Adaptation of an introduced host to an indigenous parasite

Introduction of striped bass to the west coast from the east coast of the U.S.A. provided the opportunity to study a recent host-parasite association in a marine system. An indigenous species of parasite was known to induce pathological changes in the introduced population. Because the west coast population has been in association with this pathogenic parasite more than 20 generations, we predicted that the host reaction of the west coast population would be less severe compared to that of the naive east coast stock of striped bass. This prediction was tested by conducting reciprocal infection experiments with east and west coast hosts and parasites. The group of west coast striped bass had a lower intensity of infection and exhibited less tissue damage compared to the group of east coast striped bass. We suggest that selection has acted only on the host and is driven by parasite-induced host mortality. This type of 1-sided selection is in contrast to present models of the evolution of host-parasite associations.     

How to immobilize an ant

Summary A method to immobilize ants or other small insects for marking using a vacuum pump is proposed.     

Censoring in an epidemic with an application to hemophilia-associated AIDS

In epidemiologic studies of infectious diseases, the times of infection may be known only up to an interval. A two-stage parametric regression model is proposed for the analysis of cohort studies during an epidemic in which the exact times of infection cannot be ascertained. The methods permit joint estimation of the effects of covariates both on the risk of infection and the risk of progression to clinical disease once infected. The methodology is applied to a cohort of hemophiliacs who were at risk of infection with the AIDS virus. It was found that hemophiliacs with severe Type A hemophilia were at highest risk of infection, and the risk of infection increased sharply in the early 1980s. Hemophiliacs who were over the age of 20 at infection were at higher risk of progression to AIDS than hemophiliacs who were under age 20. The estimate of the cumulative probability of developing AIDS within t years of infection (the incubation period distribution) for hemophiliacs over age 20 was 1 - exp(-.0021t2.516). Since follow-up in this cohort was restricted to about 10 years from infection, estimates of the incubation period distribution beyond 10 years depend on model extrapolation and should be interpreted cautiously.     

A monoclonal antibody recognizes an epitope common to an avian-specific nuclear antigen and to cytokeratins

X3, a monoclonal antibody of unusual specificity, is described. This antibody reacts with one or more cytokeratin polypeptides and also reacts with an avian (chicken, quail) nuclear antigen that appears to be present in all cell types (chicken) tested, although with variable staining pattern and intensity. This antigen is distinct from the cytokeratins but does have an epitope in common with this class of proteins. It disappears from the nucleus during the early stages of cell division and reappears during anaphase as a granular cytoplasmic structure. In late telophase the antigen is relocated in the nucleus. This antigen, which we have designated as avian-specific nuclear antigen (AVNA), is not associated with chromatin or ribonucleoproteins. From immunoblotting experiments on chicken fibroblast nuclei, AVNA is probably a complex composed of one or several polypeptides, one of which has a molecular weight of approximately 60 kD. The proteins were identified as nuclear matrix proteins rather than pore complex-lamina proteins by immunoblotting experiments on the purified nuclear matrix of chicken erythrocytes. The major polypeptide had a molecular weight of 60 kD and the minor polypeptide a molecular weight of 69 kD.     

When to refer an infertile mare to a theriogenologist

Most equine infertility cases can be solved with a methodical, thorough physical and reproductive examination and appropriate diagnostic laboratory aids. Repeated examinations may be needed in some cases to identify subtle anatomical abnormalities or irregularities between hormonal and physiological relationships of the reproductive tract. For pregnancy to occur, hormonal signaling must be exquisitely synchronized with physical changes of the reproductive tract and deposition of fertile semen in the uterus. Asynchrony of these events, infection, inflammation, previous trauma to the reproductive tract or "stress" can interfere with conception or maintenance of pregnancy. Infertile mares are presented for three common problems: (1) accumulation of intra-uterine fluid during or immediately after estrus; (2) long standing infection and/or chronic inflammation; or (3) irregular or no estrous cycles. By defining the problem, diagnostics can be chosen to determine the cause. Treatment protocols should be designed around the diagnosis and antibiotics, ecbolics or steroids should not be used indiscriminately. In all cases of mare infertility, semen quality needs to be determined to be satisfactory as a subfertile stallion bred to a subfertile mare greatly decreases the likelihood of pregnancy.     

Attempts to use the HPRT-assay as an automated short-term monitor for an acute exposure to mutagens

