Amniotic fluid digestive enzymes: Diagnostic value in fetal gastrointestinal obstructions

The diagnostic value of amniotic fluid gamma-glutamyl-transpeptidase (GGTP) and intestinal alkaline phos-phatase (iALP) was evaluated in 55 patients who underwent amniocentesis for karyotyping because fetal gastric or small bowel dilatation had been detected by ultrasound. Gastrointestinal malformation was confirmed in 46 cases and there was no gastrointestinal anomaly in nine cases. Prenatal ultrasound was suggestive of gastroduodenal dilatation in 34 cases (group I) and small bowel dilatation in 21 cases (group II). In group I, amniotic fluid GGTP above the 99th percentile was 71 per cent sensitive and 100 per cent specific for a true anatomical defect of the digestive tract (mainly duodenal atresia). In group II, high levels of GGTP and/or iALP were 69 per cent sensitive and 83 per cent specific for a fetal digestive tract anomaly. In other words, when digestive tract dilatations were diagnosed by prenatal sonography, abnormal amniotic fluid enzyme activities were strongly suggestive of such an anomaly, the possibility of which was not precluded by normal amniotic fluid iALP and GGTP activities. But amniotic fluid digestive enzyme activities do not help in defining the prognosis.     

Wave action and competitive interaction between the invasive mussel Mytilus galloprovincialis and the indigenous Perna perna in South Africa

On the south coast of South Africa, the invasive alien mussel Mytilus galloprovincialis shows partial habitat segregation with the indigenous mussel Perna perna. P. perna predominates in the lower mussel zone and M. galloprovincialis in the upper zone, with mixed beds where the two overlap. We examined competitive interactions between these species by translocating mussels into small plots at high densities. Treatments involved different combinations of species and densities placed in each zone. Mortality was monitored regularly and at the end of each experiment, growth and condition index were measured. The experiment was attempted three times. The first two attempts were disrupted by wave action, especially winter storms, but provided information on species-specific effects of wave action. In experiment one, wave induced mortality decreased from a mean for both species of approximately 90% on the low shore to ca. 50% on the high shore, and was 15–30% lower for P. perna than M. galloprovincialis in each zone. In experiment two, M. galloprovincialis mortality was not affected by zone (Kruskal–Wallis test, P > 0.05), but was higher than P. perna mortality in the low zone (P < 0.05). P. perna survival was significantly (P < 0.05) lower on the high than mid and low zones, apparently due to the effects of greater emersion. Condition index showed a similar pattern, being lowest in the low zone for M. galloprovincialis and in the high zone for P. perna (3-way ANOVA, P < 0.05). Growth rates were fastest for both species in the low zone (Kruskal–Wallis, P < 0.05 in both cases). The third experiment was run for 12 months in the low zone only and provided evidence of intraspecific competition for P. perna and of interspecific competition. Condition was significantly greater for P. perna in all treatments (2-way ANOVA), as was growth (Kruskal–Wallis P < 0.05). Significant treatment effects indicated that P. perna had a negative effect on M. galloprovincialis survival (Kruskal–Wallis, P < 0.05). Again wave action was important; by the end of the experiment all mussels had been removed from plots stocked only with M. galloprovincialis. Thus P. perna improves survival of M. galloprovincialis on the low shore in the short term, by providing protection against wave action, but excludes it competitively in the longer term. The results show that partial habitat segregation is likely to be a permanent feature on the south coast, with M. galloprovincialis unable to dominate the low shore due to the effects of waves and competitive exclusion by P. perna. This study is the first attempt to examine the mechanisms of interaction between invasive and indigenous marine mussel species and provides evidence of the importance of environmental conditions in the mediation of this interaction.     

Human carcinogenesis by arsenic

Arsenic is one of the few human carcinogens for which there is not yet a reliable animal cancer model. As such, the classification of arsenic as a carcinogen is based upon data derived from human epidemiologic studies. Although the mechanisms of action of arsenic as a toxic agent have been known for many years, the inability to produce cancer with arsenic in laboratory animals has confounded the operational characterisation of arsenic as initiator, promoter, complete carcinogen, or cocarcinogen for humans. Arsenic is clearly a genotoxic agent that induces chromosomal aberrations, micronuclei and sister chromatid exchange in mammalian cells as well as neoplastically transforms Syrian hamster embryo cells; however, it is not a classical point mutagen. This paper reviews some of the scientifically based issues relating to arsenic and risk assessment.     

