seed layers of different seedlots of three cultivars of crisp lettuce

Using 24 commercial seedlots of the lettuce cvs Ithaca, Pennlake and Saladin, the percentage germination at a range of temperatures from 20 to 35°C, and the forces required to penetrate the pericarp, the endosperm and the embryo were measured. Percentage germination declined with increasing temperature in all seedlots but there were particularly large differences between seedlots of the same cultivar at 30.0 and 32.5°C. The force required to penetrate the pericarp was on average more than twice that required to penetrate the endosperm. It is concluded that in commercial cultivars of crisp lettuce the strength of the pericarp plays a much greater role than that of the endosperm in determining germination. In all three cultivars there were significant positive correlations between seed weight and the force required to penetrate the whole seed. However only in cv. Pennlake were there significant correlations between germination at high temperature and seed penetration forces.     

The Effect of Age on the Rate of Apparent Photosynthesis in Leaves of Tall Fescue (Festuca arundinaceaSchreb.)

n apparatus is described in which the rate of apparent photosynthesisof single attached or detached grass leaves was determined bymeasuring with an infra-red gas analyser the uptake of carbondioxide from a stream of air passed over the leaves. In one experiment the apparatus was used to determine the apparentphotosynthesis at one time of the three youngest leaves removedfrom a tiller of tall fescue plants grown in the field. Resultsshowed that each older leaf had a lower rate of apparent photosynthesisthan its successor. To determine the real effect of age of theleaf without any possible interaction with position of the leafor an after-effect of environment, measurements of apparentphotosynthesis were made in two further experiments on leavesattached to the main stem on plants grown in controlled environments.Results were obtained from samples of the fifth leaf of increasingage from full expansion. These showed a progressive declinein apparent photosynthesis with increasing age: in one experimentthis was preceded by a small initial rise after complete leafexpansion. There were no marked changes in the weight of theleaf as it aged and, in consequence, the form of the resultswere similar when expressed on either a leaf area or dry weightbasis.     

Trial Implantation of Heart Rate Data Loggers in Pinnipeds

ABSTRACT Pinnipeds are major consumers in marine ecosystems, and understanding their energy budgets is essential to determining their role in food webs, particularly where there is competition with fisheries. Food consumption and energy expenditure have been evaluated in pinnipeds using different methods, but the use of heart rate to estimate energy expenditure is potentially a very powerful tool suited to the life history of these animals. We tested a procedure for the subcutaneous implantation of heart rate data loggers to determine whether heart rate could be recorded for ≥1 year in free-ranging pinnipeds, as it has been in birds. We implanted 3 captive California sea lions (Zalophus californianus) and 3 captive northern elephant seals (Mirounga angustirostris) with heart rate data loggers and monitored their recovery and behavior in a controlled environment. In both species, the implantation site allowed for excellent detection of the electrocardiogram, and we observed heart rate signatures characteristic of behaviors such as resting and diving. Although all 3 sea lions recovered well from the implantation surgery, all 3 elephant seals showed a substantial inflammatory response for unknown reasons, and we removed the implanted data loggers. Subcutaneous implantation of data loggers is a powerful technique to study physiology, energetics, and behavior in California sea lions, but more work is required to realize the potential of this technique in northern elephant seals.     

The Effect of Shading on the Photosynthetic Rate and Longevity of Grass Leaves

The rate at which the net photosynthesis of grass leaves grownin bright light (119 W m^–2) decreased as they aged wasincreased by severe shading (to 21 W m^–2 or less). However,less severe shading (light intensities of 36 W m^–2 ormore) had no effect. The decrease in photosynthesis was unaffectedby whether the whole plant was shaded or only the leaf whosephotosynthesis was measured. In both shaded and unshaded leaves, photosynthesis measuredin bright light fell faster as the leaf aged than did photosynthesisin dim light. Both mesophyll and stomatal diffusion resistancesrose as the leaf aged but the former rose faster. The chlorophyllcontent fell only towards the end of the life of the leaves.