Decreased Accumulation of Cadmium in Drosophila Selected for Resistance Suggests a Mechanism Independent of Metallothionein

Heavy metals, including cadmium, are common contaminants in environments subject to human activity. Responses to exposure in the fruit fly, Drosophila melanogaster, are dosage-dependent and resistance is selectable. While metallothionein-mediated sequestration has been extensively studied as a mechanism of cadmium resistance, a link between selection for resistance and an increased accumulation of cadmium has yet to be demonstrated. To address this need, we have selected wild-type flies for cadmium resistance for 20 generations and tested metal content using mass spectrometry. Resistant flies were observed to contain lower levels of cadmium, arguing for a mechanism of cadmium resistance that is not mediated by increased sequestration. This, coupled with genetic evidence suggesting the involvement of factors located on the X chromosome, suggests a gene other than metallothionein may be involved in resistance in this line.     

BACUP--the first two years: evaluation of a national cancer information service.

The cancer information service of the British Association of Cancer United Patients (BACUP) was launched in October 1985 as a national service to patients and their relatives, the public, and health professionals. Information is provided by telephone and letter by seven nurses trained in oncology. In the first two years over 30,000 inquiries were received: 23,527 (80%) were from women; 9445 (32%) were from cancer patients 11,574 (39%) from relatives of patients, and 2869 (10%) from health professionals. Inquiries came from all over the United Kingdom and from all sections of society but users were predominantly middle class, aged between 30 and 49, and living in south east England. Information about specific cancer sites, treatment, and how to cope was most commonly sought. Nearly a third of all inquiries were related to breast cancer. Though the service is used more by particular groups focusing on particular diseases, clearly there is a need for a cancer information service in the UK.     

A model of vascular compression in solid tumours

Often when a vascularized solid tumour reaches a diameter of 1–3 cm, central vascular compression occurs and the blood flow is confined to the peripheral outer layer. Here a model is presented which develops the concept that this vascular compression is due to the combined effect of the proliferation of cells inside the tumour and the pressure exerted on the tumour by the surrounding tissue. It is hypothesized that this occlusion eventually causes central necrosis.     

Stomatal Density and Index of Fossil Plants Track Atmospheric Carbon Dioxide in the Palaeozoic

It has been demonstrated that the leaves of a range of foresttree species have responded to the rising concentration of atmosphericCO₂ over the last 200 years by a decrease in both stomatal densityand stomatal index. This response has also been demonstratedexperimentally by growing plants under elevated CO₂ concentrations.Investigation of Quaternary fossil leaves has shown a correspondingstomatal response to changing CO₂ concentrations through a glacial-interglacialcycle, as revealed by ice core data. Tertiary leaves show asimilar pattern of stomatal density change, using palynologicalevidence of palaeo-temperature as a proxy measure of CO₂ concentration.The present work extends this approach into the Palaeozoic fossilplant record. The stomatal density and index of Early Devonian,Carboniferous and Early Permian plants has been investigated,to test for any relationship that they may show with the changesin atmospheric CO₂ concentration, derived from physical evidence,over that period. Observed changes in the stomatal data givesupport to the suggestion from physical evidence, that atmosphericCO₂ concentrations fell from an Early Devonian high of 10-12times its present value, to one comparable to that of the presentday by the end of the Carboniferous. These results suggest thatstomatal density of fossil leaves has potential value for assessingchanges in atmospheric CO₂ concentration through geologicaltime.Copyright 1995, 1999 Academic Press Aglaophyton major, Sawdonia ornata, Swillingtonia denticulata, Lebachia frondosa, Juncus effusus, Psilotum nudum, Araucaria heterophylla, stomatal density, stomatal index, Palaeozoic CO₂     

The influence of climate on the spatial patterning of Neotropical plant families

Aim Climate is recognized for the significant role it plays in the global distribution of plant species diversity. We test the extent to which two aspects of climate, namely temperature and precipitation, explain the spatial distribution of high taxonomic groupings (plant families) at a regional spatial resolution (the Neotropics). Our goal is to provide a quantitative and comparative framework for identifying the local effects of climate on the familial composition of tropical forests by identifying the influence of climate on the number of individuals and the number of species within a given family. Location One hundred and forty‐four 0.1‐ha forest transect sites from the Neotropics (19.8°N–27.0°S and 40.1°W–105.1°W). Data were originally collected by A.H. Gentry. Methods Spatial variability in the abundance (density) and species richness of 159 tropical plant families across a range of predominately lowland Neotropical landscapes were attributed to eight temperature and precipitation measures using the eigen analysis method of two‐field joint single‐value decomposition. Results Climate significantly affects the within‐clade diversity of several ecologically important Neotropical plant families. Intrafamily abundance and richness covary with temperature in some families (e.g. Fabaceae) and with precipitation in others (e.g. Bignoniaceae, Arecaceae), with differing climatic preferences observed even among co‐occurring families. In addition, the family‐level composition of Neotropical forests, in both abundance and richness, appears to be influenced more by temperature than by precipitation. Among lowland families, only Asteraceae increased in species richness with decreasing temperature, although several families, including Melastomataceae and Rubiaceae, are more abundant at lower temperatures. Main conclusions Although plant diversity is known to vary as a function of climate at the species level, we document clear climatic preferences even at the rank of family. Temperature plays a stronger role in governing the familial composition of tropical forests, particularly in the richness of families, than might be expected given its narrow annual and diurnal range in the tropics. Although other environmental or geographic variables that covary with temperature may be more causally linked to diversity differences than temperature itself, the results nonetheless identify the taxonomic components of tropical forest composition that may be most affected by future climatic changes.     

Selective detachment of mitotic cells by hypotonic salt solution

Summary A method has been developed to obtain synchronous populations from a human cell line which previously resisted the use of the selective harvest technique. A concentration of Colcemid was determined which reversibly enriched the mitotic population but avoided delays in cell cycle progression. Mitotic cells were then detached from monolayer cultures by brief treatment with hypotonic salt solutions. The resulting populations of line A244 were shown to be viable and syntchronous by following attachment efficiency and cycle time and by monitoring mitotic index and deoxyribonucleic acid synthesis. Hypotonic solutions offer no advantage in the selection of mitotic L-929 cells, a line commonly synchronized by selective harves. However, their use with both CV-1 and A244 cells provided large populations highly synchronized with respect to mitosis. This technique might be applied successfully to cell types which do not demonstrate a selective advantage at division.