Vocal interactions in common nightingales (<Emphasis Type="Italic">Luscinia megarhynchos</Emphasis>): males take it easy after pairing

Seasonal patterns of bird song have been studied intensively with a focus on individual males. However, little is known about seasonal patterns of singing during vocal interactions between males. Vocal interactions have been shown to be important in sexual selection as males may signal aspects of motivation or quality. Here, we investigated in nightingales (Luscinia megarhynchos) whether a male’s behaviour in vocal interactions at different stages of the breeding season is influenced by its mating status. We examined how males that differ in their subsequent mating success respond to a non-interactive, nocturnal playback presented during the period of mate attraction and subsequently during the egg-laying period. We found that mated males overlapped fewer songs and had a lower song rate during the egg-laying period compared to their responses during the mate-attraction period, whereas unpaired males did not vary in their responses between the two periods. Our results suggest that mating status is a key factor affecting singing behaviour in vocal interactions and that a time-specific singing pattern like song overlapping is used flexibly during vocal interactions. Because song overlapping is thought to be a signal of aggression in male–male vocal interactions, it seems that males vary the level of aggression in vocal interactions according to their mating status and to the stage in the breeding season.     

Asymmetric sexual conflict over parental care in a biparental cichlid

Theoretical models predict that parents should adjust the amount of care both to their own and their partner’s body condition. In most biparental species, parental duties are switched repeatedly allowing for repeated mutual adjustment of the amount of care. In the mouthbrooding cichlid Eretmodus cyanostictus, terms are switched only once with females taking the first share. The timing of the shift of the clutch between mates strongly determines both partners’ brooding period and thereby their parental investment. Females signal their readiness to transfer the young several days before the male finally takes them, suggesting sexual conflict over the timing of the shift. In a lab experiment, we reduced the body condition of either the female or the male of a pair to test whether energy reserves affect the timing of the shift and whether female signalling behaviour depends on energetic state. Males with a lowered condition took the young later and incubated for a shorter period, which prolonged the incubation time of their female partners. When female condition was lowered, female and male incubation durations remained unchanged, although females signalled their readiness to shift more intensely. Our results suggest that males adjust their parental investment to own energy reserves but are unresponsive to their mate’s condition. Females appear to carry the entire costs for the male’s adjustment of care. We propose that intrinsic asymmetries in the scope for mutual adjustment of parental investment and the costs of negotiation crucially influence solutions of the conflict between sexes over care.     

Partitioning studies of coal-tar constituents in a two-phase contaminated ground-water system

Organic compounds derived from coal-tar wastes in a contaminated aquifer in St. Louis Park, Minnesota, were identified, and their partition coefficients between the tar phase and aqueous phase were determined and compared with the corresponding n-octanol/water partition coefficients. Coal tar contains numerous polycyclic aromatic compounds, many of which are suspected carcinogens or mutagens. Groundwater contamination by these toxic compounds may pose an environmental health hazard in nearby public water-supply wells. Fluid samples from this aquifer developed two phases upon settling: an upper aqueous phase, and a lower oily-tar phase. After separating the phases, polycyclic aromatic compounds in each phase were isolated using complexation with N-methyl-2-pyrrolidone and identified by fused-silica capillary gas chromatography/mass spectrometry. Thirty-one of the polycyclic aromatic compounds were chosen for further study from four different classes: 12 polycyclic aromatic hydrocarbons, 10 nitrogen heterocycles, 5 sulfur heterocycles, and 4 oxygen heterocycles. Within each compound class, the tar/water partition coefficients of these compounds were reasonably comparable with the respective n-octanol/water partition coefficient.     

