Living with observational data in biological anthropology

The establishment of cause and effect relationships is a fundamental objective of scientific research. Many lines of evidence can be used to make cause–effect inferences. When statistical data are involved, alternative explanations for the statistical relationship need to be ruled out. These include chance (apparent patterns due to random factors), confounding effects (a relationship between two variables because they are each associated with an unmeasured third variable), and sampling bias (effects due to preexisting properties of compared groups). The gold standard for managing these issues is a controlled randomized experiment. In disciplines such as biological anthropology, where controlled experiments are not possible for many research questions, causal inferences are made from observational data. Methods that statisticians recommend for this difficult objective have not been widely adopted in the biological anthropology literature. Issues involved in using statistics to make valid causal inferences from observational data are discussed.     

Full field spatially-variant image-based resolution modelling reconstruction for the HRRT

Accurate characterisation of the scanner's point spread function across the entire field of view (FOV) is crucial in order to account for spatially dependent factors that degrade the resolution of the reconstructed images. The HRRT users' community resolution modelling reconstruction software includes a shift-invariant resolution kernel, which leads to transaxially non-uniform resolution in the reconstructed images. Unlike previous work to date in this field, this work is the first to model the spatially variant resolution across the entire FOV of the HRRT, which is the highest resolution human brain PET scanner in the world. In this paper we developed a spatially variant image-based resolution modelling reconstruction dedicated to the HRRT, using an experimentally measured shift-variant resolution kernel. Previously, the system response was measured and characterised in detail across the entire FOV of the HRRT, using a printed point source array. The newly developed resolution modelling reconstruction was applied on measured phantom, as well as clinical data and was compared against the HRRT users' community resolution modelling reconstruction, which is currently in use. Results demonstrated improvements both in contrast and resolution recovery, particularly for regions close to the edges of the FOV, with almost uniform resolution recovery across the entire transverse FOV. In addition, because the newly measured resolution kernel is slightly broader with wider tails, compared to the deliberately conservative kernel employed in the HRRT users' community software, the reconstructed images appear to have not only improved contrast recovery (up to 20% for small regions), but also better noise characteristics.     

The Value of Artificial Stimuli in Behavioral Research: Making the Case for Egg Rejection Studies in Avian Brood Parasitism

Experimentation is at the heart of classical and modern behavioral ecology research. The manipulation of natural cues allows us to establish causation between aspects of the environment, both internal and external to organisms, and their effects on animals' behaviors. In recognition systems research, including the quest to understand the coevolution of sensory cues and decision rules underlying the rejection of foreign eggs by hosts of avian brood parasites, artificial stimuli have been used extensively, but not without controversy. In response to repeated criticism about the value of artificial stimuli, we describe four potential benefits of using them in egg recognition research, two each at the proximate and ultimate levels of analysis: (1) the standardization of stimuli for developmental studies and (2) the disassociation of correlated traits of egg phenotypes used for sensory discrimination, as well as (3) the estimation of the strength of selection on parasitic egg mimicry and (4) the establishment of the evolved limits of sensory and cognitive plasticity. We also highlight constraints of the artificial stimulus approach and provide a specific test of whether responses to artificial cues can accurately predict responses to natural cues. Artificial stimuli have a general value in ethological research beyond research in brood parasitism and may be especially critical in field studies involving the manipulation of a single parameter, where other, confounding variables are difficult or impossible to control experimentally or statistically.     

A simple device to measure root growth rates

The construction and use of a simple auxanometer is described. With this instrument students can readily and accurately measure root growth rates of intact seedlings. Typical time course data are presented for the effect of ethylene and indole acetic acid on pea root growth.     

Social Biology at Whitelands College

Eothen Film Loops: Digestion, Absorption and Distribution The set consists of 6 loops: ref 815/C1-6 Price: Standard 8 mm (silent) £7–75 each. Super 8 mm (silent) £6–50 each

Film Loops for the Nuffield Advanced Biological Science Project Available from: Penguin Education Ltd, Harmondsworth, West Drayton, Middx UB7 8EP     

A blood sampling technique for prehatched chicks

ABSTRACT Collecting blood from neonatal or prehatched chicks is sometimes necessary, requiring specialized blood collection techniques and skills. However, such sampling can be difficult and could potentially have adverse effects. I developed a method for collecting blood from chicks still in an egg. The technique involves enlarging the pipping hole, removing the chick's head to take blood from a jugular vein, and returning the chick into its original position in the egg to complete hatching back in the nest. I used this technique on Crested Tern (Thalasseus bergii) chicks (N= 13), with no apparent adverse effects to growth or short‐term survival. The amount of blood extracted (0.1–0.15 ml) was sufficient for a blood smear, hematocrit, and total white blood cell count. This method should be useful for eggs as small as 40 mm in length; eggs smaller than this would likely not be good candidates for this technique because eggshells may be too thin to safely handle. This technique may be useful for investigators studying the immunological and endocrinological transition between embryos and hatchlings.     

A Probasin‐MerCreMer BAC allows inducible recombination in the mouse prostate

Tissue‐specific transgene expression in the prostate epithelium has previously been achieved using short prostate‐specific promoters, rendering transgenic mouse lines susceptible to integration site‐dependent effects. Here we demonstrate the applicability of bacterial artificial chromosome (BAC) technology to transgene expression in the prostate epithelium. We present mouse lines expressing an inducible Cre protein (MerCreMer) under the control of regulatory elements of the probasin gene on a BAC. These mouse lines show high organ specificity, high transgene expression in anterior, dorsal and lateral prostate lobes, no background Cre recombination using a reporter strain and adjustable amounts of Cre‐induced recombination upon tamoxifen induction. Together with two recently reported transgenic lines expressing the Cre‐ERT2 protein from small prostate‐specific promoters, these mouse lines will be useful in research focused on prostate‐specific disorders such as benign hyperplasia or cancer. genesis 47:757–764, 2009. © 2009 Wiley‐Liss, Inc.     

Effect of bialaphos and phosphinothricin on plant regeneration from long- and short-term callus cultures of Gladiolus

Summary Callus was initiated from in vitro-grown plants of Gladiolus cultivars ‘Jenny Lee’ and ‘Florida Flame.’ The age of callus used for regeneration of plants was either 9 mo. old or 8 yr old from ‘Jenny Lee,’ and 4 mo. old from ‘Florida Flame.’ Regeneration medium consisted of Murashige and Skoog’s basal salts medium supplemented with 2.0 mg/l (9.3 μM) kinetin. This medium was supplemented with various concentrations of either bialaphos (Meiji Seika, Tokyo, Japan) or phosphinothricin (Hoechst-Roussell, Frankfurt, Germany). Bialaphos was more effective than phosphinothricin at stimulating plant regeneration. Plants regenerated from 8-yr-old callus of ‘Jenny Lee’ only when the regeneration medium was supplemented with 0.10 mg/l bialaphos. A bialaphos concentration of 0.01 mg/l stimulated regeneration from 9-mo.-old callus of cultivar ‘Jenny Lee’ and 4-mo.-old callus of ‘Florida Flame.’