First-trimester amniotic fluid and extraembryonic coelomic fluid acetylcholinesterase electrophoresis

Acetylcholinesterase (AChE) gel electrophoresis was performed on samples of amniotic fluid and extraembryonic coelomic fluid obtained by high resolution transvaginal ultrasound-guided amniocentesis from 38 women between 8 and 12 weeks of pregnancy. AChE was positive in 33 per cent (12/36) of the amniotic fluid samples; the percentage of positive results decreased as gestation advanced. AChE was positive in 32 per cent (9/28) of the extraembryonic coelomic fluid samples. In 81 per cent (21/26) of matched samples, the AChE results were identical in the two fluids. Amniotic fluid and extraembryonic coelomic fluid AChE electrophoresis cannot be used to diagnose neural tube defects prior to 12 weeks of gestation.     

Prenatal demonstration of a cervical myelocystocele

Myelocystocele is a rare spinal cord disorder and has not been described prenatally. We report a case in which prenatal ultrasound and magnetic resonance imaging (MRI) demonstrated a posterior cervical mass which was initially thought to be a meningocele or an atypical cystic hygroma. Surgery performed at 1 day of age showed this to be a myelocystocele. Therefore, the differential diagnosis of an extracranial cystic mass in the posterior cervical region should be expanded to include myelocystoceles.     

Nitrate uptake in marine phytoplankton: Energy sources and the interaction with carbon fixation

Field studies of whole natural phytoplankton communities from Knight Inlet, B. C., Canada and laboratory cultures of the diatom Skeletonema costatum indicate inorganic carbon fixation may be temporarily suppressed following 10 to 15% enrichment with NO ₃ ^- or NH ₄ ⁺ . (This effect is suggested to be due to competition between inorganic carbon and nitrogen for adenosine triphosphate (ATP), and is reduced when chlorophyll a is increased intracellularly after 6 to 8 h.) Results imply that the source of ATP for nitrate uptake is primarily from Photosystem I (cyclic photophosphorylation) in the presence of light. It would appear that a transient nutrient-adaptive response occurs upon addition of extracellular nitrogen.     

The association of female kin in the arctic ground squirrel Spermophilus parryii

Summary The association of kin in arctic ground squirrels (Spermophilus parryii) was studied near Haines Junction, Yukon Territory, during the summers of 1977, 1978, and 1979. Males dispersed in this population, thus only females were likely to live near relatives.Close female kin (sisters, mothers/daughters) had greater overlap of home ranges and interacted more amicably and less agonistically than did less closely related females. Closely related females clumped their young at emergence, whereas more distantly related females did not; there was little indication of clumping of pre-emerged young. The overlap of home ranges of distant relatives (known genetic relatives that had not associated in a natal burrow) was intermediate to that of close relatives and non-relatives. The types of interactions between distant relatives were more similar to those between non-relatives than between close relatives.I conclude that female arctic ground squirrels exhibit nepotism. Females may benefit from associations with relatives by sharing watching for predators once juveniles become conspicuous. Male arctic ground squirrels commit infanticide and several females may be more effective at protecting their young from infanticidal males than females living alone. I suggest that clumping of young by close relatives may provide a mechanism allowing distantly related females to identify each other.Address for offprint requests     

The behavioural basis of a species replacement: differential aggresssion and predation between the introduced Gammarus pulex and the native G. duebeni celticus (Amphipoda)

