Radiation biology of mosquitoes

There is currently renewed interest in assessing the feasibility of the sterile insect technique (SIT) to control African malaria vectors in designated areas. The SIT relies on the sterilization of males before mass release, with sterilization currently being achieved through the use of ionizing radiation. This paper reviews previous work on radiation sterilization of Anopheles mosquitoes. In general, the pupal stage was irradiated due to ease of handling compared to the adult stage. The dose-response curve between the induced sterility and log (dose) was shown to be sigmoid, and there was a marked species difference in radiation sensitivity. Mating competitiveness studies have generally been performed under laboratory conditions. The competitiveness of males irradiated at high doses was relatively poor, but with increasing ratios of sterile males, egg hatch could be lowered effectively. Males irradiated as pupae had a lower competitiveness compared to males irradiated as adults, but the use of partially-sterilizing doses has not been studied extensively. Methods to reduce somatic damage during the irradiation process as well as the use of other agents or techniques to induce sterility are discussed. It is concluded that the optimal radiation dose chosen for insects that are to be released during an SIT programme should ensure a balance between induced sterility of males and their field competitiveness, with competitiveness being determined under (semi-) field conditions. Self-contained ⁶⁰Co research irradiators remain the most practical irradiators but these are likely to be replaced in the future by a new generation of high output X ray irradiators.     

Single-molecule anisotropy imaging

A novel method, single-molecule anisotropy imaging, has been employed to simultaneously study lateral and rotational diffusion of fluorescence-labeled lipids on supported phospholipid membranes. In a fluid membrane composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, in which the rotational diffusion time is on the order of the excited-state lifetime of the fluorophore rhodamine, a rotational diffusion constant, D(rot) = 7 x 10(7) rad(2)/s, was determined. The lateral diffusion constant, measured by direct analysis of single-molecule trajectories, was D(lat) = 3.5 x 10(-8) cm(2)/s. As predicted from the free-volume model for diffusion, the results exhibit a significantly enhanced mobility on the nanosecond time scale. For membranes of DPPC lipids in the L(beta) gel phase, the slow rotational mobility permitted the direct observation of the rotation of individual molecules characterized by D(rot) = 1.2 rad(2)/s. The latter data were evaluated by a mean square angular displacement analysis. The technique developed here should prove itself profitable for imaging of conformational motions of individual proteins on the time scale of milliseconds to seconds.     

Infrared mass spectrometric imaging below the diffraction limit

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS)1 is an established technique for the analysis of biological macromolecules. Its relative insensitivity to pollutants makes MALDI-MS very suitable for the direct analysis of biological samples. As such, it has facilitated great advances in the field of biomolecular imaging mass spectrometry. Traditionally, MALDI-MS imaging is performed in a scanning microprobe methodology.(2-4) However, in a recent study we have demonstrated an alternative methodology; the so-called microscope mode,(5) where the requirement for a highly focused ionization beam is removed. Spatial details from within the desorption area are conserved during the flight of the ions through the mass analyzer, and a magnified ion image is projected onto a 2D-detector. In this paper, we demonstrate how imaging mass spectrometry benefits from the microscope mode approach. For the first time, high-lateral resolution ion images were recorded using infrared MALDI at 2.94 microm wavelength. The ion optical resolution achieved was well below the theoretical limit of (light-) diffraction for the setup used, which is impossible to achieve in the conventional scanning microprobe approach.     

Confirmation of quantitative trait loci affecting fatness in chickens

In this report we describe the analysis of an advanced intercross line (AIL) to confirm the quantitative trait locus (QTL) regions found for fatness traits in a previous study. QTL analysis was performed on chromosomes 1, 3, 4, 15, 18, and 27. The AIL was created by random intercrossing in each generation from generation 2 (G₂) onwards until generation 9 (G₉) was reached. QTL for abdominal fat weight (AFW) and/or percentage abdominal fat (AF%) on chromosomes 1, 3 and 27 were confirmed in the G₉ population. In addition, evidence for QTL for body weight at the age of 5 (BW5) and 7 (BW7) weeks and for the percentage of intramuscular fat (IF%) were found on chromosomes 1, 3, 15, and 27. Significant evidence for QTL was detected on chromosome 1 for BW5 and BW7. Suggestive evidence was found on chromosome 1 for AFW, AF% and IF%, on chromosome 15 for BW5, and on chromosome 27 for AF% and IF%. Furthermore, evidence on the chromosome-wise level was found on chromosome 3 for AFW, AF%, and BW7 and on chromosome 27 for BW5. For chromosomes 4 and 18, test statistics did not exceed the significance threshold.     

Responses of trout gill ion transport systems to acute acidosis.

The response of rainbow trout Na+ and Cl- uptake systems to acute acidosis was tested by slow infusion of lactic acid into anaesthetized animals. Depression of blood pH by 0-4 pH unit had no effect on influx rates for either ion, and we conclude that gill ion uptake systems do not respond rapidly to blood pH changes.     

Strawberry odor, but not red color, enhances the sweetness of sucrose solutions

Several investigators have recently reported that odor and colorcan influence the sweetness of stimuli containing sucrose. Theseeffects were examined further by assessing the effect of redcoloring and strawberry odorant on the sweetness ratings ofaqueous solutions of sucrose. Two methods of olfactory stimulationwere used: (i) sip and spit, and (ii) swallowing the solutions.It was anticipated that swallowing the solutions would enhancethe olfactory effects by augmenting retronasal olfactory stimulation.The strawberry odor induced a small, but significant increasein sweetness for both the sip and spit and swallowing condition.There was a tendency for this effect to be more consistent andstable in the swallowing condition. Red coloring had no effecton sweetness.     

Analysing treatment means in plant tissue culture research

Many researchers set up an experiment, make measurements, do an analysis of variance, calculate the mean response for each treatment, and then try to decide if the treatment means are significantly different and why. Much too frequently, Duncan's multiple range test is used to test differences among means. It is only one of a number of techniques that can be used to examine treatment means. Some researchers are unaware of the different techniques and that the interpretation of the results of an experiment is strongly influenced by the technique used i.e. using two different techniques might produce two different interpretations of the results. Selection of the appropriate technique to use for a particular experiment depends upon the nature of the treatments and the objectives of the research. This paper discusses four techniques (ranking treatment means, multiple comparison procedures, fitting response models, and using contrasts to make planned comparisons) that can be used to examine treatment means and presents examples of the use of each one for plant tissue culture research.Abbreviations (IAA) indole-3-acetic acid - (IBA) indole-3-butyric acid - (NAA) naphthalene-acetic acid - (2,4-D) 2, 4-dichlorophenoxyacetic acid - (BA) benzyladenine - (PBA) tetrahydropyranylbenzyladenine - (2iP) 2 isopentenyl adenine - (2iPA) 2 isopentenyl adenosine Journal Paper J-12661 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project 2210.