Detection and false-positive rates of maternal serum markers for Down syndrome screening according to maternal age in women over 35 years of age. A study of the agreement of eight dedicated software packages

Maternal serum markers for trisomy 21 screening (MSS) can be assayed in women ≥35 years in an attempt to reduce the need for invasive procedures and thereby avoid their side effects. Our objective was to compare, in women ≥35, eight different software packages dedicated to second trimester MSS, thus providing reliable data for patient counselling. A simulation study was carried out on 189 sera from women with Down syndrome fetuses and 11 962 sera from mothers of unaffected babies. The first step was to estimate the joint distribution of alpha-fetoprotein (AFP) and free beta-human chorionic gonadotrophin (β-hCG). The second step was to calculate trisomy 21 detection and false-positive rates for each software according to maternal age (35–45 years), using the usual 1:250 risk threshold. Agreement between software packages was measured using 2×2 kappa coefficients. Detection rates and false-positive rates increased with maternal age. Depending on the software, 57–71% detection rates were achieved at 35 years with 12–18% false-positive rates. At 45 years, 61–100% detection rates were achieved with 66–95% false-positive rates. Up to 39 years, all softwares were concordant (kappa coefficients >0.75). In the range 35–45 years, false-positive and detection rates increased substantially with maternal age and differences between software packages are observed. Copyright © 2002 John Wiley & Sons, Ltd.     

Earthquake-related chemical and radioactivity changes of thermal water in Kuzuluk-Adapazan,Turkey

The movements of the North Anatolian Fault Zone (NAFZ) caused two devastating earthquakes within an 87-day interval, epicentered on G?lcük-Izmit (17 August, 1999) and Düzce-Bolu (12 November, 1999). The Kuzuluk geothermal area (KGA) is located in the middle of the epicenters and the distance between the geothermal area and the fault zone is less than 5 km. Hot water samples were collected from two thermal boreholes that supply hot water to the Kuzuluk thermal complex. The water samples taken prior to and after earthquakes were analysed by Neutron Activation and Atomic Absorption Spectroscopy. Particularly, increase in total a and total beta activities, in the content of Pb, Cr, Ni, Cu and decrease in the content of Fe, Zn, Cd, Mn, and Co are significant. The highest values are 75, 35, 12 and 65 ppb for Pb, Cr, Ni and Cu, respectively. The lowest values are 45, 55, 15, 135 and 6 ppb for Fe, Zn, Cd, Mn and Co, respectively.     

The pollution status and the toxicity of surface sediments in Izmit Bay (Marmara Sea), Turkey

Izmit Bay is one of the most polluted and populated enclosed sea in Turkey. It has been the centre of industrial activities for the last 30 years. Seven major sources enter the bay waters along the north coastline of the bay. This investigation forms part of continuing ecotoxicology studies in the Izmit Bay designed to constrain and minimise the pollution caused by flourishing industry and a growing population. Sediments sampled from the mouths of the major discharges of Izmit Bay were analysed for their organic carbon, total polycyclic aromatic hydrocarbon (t-PAH) and trace inorganic element (Cd, Al, As, Pb, Hg and Cu) contents and compared with those found in the sediments from the reference station in the outer bay (in the Marmara Sea). The toxicity of sediments was determined in the bulk and elutriate samples by using algal (Phaeodactylum tricornutum) batch bioassays. Chemical data showed that the sediments collected from the inner sites of the bay have been contaminated with Cd, Hg, As and PAHs. Organic carbon contents were also found higher. All the major industrial discharges into the bay are now biologically treated but bioassays performed with bulk sediments revealed that the recent sediments are toxic to the microalgae throughout the bay. The results are consistent with the previous toxicity studies performed with the industrial discharges.     

In situ characterization of sulphur in gill-endosymbionts of the shallow water lucinid Codakia orbicularis (Linné, 1758) by high-pressure cryofixation and EFTEM microanalysis

In this study, Codakia orbicularis gill-tissues were cryo-fixed by using high-pressure freezing, a freeze substitution process and finally by cryo-embedding in Lowicryl. Ultrathin sections were then used for an EFTEM microanalysis. Results show that intracellular bacterial symbionts contain elemental sulphur in periplasmic vesicles as indicated by conventional TEM. When sulphur is temporarily depleted in the environment, such structures may act as energy sources for bacterial metabolism. Moreover, sulphate was detected in the cytoplasm of the bacterial symbionts, suggesting the oxidation of elemental sulphur, located in periplasmic granules, to sulphate (the final step in sulphur oxidation) by these chemoautotrophic bacteria. To assess the effects of host starvation on the bacterial sulphur content, adult individuals of C. orbicularis were maintained in starvation for 6 weeks in sterile artificial seawater depleted in sulphur. During starvation, both (1) the number of bacteria inside the bacteriocytes and (2) the number of periplasmic granules per prokaryotic cell decreased. The content of the remaining periplasmic granules had been modified to sulphate. This observation suggests that bacterial gill-endosymbionts used the elemental sulphur in their periplasmic granules as stored substrate for oxidation in order to produce energy in case of sulphur depletion.     

