First-trimester free beta (hCG) screening for Down syndrome

Maternal serum free beta (hCG) levels are elevated (median 2·20 MOM) in the first trimester of pregnancy in 38 Down syndrome cases as compared with appropriate controls. This observation may form the basis for its use as a marker in screening for Down syndrome in the first trimester. Altered levels of the free beta analyte are observed in pregnancy conditions or complications other than Down syndrome.     

Attitudes of women of childbearing age towards prenatal diagnosis in Southeastern France

The objective of this study was to explore women's attitudes towards prenatal diagnosis of trisomy 21 and to examine some of the factors possibly responsible for these attitudes before implementing in real practice serological screening of pregnant women at risk for trisomy 21. We carried out a telephone survey on a representative sample of women who had recently had a normal livebirth delivery in the Marseille district in 1990. The participation rate was 80 per cent and the average age of the mothers was 28-9 years. Among the 514 women interviewed, 78 per cent stated that they would ask for an amniocentesis for a 1 per cent risk of trisomy 21 at their next pregnancy. When adjusting for confounding factors, the decision to have or not to have an amniocentesis was found to depend not only on the women's attitude towards induced abortion, but also on their understanding of the risk involved and on the social context (knowing a handicapped child, discussion with the father). It also depended on the women's age and on what they knew about amniocentesis from the medical point of view. The risk of miscarriage can influence a woman's choice but this objection was not found to affect the women's decisions significantly in our survey. The data showed the existence of a high potential demand for fetal karyotyping.     

巴西圣保罗州莫日-瓜苏河流流域中的汞:根据210Pb测年剖面估计的沿海泻湖与河流贡献之间的联系

引言 莫日-瓜苏河位于纳斯吉拉斯州,海拔高1450m.流淌470km后,该河流注入圣保罗州的帕尔杜河.其流域总面积为1400km2,其中有86%位于圣保罗州,包括一个工业化地区[1].     

Costs and benefits of subordinate queens in colonies of the ant,<Emphasis Type="Italic"> Leptothorax gredleri</Emphasis>

Queens of some species of social insects form dominance hierarchies in which only the top-ranking individual reproduces. Such unequal partitioning of reproduction can be stable when subordinate queens increase their inclusive fitness indirectly by helping to rear a related dominant queen's offspring. We investigated whether subordinate queens of the ant, Leptothorax gredleri, affect the reproductive success of the dominant queen. In laboratory colonies with two queens, first eggs were laid approximately 20 days later than in colonies with a single queen, presumably due to aggressive competition among nestmate queens. Nevertheless, two-queen colonies produced on average more brood than one-queen colonies, although egg laying was completely or almost completely monopolized by one single queen. The presence of a subordinate queen therefore appears to increase the productivity of the dominant.     

Wax perception in honeybees: contact is not necessary

In social insects, much progress has been made in identifying variations in the cuticular signatures of sexes, castes, kin and reproductive status. In contrast to this, we still do not know how the receivers perceive these recognition cues. This study was designed to investigate whether honeybees use contact-chemosensory or olfactory sensilla to perceive wax components. To answer this question in a behavioral assay, we combined classical conditioning of the proboscis extension reaction and a recently established method using zinc sulfate to selectively block antennal contact-chemosensory sensilla. Comparison of the responses to sucrose, wax and geraniol before and after antennal zinc sulfate treatment revealed that the sucrose response is lost after treatment but the responses to wax and geraniol are maintained. As sucrose is perceived by the contact-chemosensory sensilla, the retention of the wax response indicates that contact-chemosensory sensilla are not necessary for wax perception.     

Effect of complexation by natural phytoplankton exudates on the accumulation of cadmium and copper by the haptophyceae Cricosphaera elongata

The accumulation of cadmium and copper by Cricosphaera elongata is determined in the absence and presence of natural phytoplankton exudates. The concentrations of metals accumulated increase with increasing concentrations of metals in the medium. Organic substances liberated into the culture medium by C. elongata are able to decrease the amounts of metals taken up.     

Chemically mediated interactions between the red algaPlocamium hamatum (Rhodophyta) and the octocoralSinularia cruciata (Alcyonacea)

Interactions between the red algaPlocamium hamatum J. Agardh (Rhodophyta) and other benthic organisms including the alcyonacean soft coralSinularia cruciata (Tixier-Durivault) were investigated on an inshore fringing reef environment in whichP. hamatum was the dominant large fleshy alga. Field observations of sessile reef organisms including octocorals and sponges living in close proximity toP. hamatum revealed that varying degrees of tissue necrosis were suffered by the invertebrates when in physical contact with the alga. In order to establish whether the chemical constituents of the alga, especially chloromertensene, played a role in this necrosis, manipulative field experiments were carried out in the Pelorus Channel, Palm Island group (18°34S; 146°29E), North Queensland, Australia, in November and December 1988. The first experiment involved the relocation of healthy plants and soft corals into contact and non-contact situations on a mesh grid. In all cases of contact betweenP. hamatum andS. cruciata, the soft coral suffered tissue necrosis (n=6,p=0.0022). The second experiment had the same design, but involved the use of artificial plants both uncoated and coated with natural levels of chloromertensene, in contact withS. cruciata. In all cases of contact with coated treatments, necrosis was observed inS. cruciata (n=4,p=0.025). In cases where uncoated artificial fronds were placed in contact with soft corals,S. cruciata showed minor abrasion effects, but no appreciable necrosis. Coated treatments were not fouled by epiphytes during the experiment and were not consumed by predators. Uncoated treatments were rapidly reduced in size by predation and any remaining material was biofouled. These experiments thus demonstrated that the deleterious effects observed in soft corals in the field were caused by contact with the algaP. hamatum, that these effects were indeed chemically mediated by chloromertensene, and that physical contact without chemical intervention caused no such deleterious effects. This is the first experimental evidence which conclusively demonstrates allelopathy between an alga and other marine organisms and identifies the compound responsible for the observed allelopathic effects.     

Complex host marking in the cabbage root fly

Summary. The cabbage root fly marks an oviposition site with two different chemical messages. Plants that were exposed to ovipositing flies are less acceptable than control plants, while sand particles that were closely associated with an actual oviposition site stimulate oviposition. By combining the information from these opposing messages, the cabbage root fly may be able to optimise the size of its egg clusters in relation to the food available for the larvae. The findings might account for the aggregated oviposition observed in this species.