RISK DETECTION IN INDIVIDUAL HEALTH CARE: ANY LIMITS?

Background: Biomedical science is producing an avalanche of data about risk factors, often with a small predictive value, associated with a broad diversity of diseases. Prevention and screening are increasingly moving from public health into the clinic. Therefore, the question of which risk factors to investigate and disclose in the individual patient, becomes ethically increasingly urgent. In line with Wilson and Jungner's public health‐related 10 principles for screening, it seems crucial to distinguish important from unimportant health risks. Aim: to explore the ways in which clinicians distinguish important from unimportant health risks. Methods: We interviewed 36 respondents (gastroenterologists and gynaecologists/obstetrics) in 5 focus group interviews and 15 open in‐depth interviews on their interpretation of what makes a health risk important. Results: Physicians primarily interpreted importance as the severity of the possible harm, less often its probability. Possibilities of prevention or reassurance strongly influenced their judgment on importance. Discussion: It is not likely that interpreting ‘important’ as ‘severe’ will help in differentiating meaningful from meaningless risk knowledge. A more fundamental change in our ways of dealing with risk may be called for. We discuss existing literature on resilience as an alternative way to deal with risk. Balancing prevention and risk reduction with resilience could be a fruitful direction.     

The influence of R:FR ratio on the growth, photosynthesis and rooting ability of Terminalia spinosa Engl. and Triplochiton scleroxylon K. Schum

Stockplants of the tropical hardwoods Terminalia spinosa Engl, and Triplochiton scleroxylon K. Schum were grown in a controlled environment under red:far-red (R:FR) ratios ranging from 0.5-3.1. In both species, rates of shoot height increment were higher (P < 0.05) under the low R:FR ratios as a result of increased internode elongation. In Terminalia spinosa , specific leaf area (SLA) was also significantly higher under lower R:FR ratios, values ranging from 175 to 210 cm² g^-1 in the 3.1 and 0.9 treatments respectively. No effect of R:FR ratio on SLA was recorded in Triplochiton scleroxylon. Pre-severance photo-synthetic rate, stomatal conductance and water-use efficiency were increased under the higher R:FR ratios in Terminalia spinosa , rates of photosynthesis ranging between 2.68-4.59 μmol m^-2 s^-1 in the 0.5 and 3.1 R:FR treatments respectively. Gas exchange rates of Triplochiton scleroxylon were unaffected by R:FR treatment. These contrasting responses to variation in R:FR ratio were associated with differences in rooting ability. In Terminalia spinosa , significantly higher percentage rooting was recorded in the cuttings from the 3.1 R:FR treatment than from 0.5, with values of 93.7% and 77.5% recorded respectively. R:FR ratio also affected rooting percentages of Triplochiton scleroxylon , but in this case, higher rooting percentages were recorded in the lower R:FR ratios, values ranging from 31.1–54.1% in the 3.0 and 0.5 R.FR treatments respectively. This difference in rooting response is attributed to the contrasting effects of R:FR ratio on the leaf and stem morphology of the two species. The implications of these results for stockplant management are discussed.     

The dynamics of predation on Gammarus spp. (Crustacea: Amphipoda)

Gammarus spp. (Crustacea: Amphipoda) are widespread throughout a diverse range of marine, freshwater and estuarine/brackish habitats, often dominating benthic macroinvertebrate communities in terms of both numbers and/or biomass. Gammarus spp. are the dominant macroinvertebrate prey items of many fish, whether as a seasonal food source or a year-round staple. Selective predation by fish on Gammarus spp. is often linked to parasitism and the body size of the prey. Gammarus spp. populations are under increasing threat from both pollution and replacement/displacement by introduced species. Loss of populations and species invasions/replacements could have significant impacts on native predator species if the predator(s) cannot successfully adapt their feeding patterns to cope with non-indigenous Gammarus prey species. Despite this, many fish predation studies do not identify Gammarus prey to species level. This lack of precision could be important, as Gammarus spp. exhibit wide variations in physiochemical tolerances, habitat requirements, abilities to invade and susceptibility to replacement. Although rarely acknowledged, the impacts of nonpiscean predators (particularly macroinvertebrates) on Gammarus prey species may frequently be stronger than those exerted by fish. A major aim of this review is to ascertain the current importance of Gammarus as a prey species, such that the implications of changes in Gammarus spp. populations can be more accurately assessed by interested groups such as ecologists and fisheries managers. We also review the dynamics of Gammarus spp. as prey to a diverse array of mammals, birds, amphibians, insects, flatworms, other crustaceans such as crabs and crayfish and, perhaps most importantly, other Gammarus spp.     