Previous studies have shown that differential predation by males on moulted female congenerics may be largely responsible for the elimination and replacement of the native Irish freshwater amphipod Gammarus duebeni celticus by the introduced G. pulex. Predation of moulted females occurs both shortly after their release from precopulatory mate-guarding and whilst they are being guarded by their mates. In the present study, two hypotheses concerning the underlying cause(s) of the differential predation pattern are tested. Firstly, female G. d. celticus may be more vulnerable to predation than female G. pulex due to the former being released from precopula guarding with the new exoskeleton in a less hardened state. Secondly, G. pulex may be an inherently more aggressive species than G. d. celticus during predatory interactions over guarded females. The first experiment indicated that differential predation was not mediated by species differences in the state of the female exoskeleton at the time of release from precopula by guarding males. The second experiment, however, showed that male G. pulex were significantly more aggressive than male G. d. celticus in attacking both guarding male congenerics and guarded moulted female congenerics. In addition, in defence against predatory attacks, paired male and female G. pulex were significantly more aggressive than paired male and female G. d. celticus. These differences in aggressive behaviour led to a significantly higher frequency of predation on G. d. celticus females than on G. pulex females, and also explains this finding in previous studies. It is concluded that differential predation due to differences in aggressive behaviour may explain the pattern of replacement between these species.     

In-situ partitioning of butyltin compounds in estuarine sediments

The in-situ solid/pore-water partitioning of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) was determined for an estuarine sediment profile collected from a commercial marina. Total butyltin levels exceeded sediment quality guideline values, and were 220-8750 microg/kg for TBT, 150-5450 microg/kg for DBT and 130-4250 microg/kg for MBT. Pore-water butyltin concentrations ranged from 0.05 to 2.35 microg/l for TBT, 0.07-3.25 microg/l for DBT, and 0.05-0.53 microg/l for MBT. The partitioning of butyltin compounds between the sediment solid-phase and pore-water was described by an organic carbon normalised distribution ratio (D(OC)). The observed D(OC) values were similar for TBT, DBT and MBT, and were 10(5)-10(6) l/kg. Values for the Butyltin Degradation Index (BDI) were larger than 1 at depths greater than 10 cm below the sediment/water-column interface. This indicates that substantial TBT degradation has occurred in the sediments, and suggests that natural attenuation may be a viable sediment remediation strategy.     

Snapping turtles - a biological screen for PCB's

Snapping turtles are capable of storing extremely high concentration of organochlorine compounds in their fat without any apparent detrimental effect. This tolerance, to high bioconcentration, permits a wide gradation between the extremes in pollution levels and facilitates the detection of extremely toxic substances present in trace amounts. Consequently snapping turtles provide an excellent biological screen for these compounds.     

Evaluation of sequentially-coupled POP fluxes estimated from simultaneous measurements in multiple compartments of an air-water-sediment system

Bulk atmospheric deposition fluxes, air-water exchange fluxes, particle settling fluxes out of the upper water column, sediment trap fluxes in deep waters, and sediment burial fluxes of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in the Koster Fjord, eastern Skagerak, on the Swedish west coast. The aim of the study was to compare the magnitude and direction of the compound fluxes in the system in order to diagnose key fate processes. The PCB and PAH fluxes via net atmospheric deposition, settling particles out of the surface and through deep waters, as well as into the accreting underlying sediments were shown to be remarkably similar, agreeing within a factor of a few for any given target compound. Fluxes of all PCB and PAH target compounds remained fairly constant with water column depth. Thus there was no evidence for net desorption from sinking particles. The net unidirectional and near balancing of vertical fluxes suggests a net transport of PCBs and PAHs from the atmosphere to the continental shelf sediments in the Koster Fjord, which is consistent with the hypothesis that the shelf sediments are important sinks for these compounds.     

Photochemical degradation of selected nitropolycyclic aromatic hydrocarbons in solution and adsorbed to solid particles

To examine the relationship between the nitro group orientation and photochemical degradation, a series of NPAHs, including 6-nitrochrysene, 9-nitroanthracene and 6-nitrobenzo(a)pyrene were irradiated both dissolved in CH3CN and adsorbed onto a surface (alumina, silica, carbon and cellulose). In solution, not all NPAHs displayed a relationship between their relative and nitro group orientation. In the adsorbed state, the nature of the particle appeared to have more of an influence than did the structure of the NPAH. If the compound degraded, the main product was generally a quinone.