Tumor marker studies of cervical smears. Potential for automation

The distribution of three tumor markers, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA) and prekeratin (PK) was studied in exfoliated epithelial cells in cervical smears using an immunoalkaline phosphatase staining technique to demonstrate the antigens. EMA was expressed by abnormal cells in a consistent and reproducible fashion whereas the other two markers were variably expressed by both normal and abnormal cells. Our results suggest that immunocytochemical staining for EMA could be of value not only for the diagnosis of cervical intraepithelial neoplasia but also for the automated screening of cervical smears.     

Carbon balance gradient in European forests: should we doubt ‘surprising’ results? A reply to Piovesan & Adams

This paper responds to the Forum contribution by Piovesan & Adams (2000) who criticized the results obtained by the EUROFLUX network on carbon fluxes of several European forests. The major point of criticism was that the data provided by EUROFLUX are inconsistent with current scientific understanding. It is argued that understanding the terrestrial global carbon cycle requires more than simply restating what was known previously, and that Piovesan & Adams have not been able to show any major conflicts between our findings and ecosystem or atmospheric‐transport theories.     

Variations in 13C discrimination during CO2 exchange by Picea sitchensis branches in the field

We report diurnal variations in (13)C discrimination ((13)Delta) of Picea sitchensis (Bong.) Carr. branches measured in the field using a branch chamber technique. The observations were compared to predicted (13)Delta based on concurrent measurements of branch gas exchange. Observed (13)Delta values were described well by the classical model of (13)Delta including isotope effects during photorespiration, day respiration and CO(2) transfer through a series of resistances to the sites of carboxylation. A simplified linear of model (13)Delta did not capture the observed diurnal variability. At dawn and dusk, we measured very high (13)Delta values that were not predicted by either of the said models. Exploring the sensitivity of (13)Delta to possible respiratory isotope effects, we conclude that isotopic disequilibria between the gross fluxes of photosynthesis and day respiration can explain the high observed (13)Delta values during net photosynthetic gas exchange. Based on the classical model, a revised formulation incorporating an isotopically distinct substrate for day respiration was able to account well for the high observed dawn and dusk (13)Delta values.     

Equal reproductive success of phenotypes in the Larus glaucescens–occidentalis complex

Glaucous‐winged gulls Larus glaucescens and western gulls L. occidentalis hybridize extensively where their ranges overlap along the coasts of Washington and Oregon, producing a continuum of phenotypic intergrades between the two parental species. This zone often is considered an example of geographically bounded hybrid superiority, but studies of relative success among parental types and hybrids have not provided consistent support for this model. We tested the predictions of the dynamic‐equilibrium and geographically bounded hybrid superiority hypotheses by studying mate choice and reproductive success among gulls on Protection Island, Washington, the largest breeding colony of glaucous‐winged/western gulls within the hybrid zone. The dynamic‐equilibrium hypothesis posits that hybridization due to dispersal balances selection against less fit hybrids and assortative mating is adaptive. Geographically bounded hybrid superiority posits that hybrids are better fit than parental types within an ecotone between the environments to which the parental species are adapted, and a preference for hybrid mates is adaptive. Additionally, we investigated whether hatching success and nest site choice are correlated for Protection Island gulls. We assigned a hybrid index to each sample bird by examining plumage melanism and bare part coloration in the field. Sheltered nests contained larger clutches and exhibited increased hatching success, but choice of nest habitat was not associated with hybrid index. Western gull‐like pairs produced smaller third eggs; however, hybrid index was not correlated with clutch size or hatching success. Protection Island gulls did exhibit assortative mating. In short, we did not find strong support for either geographically bounded hybrid superiority or the dynamic‐equilibrium hypothesis.     

Allometric equations for integrating remote sensing imagery into forest monitoring programmes

Remote sensing is revolutionizing the way we study forests, and recent technological advances mean we are now able – for the first time – to identify and measure the crown dimensions of individual trees from airborne imagery. Yet to make full use of these data for quantifying forest carbon stocks and dynamics, a new generation of allometric tools which have tree height and crown size at their centre are needed. Here, we compile a global database of 108753 trees for which stem diameter, height and crown diameter have all been measured, including 2395 trees harvested to measure aboveground biomass. Using this database, we develop general allometric models for estimating both the diameter and aboveground biomass of trees from attributes which can be remotely sensed – specifically height and crown diameter. We show that tree height and crown diameter jointly quantify the aboveground biomass of individual trees and find that a single equation predicts stem diameter from these two variables across the world's forests. These new allometric models provide an intuitive way of integrating remote sensing imagery into large‐scale forest monitoring programmes and will be of key importance for parameterizing the next generation of dynamic vegetation models.