Prenatal ultrasonographic diagnosis of radial-ray reduction malformations

Radial-ray reduction malformations (RRRMs) may occur isolated or in association with other anomalies. The data of seven fetuses born with RRRMs were collected. Six fetuses had associated lethal abnormalities of the central nervous system, urogenital system, and/or heart, detected by ultrasound. In five cases, it was possible to establish the precise diagnosis, enabling an informed prognosis and subsequent genetic counselling. The diagnoses were: Edwards syndrome (n=3), VACTERL association (n=1), and Poland-Moebius-like complex (n= 1). In two cases, a complete diagnosis was not possible because of inadequate evaluation of these fetuses before and/or after birth. A proposal is given for the diagnostic approach for infants with RRRMs detected in the antenatal period by means of ultrasonography.     

溢油追踪报警器可行性研究

通过对专门设计的漂浮物在海洋中运动规律的分析，研究用来跟踪海上溢油漂移路线的可行性，从而，为溢油应急指挥中心的决策提供技术支持手段。     

Comparative genomics: methods and applications

Interpreting the functional content of a given genomic sequence is one of the central challenges of biology today. Perhaps the most promising approach to this problem is based on the comparative method of classic biology in the modern guise of sequence comparison. For instance, protein-coding regions tend to be conserved between species. Hence, a simple method for distinguishing a functional exon from the chance absence of stop codons is to investigate its homologue from closely related species. Predicting regulatory elements is even more difficult than exon prediction, but again, comparisons pinpointing conserved sequence motifs upstream of translation start sites are helping to unravel gene regulatory networks. In addition to interspecific studies, intraspecific sequence comparison yields insights into the evolutionary forces that have acted on a species in the past. Of particular interest here is the identification of selection events such as selective sweeps. Both intra- and interspecific sequence comparisons are based on a variety of computational methods, including alignment, phylogenetic reconstruction, and coalescent theory. This article surveys the biology and the central computational ideas applied in recent comparative genomics projects. We argue that the most fruitful method of understanding the functional content of genomes is to study them in the context of related genomic sequences. In particular, such a study may reveal selection, a fundamental pointer to biological relevance.     

疏浚物中有机锡的生物累积效应研究

于1998年6月在塘沽港附近水域采集贻贝（Mytilus edulis），经试验室培养驯化后作为试验材料，研究了三丁基氯化锡（TBTC0和三苯基氯化锡（TPTC）的累积效应及其对贻贝的毒性影响。结果表明，在累积效应试验中，TBTC及TPTC对贻贝的半致死浓度LC50分别为3．5μg/dm^3和5．0μg/dm^3，当TBTC浓度达2．0μg/dm^3时，贻贝的成活率开始降低，实验还表明，TPT对贻贝的毒性效应与TBT相近。     

Portrait of an Asian stalk-eyed fly

Diopsid flies have eyes set on stalks which are in some cases so long that the distance between the eyes exceeds the body length. These conspicuous structures have given rise to much speculation about their adaptive value, but there are very few actual observations by which to judge these hypotheses.Cyrtodiopsis whitei Curran lives in the tropical rainforest of Malaysia. We describe a number of aspects of its morphology and biology, some functional properties of the eye, and the ritualized fights between males, by which harems are acquired. The evolutionary significance of the eyestalks is discussed: they represent structures subjected to a double selection pressure; they are an adaptation by which a sensory system is better matched to the special problems encountered in a densely structured habitat (in that the field of view is extended and the ability to estimate distance and size and to identify objects at a large distance is improved), also they act as key stimulus for species recognition and as releaser for intraspecific behaviour.     