Do ovarian scars persist with age in all Cetaceans: new insight from the short-beaked common dolphin (<Emphasis Type="Italic">Delphinus delphis</Emphasis> Linnaeus<Emphasis Type="Italic">,</Emphasis> 1758)

The determination of reproductive status and the reconstruction of individual reproductive histories are central to many ecological studies. In cetaceans, it has been assumed that ovarian scars accumulate with age and provide a lifetime record of female reproductive history. If ovarian scars persist, the number of scars should increase with age after puberty. To test this, we examined age, reproductive status and ovarian scars from 187 short-beaked common dolphins (Delphinus delphis) from the eastern North Atlantic. The number of Corpus Albicans (CA) present in ovaries did not increase with age after age at sexual maturity (ASM), suggesting that ovarian scars are not persistent and that their number at any one time would be a function of rates of ovulation and healing, the latter being defined here as the resorption or disintegration of CA tissue. Since female mammals stop ovulating when pregnant, inferences about healing rates could be made by using pregnant females. Pregnant females had ca. 40% fewer scars than non-pregnant females. This suggests that most CAs would heal quickly, with a half-life of less than 1 year, although larger scars may persist longer. Therefore, counting CAs would have limited potential for reconstructing individual reproductive lifetime histories in the common dolphin. A reassessment of the use of ovarian scars to reconstruct individual life reproductive histories in cetaceans is suggested.     

Depth-related shift in life history strategies of a brooding and broadcasting deep-sea asteroid

Combining field and laboratory work, this study investigated the reproductive cycle, aggregative behavior, spawning periodicity, development and early growth of the sea star Henricia lisa living at bathyal depths off eastern Canada. Marked differences were found between individuals from ~1,300 and ~600 m deep. The former had a male biased sex ratio and an aperiodic reproductive cycle, whereas the latter displayed an equal sex ratio and a biannual breeding pattern. Furthermore, the maximum size was larger and female fecundity roughly five times higher in shallower compared to deeper populations. In the tanks, aggregative behavior was recorded twice a year during the summer and winter breeding periods. The onset of aggregations and spawning coincided with a temperature of 3–4°C. Males spawned first and females typically responded inside 30–60 min. Between 12 and 20 eggs were retained to be brooded under the arched arms of the female, whereas the remainder were broadcasted and developed without parental care. The fertilized eggs underwent a first cleavage after 12 h, reached the brachiolaria stage in 1 month, became juveniles within 3–4 months and reached ~ 4 mm in diameter after 14–17 months of growth. The embryos and juveniles developed at the same rate whether brooded or not, and development of winter cohorts was typically slower due to lower prevailing temperatures. This study of H. lisa provides the first evidence of lecithotrophy in a seasonally breeding deep-sea echinoderm and of brooding in a deep-sea asteroid.     

Territory ownership and familiarity status affect how much male root voles (Microtus oeconomus) invest in territory defence

Neighbour–stranger discrimination occurs when individuals respond with more aggression to strangers than to territorial neighbours—a phenomenon termed the “dear enemy phenomenon” (DEP). We investigated the DEP with male and female root voles (Microtus oeconomus Pallas 1776) using field dyadic arena tests conducted in enclosures where we could test for the effects of familiarity (familiar versus stranger), ownership (resident versus intruder status) and resource-holding potential (body mass) on territorial behaviours. The results showed that males put more effort into territorial defence than females, and males could discriminate between neighbours and strangers. In males, aggressiveness was influenced by a significant two-way interaction between treatment and ownership. Male residents were more aggressive towards stranger intruders than towards neighbour intruders, while male intruders were less aggressive towards stranger residents than towards neighbour residents. In females, neither treatment nor ownership status had a significant effect on aggressiveness. Familiar males performed more social behaviours but less non-social behaviours than stranger males. Furthermore, there was a clear dominance hierarchy between residents and intruders in stranger dyads, with the male territory holders dominating the intruder in pairwise interactions. To our knowledge, these results demonstrate for the first time DEP in a small mammal with a known pedigree and present the first evidence for “prior resident advantage” in voles. We argue that both ownership status and familiarity status affect how much an individual invests in territory defence. The benefits of neighbour–stranger discrimination for male root voles and the absence of neighbour–stranger discrimination in female root voles are discussed.     

Estimating parameters of neutral communities: from one single large to several small samples

The neutral theory of S. P. Hubbell postulates a two-scale hierarchical framework consisting of a metacommunity following the speciation-drift equilibrium characterized by the "biodiversity number" theta, and local communities following the migration-drift equilibrium characterized by the "migration rate" m (or the "fundamental dispersal number" I). While Etienne's sampling formula allows simultaneous estimation of theta and m from a single sample of a local community, its applicability to a network of (rather small) samples is questionable. We define here an alternative two-stage approach estimating theta from an adequate subset of the individuals sampled in the field (using Ewens' sampling formula) and m from community samples (using Etienne's sampling formula). We compare its results with the simultaneous estimation of theta and m (one-stage estimation), for simulated neutral samples and for 50 1-ha plots of evergreen forest in South India. The one-stage approach exhibits problems of bias and of poor differentiability between high-theta, low-m and low-theta, high-m solution domains. Conversely, the two-stage approach yielded reasonable estimates and is to be preferred when several small, scattered plots are available instead of a single large one.