Mercury transfer from fish carcasses to scavengers in boreal lakes: the use of stable isotopes of mercury

Scavengers play an important role in the flow of energy, matter and pollutants through food webs. For methylmercury (MeHg), which biomagnifies along food chains, the movement of this metal from fish carcasses to aquatic scavengers has never been demonstrated. We measured the transfer of MeHg from fish carcasses to scavenging leeches in two lakes and in the laboratory. The results of a field experiment indicated that leeches were attracted to fish carcasses and that their Hg concentrations increased by as much as a factor of 5 during the time that Hg-rich fish were available for consumption. Under controlled conditions, we exposed leeches to (202)Hg-labelled fish that had been marked in situ following a whole lake (202)Hg addition. Leeches rapidly accumulated Hg from carcasses, and within two weeks assumed the isotopic signature of the carcasses. Necrophagous invertebrates could therefore return Hg from fish carcasses to other trophic levels in lakes.     

Oryzalin fate and transport in runoff water in Mediterranean vineyards

An experimental study was conducted in a 91.4-ha Mediterranean vineyard catchment in southern France to characterize the fate and transport of oryzalin in runoff water and thus to assess the risk of contamination of surface waters. Oryzalin concentrations in soil were monitored on two fields, one no-till and one tilled from March 1998 to March 2000. Concentrations in solution and on solid phase of runoff water were measured at the outlets of both fields and the catchment. The droughts in the two summer periods reduced the dissipation of oryzalin and increased its field half-life up to 35 days. Consequently, oryzalin was detected throughout the year in runoff water, with maximum dissolved concentrations > 600 microg l(-1) at the field scale. Oryzalin transport essentially occurred in solution. At the no-till field, seasonal losses were 2.29% and 1.89% of the applied amount in 1998 and 1999, respectively. The corresponding values at the tilled field were 1.56% and 0.29%, since tillage reduced total losses by reducing surface runoff. At the catchment scale, oryzalin concentrations were smaller than those at the field scale, due to dilution effects and staggering of application. Large part of the overland flow from the fields reinfiltrated in the ditches before reaching the outlet of the catchment. As a result, seasonal oryzalin losses were <0.2% of the applied amount.     

Storage mediums affect metal concentration in woodlice (Isopoda)

Terrestrial invertebrates are becoming widely established as tools to assess heavy metal pollution at contaminated sites. A practical and time saving method to sample terrestrial invertebrates consist of pitfall traps, often filled with a 4% formaldehyde solution and some detergent. The reliability of metal concentrations based on organisms captured and stored in this solution might however be questioned and we therefore tested the effect of formaldehyde on Zn, Cu, Cd and Pb concentration experimentally in three isopod species. Our results showed that in many cases, significant decreases in Cu concentrations compared to animals stored in a freezer were observed that could be as high as 40%, while Zn, Cd and Pb concentrations increased. A regression analysis of individual dry weight on individual size revealed that formaldehyde decreases the dry weight substantially and in that way causes increased measurements of Zn, Cd and Pb concentrations. We conclude that pitfall traps with formaldehyde should better not be used to collect animals in which concentrations of heavy metals or other toxic substances will be determined.     

Occurrence and congener profiles of polybrominated diphenyl ethers (PBDEs) in environmental samples from coastal British Columbia, Canada

Environmental levels and detailed congener profiles (31 congeners and 3 coeluting congener groups) of polybrominated diphenyl ethers (PBDEs) were assessed in a number of biota samples taken over a large geographic range covering harbours and industrial sites on Canada's West Coast. Additionally, PBDE congener profiles were determined using semipermeable membrane devices (SPMDs) deployed in the Fraser River, the river in Western Canada with the largest industrial activity. PBDE levels detected in biota were between 4 and 2300 ng/g lipid and these levels were compared with those reported in selected European biota to provide a wider perspective on PBDE contamination on Canada's West Coast. Thirteen-congener PBDE patterns in the environmental samples were examined using principal component analysis (PCA), and additionally, comparisons were made between the PBDE profiles in the sample groups and commercially used PBDE technical mixtures (e.g., Bromkals) on a percent composition basis. PCA on congener specific data revealed that PBDE patterns are remarkably similar over a wide geographical range in Western Canada, however, the general pattern in environmental samples varies significantly from those of the predominant technical mixtures. Finally, correlations between PBDE and other persistent and toxic co-occurring contaminants found in Dungeness crab were determined.