Attempts have been made to use the hypoxanthine-guanine-phospho-ribosyl-transferase-assay as a method for automated screening of agent-induced phenotypic variants of human peripheral lymphocytes reflecting 6-thioguanine resistance and assumed to indicate genotoxic action. Different protocols of the hypoxanthine-guanine-phospho-ribosyl-transferase-system were used in this study in order to investigate whether the system can be a candidate for a short-term test for a rapid and reliable identification of biological systems exposed to agents. The current protocols were based on: 1) fluoresceinated monoclonal antibodies against bromodeoxyuridine-DNA for labelling of 6-thioguanine-resistant human lymphocytes and direct flow-cytometric enumeration of bromodeoxyuridine-positive events and: 2) indirect flow-cytometric enrichment of 6-thioguanine-resistant cells labelled with ³H-thymidine followed by autoradiographic enumeration of positive events. Both the direct and the indirect enumeration method yielded similar results down to the range 10^–4 with respect to frequency of variants. For the less time-consuming direct enumeration method the resolution was limited due to non-specific binding of the antibody and false positives. It was, nevertheless, sufficient to score variants induced in vitro with the mutagens EMS, MMC and TT in the same range as e.g. that of cancer patients during and after chemotherapy or radiotherapy, or that of psoriasis patients during and after PUVA (8-methoxypsoralen and long range UV light)-therapy. We conclude that the direct enumeration protocol can be used for a rapid screening of so called outliers, but a more sensitive test, such as the more time-consuming enrichment protocol based on autoradiography, must be used in order to score variants in the range 10^–5–10^–6 Abbreviations ³H-TdR Tritiated thymidine - BrdU 5-2-bromodeoxyuridine - DNA Deoxyribonucleic acid - EMS Ethyl-methanesulphonate - FBS Fetal bovine serum - FITC Fluorescein Isothiocyanate - G₀ Cell cycle stage - G₁ Cell cycle stage - G₂ Cell cycle stage - HPRT Hypoxanthine Guanine Phospho Ribosyl Transferase - LI Labelling index - MMC Mitomycin C - PBL Peripheral blood lymphocytes - PBS Phosphate buffered saline - PHA Phytohemagglutinin - PI Propidium iodide - PUVA 8-Methoxypsoralen and long range UV-light therapy - RNA Ribonucleic acid - RPMI RPMI-1640 culturing medium - S_e Early S-stage in the cell-cycle - S_l Late S-stage in the cell-cycle - SCE Sister chromatid exchange - TG 6-Thioguanine - TT Thiotepa - UV Ultraviolet light - V_f Variant frequency     

Transition from an excitable to an oscillatory state in dictyostelium discoideum

Under conditions of starvation, populations of the amoebae Dictyostelium discoideum aggregate are mediated by chemical excitation waves of cAMP. Two types of waves can be observed, either spiral or circular-shaped ones. We investigate transitions from rotating spirals to circular shaped waves (target patterns). Two different experiments demonstrating this phenomenon are presented. In the first case a continuous transition from the spiral type pattern to target waves was observed at the later stages of aggregation. In the second case the transition was induced by annihilation of waves by a spatially homogeneous cAMP pulse. Instead of the originally present spiral waves, oscillating spots bearing target patterns emerged. On the basis of a model for Dictyostelium aggregation, we provide a theoretical explanation for such transitions. It is shown that cell density can be an effective bifurcation parameter. Under certain conditions, the system is shifted from the excitable to the oscillatory state while the frequency of oscillations is proportional to the square root of the cell density. Thus, the regions with the highest cell density during the early stages of the spatial rearrangement of the cells become pacemakers and produce target patterns. The analytic results were confirmed in numerical simulations of the model.     

Application of an interferometric biosensor chip to biomonitoring an endocrine discruptor

RecombinantE. coli ACV 1003 (recA::lacZ) releasing β-galactosidase by a SOS regulon system, when exposed to DNA-damaging compounds, have been used to effectively monitor endocrine disruptors. Low enzyme activity of less than 10 units/mL, corresponding to a μg/L (ppb) range of an endocrine disruptor (tributyl tin, bisphenol A,etc.), can be rapidly determined, not by a conventional time-consuming and tedious enzyme assay, but by an alternative interferometric biosensor. Heavily boron-doped porous silicon for application as an interferometer, was fabricated by etching to form a Fabry-Perot fringe pattern, which caused a change in the refractive index of the medium including β-galactosidase. In order to enhance the immobilization of the porous silicon surface, a calyx crown derivative (ProLinker A) was applied, instead of a conventional biomolecular affinity method using biotin. This resulted in a denser linked formation. The change in the effective optical thickness versus β-galactosidase activity, showed a linear increase up to a concentration of 150 unit β-galactosidase/mL, unlike the sigmoidal increase pattern observed with the biotin.     

Challenges to barcoding an entire flora

DNA barcodes are species‐specific genetic markers that allow taxonomic identification of biological samples. The promise of DNA barcoding as a rapid molecular tool for conducting biodiversity inventories has catalysed renewed efforts to document and catalogue the diversity of life, parallel to the large‐scale sampling conducted by Victorian naturalists. The unique contribution of DNA barcode data is in its ability to identify biotic material that would be impossible to classify using traditional taxonomic keys. However, the utility of DNA barcoding relies upon the construction of accurate barcode libraries that provide a reference database to match to unidentified samples. Whilst there has been much debate in the literature over the choice and efficacy of barcode markers, there has been little consideration of the practicalities of generating comprehensive barcode reference libraries for species‐rich floras. Here, we discuss several challenges to the generation of such libraries and present a case study from a regional biodiversity hotspot in southern Quebec. We suggest that the key challenges include (i) collection of specimens for rare or ephemeral species, (ii) limited access to taxonomic expertise necessary for reliable identification of reference specimens and (iii) molecular challenges in amplifying and matching barcode data. To be most effective, we recommend that sampling must be both flexible and opportunistic and conducted across the entire growing season by expert taxonomists. We emphasize that the success of the global barcoding initiative will depend upon the close collaboration of taxonomists, plant collectors, and molecular biologists.     

How to fine-tune an epigenetic switch

Arabidopsis does not flower in winter because FLC represses flowering genes, but prolonged cold exposure silences FLC, allowing flowering in spring. How do plants recalibrate this switch to adapt to different climates? Reporting in Science, Coustham et?al. (2012) found that tweaking a Polycomb target sequence may do the trick.     

Communications to an antenatal clinic.

When referring pregnant women to an antenatal clinic many general practitioners and midwives presented details of their care in an incomplete and inconsistent manner. As a result, hospital staff often had insufficient basic data from which to work. We recommend that those providing care decide what information they need and make the rationale of collecting this information the subject of a well-evaluated local education programme.