THE DEVELOPMENT OF CYTOLOGICAL THEORY IN THE OOMYCETES

1. Meiosis in the Oomycetes is gametangial. 2. The life-cycle of the Oomycetes is therefore haplobiontic, type B. 3. The gametangia are multinucleate prior to septation. Vegetative nuclear divisions may occur in the hyphae subtending the gametangia, but there is no evidence for such divisions occurring in the gametangial primordia nor is there any indication that nuclei may move out of the primordium against any cytoplasmic flow. 4. Some abortion of supernumerary nuclei probably occurs after the gametangium is cut off from the vegetative thallus by the septum. Meiosis then takes place. 5. The spindle of the first metaphase is almost certainly within a persistent nuclear membrane, but there remains some doubt as to whether this membrane persists to the second telophase in all Oomycetes. 6. In the higher Peronosporales, and possibly the Rhipidiaceae, meiosis is accompanied or preceded by zonation into the periplasm and ooplasm. Spindle orientation and the timing of zonation movements probably account for the differences in the number of presumptive oosphere nuclei recorded between many Peronosporales. In some Albuginaceae, at least, it is possible that only one nucleus completes the meiotic division, but this needs confirmation. 7. A smaller number of nuclei enter the male gametangium and undergo a more or less simultaneous meiosis. 8. Some variation in the pattern and degree of synchrony of meiotic division within and between gametangia occurs in different species. 9. Nuclear abortions may precede, accompany or follow meiosis, but only in a few instances (Pythium debaryanum, P. deliense, Phytophthora himalayensis, Aphanomyces laevis) does the male gametangium finally contain only a single gamete nucleus. 10. Cytoplasmic cleavage, involving the tonoplast and central vacuole of the oogonium, occurs after meiosis in the Saprolegniales, thus offering an alternative mechanism to zonation movements for the production of uninucleate oospheres. The presence (Edson, 1915; Patterson, 1927b; Murphy, 1918) or absence (Trow, 1901; Saskena, 1936) or an homologous central vacuole in the Pythiaceae is disputed. 11. Karyogamy must follow antheridial penetration in those species which are not agamospermous, but the degree of facultative agamospermy is unknown. The timing of karyogamy, as opposed to somatogamy, is apparently variable between and within species (Wager, 1899; Arens, 1929, Moreau & Moreau, 1935; McDonough, 1937; Flanagan, 1970; Win-Tin, 1972). There are a few indications that karyogamy may be precocious and other evidence that it may be considerably delayed, even after the oospore has achieved morphological maturity, and exceptionally until germination. 12. It would appear that the majority of the oospores of most Oomycetes eventually contain only one fusion or diploid nucleus, but there are exceptions (Albugo bliti, A. platensis, A. portulacae and Aplanopsis terrestris respectively) and without further study it would be unwise to assume that this is necessarily true even for closely related species. 13. Mitosis immediately following karyogamy is reported as occurring in some species of Albugo, but in most Oomycetes it is delayed until the period immediately preceding any cytoplasmic or morphological change at the start of germination. 14. The nuclear divisions of the germinating oospore are mitotic, but they may differ in the detailed morphology of the spindle apparatus or the degree of condensation of the chromosomes. 15. Interpretations of the cytology of the small nuclei of the Oomycetes have been profoundly influenced by the prevailing climates of scientific opinion. In particular, the development of studies of meiosis and the science of genetics on the one hand, and the appreciation of the polyphyletic origin of the fungi, especially the algal origins of the Oomycetes on the other hand, have necessitated a re-evaluation of much of the older literature.     

A new genus of the Verrucalvaceae (Oomycetes)

DICK. M. W., CROFT, B. J., MAGARF.Y, R. C, de COCK, A. W. A. M. & CLARK, G., 1989. A new genus of the Verrucalvaceae (Oomycetes) . A fungus, isolated from sugar cane in Queensland, Australia and causing the Poor Root Syndrome disease, is described and shown to be related to Verrucalvus and possesses verrucate oogonia containing plerotic oospores; it is placed in the Verrucalvaceae (Sclerosporales). On the basis of morphological and DNA studies the Verrucalvaceae has to be placed in the Saprolegniomycetidae. It follows that the order Sclerosporales (and also the Leptomitales) must be removed from the Peronosporomycetidae and placed in the Saprolegniomycetidae.     

Defensive behaviour of the wheat aphid,Schizaphis graminum (Rondani) (Hemiptera: Aphididae), against Coccinellidae

An account is given of the behaviour of the wheat aphid, Schizaphis graminum, in response to attacks by two coccinellid predators Scymnus morelleti and Exochomus concavus. Various responses are described and their influence on predator efficiency is investigated.