A unique strategy of host colony exploitation in a parasitic ant: workers of<Emphasis Type="Italic"> Polyrhachis lama</Emphasis> rear their brood in neighbouring host nests

The formicine ant Polyrhachis lama is a social parasite, exploiting its ponerine host ant species Diacamma sp. In most social parasitic associations, the parasitic species are closely related to their host species group, evolving directly from independent ancestors of the host species. However, in the Polyrhachis lama–Diacamma sp. association, the associated species belong to different ant subfamilies. Based on preliminary field surveys, we had presumed that P. lama might have given up its reproductive division of labour, i.e. workers would be able to produce males as well as workers and females parthenogenetically. In this study, this hypothesis was disproved: Polyrhachis lama workers cannot be fertilized and are only able to produce males. In the host–parasite association originating from nests possessing a P. lama queen, workers penetrate surrounding Diacamma sp. nests, carrying brood for rearing within these satellite nests. In this peculiar way, a single P. lama colony is able to exploit several Diacamma sp. colonies simultaneously.     

The influence of serum screening on the amniocentesis rate in women of advanced maternal age

We investigated the effect of maternal serum screening on the amniocentesis (AC) rate in women of advanced maternal age. The AC rate after maternal serum screening was compared in two groups of women with a singleton pregnancy, 855 women of 30–35 years and 98 of 36 years and older. In our population, 34·1 per cent of the women of 36 years or older were ‘screen-positive’ for Down syndrome. Only 41·2 per cent of these women chose to undergo AC as opposed to 88·2 per cent in the younger age group. Within the older age group, the tendency to avoid AC increased with increasing age. Maternal serum screening led to a significant decrease in the AC rate in the older women. In this group, a comparison between the ‘a priori’ and the calculated risk might have had more influence on the decision to undergo AC than being screen-positive or screen-negative as such. We conclude that maternal serum screening had a major effect on the AC rate in women of advanced maternal age. This is of importance in a society in which the average maternal age is steadily increasing.     

Feeding ecology of the three juvenile phases of the spiny lobster<Emphasis Type="Italic"> Panulirus argus</Emphasis> in a tropical reef lagoon

The three juvenile phases of the spiny lobster Panulirus argus (algal phase: 5-15 mm carapace length, CL; postalgal phase: 15-45 mm CL, and subadults: 45-80 mm CL) occur in the reef lagoon at Puerto Morelos, Mexico. The algal phase abounds in this lagoon, which is covered by extensive seagrass-algal meadows, but the density of postalgal and subadult juveniles is low, owing to the scarcity of crevice-type shelters suitable for these phases. The feeding ecology of the three juvenile phases was investigated to examine whether spatial or temporal differences in food intake, diet composition, or nutritional condition occurred among phases and could partially account for the low abundance of the larger juveniles. Juveniles were collected by divers at night, from January to November 1995, throughout the mid-lagoon and back-reef zones. Percent stomach fullness, relative weight of the digestive gland (RWDG, an index of nutritional condition), percent frequency of occurrence and percent volume of food categories in the diet were compared between sexes, juvenile phases, molt stages (postmolt, intermolt, premolt), seasons, and sampling zones (mid-lagoon and back-reef zones). Significant differences in stomach fullness occurred only among molt stages, mainly because postmolt individuals had emptier stomachs. The main food categories in all juvenile phases were crustaceans (mostly hermit crabs and brachyurans) and gastropods, but the food spectrum was wide, including many other animal taxa as well as plant matter. In June 1995, the epibenthic macrofauna was sampled in five sites in the lagoon that differed in their amount of vegetation. The most abundant taxa in all sites were decapods and gastropods, but density and diversity measures showed that the distribution of these potential prey taxa for juvenile P. argus was rather patchy. Diet overlap in juvenile lobsters was high between sexes, juvenile phases, sampling zones, seasons, and molting stages, indicating that all juveniles fed on the same general food categories throughout time. The only factor that affected the RWDG was the juvenile phase. RWDG was significantly lower in subadults than in algal and postalgal phases, suggesting a poorer nutritional condition in the largest juveniles. This may be related to the scarcity of suitable shelters for large juveniles throughout the lagoon, which may preclude subadults from exploiting food resources in areas of the lagoon where shelter is limited.