Type of disturbance and ecological history determine structural stability.

This study aims to reveal whether complexity, namely, community and trophic structure, of chronically stressed soil systems is at increased risk or remains stable when confronted with a subsequent disturbance. Therefore, we focused on a grassland with a history of four centuries of patchy contamination. Nematodes were used as model organisms because they are an abundant and trophically diverse group and representative of the soil food web and ecosystem complexity. In a field survey, a relationship between contaminants and community structures was established. Following, two groups of soil mesocosms from the field that differed in contamination level were exposed to different disturbance regimes, namely, to the contaminant zinc and a heat shock. The zinc treatment revealed that community structure is stable, irrespective of soil contamination levels. This implies that centuries of exposure to contamination led to adaptation of the soil nematode community irrespective of the patchy distribution of contaminants. In contrast, the heat shock had adverse effects on species richness in the highly contaminated soils only. The total nematode biomass was lower in the highly contaminated field samples; however, the biomass was not affected by zinc and heat treatments of the mesocosms. This means that density compensation occurred rapidly, i.e., tolerant species quickly replaced sensitive species. Our results support the hypothesis that the history of contamination and the type of disturbance determine the response of communities. Despite that ecosystems may be exposed for centuries to contamination and communities show adaptation, biodiversity in highly contaminated sites is at increased risk when exposed to a different disturbance regime. We discuss how the loss of higher trophic levels from the entire system, such as represented by carnivorous nematodes after the heat shock, accompanied by local biodiversity loss at highly contaminated sites, may result in detrimental effects on ecosystem functions.     

Interactions of 2,2′,4,4′,5,5′-hexachlorobiphenyl and 2,3,7,8-tetrachlorodibenzo-p-dioxin in a subchronic feeding study in the rat

Female (SD) rats were fed diets containing 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) in various concentrations for three months. PCB 153 had no significant effect on the body weight gain when given alone or in combination with TCDD. The increases in relative liver weights were additive. For thymic atrophy no interactive effects became apparent. PCB 153 had no effect on the EROD induction by TCDD. PROD induction by PCB 153 was diminished in the presence of TCDD. The level of TCDD in the liver was decreased by PCB 153. Increasing TCDD dosage led to an increase in PCB 153 levels.     

Soil organic matter from pioneer species and its implications to phytostabilization of mined sites in the Sierra de Cartagena (Spain)

Pioneer plant species were observed growing on mined areas despite unfavourable conditions such as extreme pH, high salinity and phytotoxic levels of several elements. This study evaluated the contribution of pioneer species to the accumulation of soil organic matter (SOM). We collected 51 samples from 17 non-vegetated, natural and pioneer-vegetated sites in five highly saline mined areas in the Sierra de Cartagena (Spain). The composition of SOM was determined using total C, N and S elemental anlayzer, pyrolysis and solid state (13)C NMR spectroscopy. Results showed that pioneer species like Lygeum spartum had contributed approximately 11 kg SOM kg(-1) soil into the Balsa Rosa sites since 1991; it will take approximately 120 years of continuous growth for this plant to increase the SOM level comparable to natural site. In the Portman Bay area, Sarconia ramosissima and Phragmites australis can contribute SOM equivalent to present day SOM in natural sites in the next 30 years. Low quality SOM (C/N>20) deposited by pioneer plants was dominated by lignin-derived organic compounds such as phenols, guaiacols, syringols and aromatics while polyssacharides and alkyls were the major components in high quality SOM (C/N<20). The addition of SOM to mine wastes is similar to early stages of soil formation and with time, we expect the formation of well-developed Ah horizon on the surface of mine wastes. The presence of P. australis on several sites makes it a very good candidate for successful revegetation of hostile conditions found in many mined sites.     

Identifying key issues in environmental wetland research using scaling and uncertainty analysis

Quantification of the response of wetlands to environmental change and of climate change to wetland processes, is a pressing, but complex, issue. Findings of widely diverse investigations have to be generalised to identify the key issues and the gaps in knowledge. Two tools for generalisation, scaling and uncertainty analysis, were applied here to two case studies and act as stepping stones for analysis of key issues. The first case study is on methane emissions from wetland rice fields and the second is on the restoration of wet dune slacks. The type of problems encountered depends on the scale at which a process is studied. At the biogeochemical processes scale, knowledge on some key parameters, but especially on interactions between key parameters is limiting. At the vegetation scale, feedbacks between processes become especially important, whereas at even larger scales increasingly stringent approximations of interactions have to be made. Accumulating uncertainties at the landscape scale need careful evaluation. Apart from uncertainties in the approximations and their interactions, those introduced by spatial and temporal variability as well as by different data sources highly influence the accuracy of response estimates, while these last sources of uncertainty are neglected in many studies. Only by explicitly accounting for scaling effects and their resulting uncertainties, the interactions between wetlands and environment can be understood.     

Two unbalanced segregation products due to a maternal t(7;16)inv(16)

We report a prenatal case of a maternally inherited abnormal chromosome 16, originally interpreted as a pericentric inversion only, but after family studies re-interpreted as a pericentric inversion (16) accompanied by an unbalanced (7;16) translocation. Because of the inversion 16 and an elder son with developmental delay and craniofacial dysmorphic features, in the past karyotyped as 46,XY, the chromosomes 16 of the mother and son were carefully re-examined. Using a whole chromosome 16 paint and sub-telomere probes of 16p and 16q, the karyotype of the mother was shown to be 46,XX,inv(16)(p11.2q23.2).ish t(7;16)(q36;p13.3)inv(16). Subsequently one chromosome 16 of the elder son appeared to be a der(16)t(7;16)(q36;p13.3). This is probably the result of a meiotic crossover between the chromosomes 16 in the mother. The prenatal karyotype was finally interpreted as 46,XY,inv(16)(p11.2q23.2).ish der(16)t(7;16)(q36;p13.3)inv(16). This is the same cytogenetic imbalance as his elder brother: a partial trisomy of chromosome 7 (q36→qter) and a partial monosomy of chromosome 16 (p13.3→pter). Copyright © 2001 John Wiley & Sons, Ltd.     

Development of a simulator for training of fetoscopic myelomeningocele surgery

Objective

To develop a realistic simulation model for laparotomy-assisted fetoscopic spina bifida aperta (SBa) surgery, to be used for training purposes and preoperative planning.

Methods

The predefined general requirement was a realistic model of an exteriorized uterus, allowing all neurosurgical steps of the intervention. The uterus was modelled using ultrasound and MRI images of a 25 weeks’ gravid uterus, consisting of flexible polyurethane foam coated with pigmented silicone. The fetal model, contained an opening on the dorsal side for a customizable spinal insert with all the aspects of a SBa, including a cele, placode, and myofascial and skin layer. The model was assessed in a series of validation experiments.

Results

Production costs are low, uterus and fetus are reusable. Placental localization and the level and size of the spinal defect are adjustable, enabling case-specific adaptations. All aspects of the simulator were scored close to realistic or higher for both appearance and functional capacities.

Conclusions

This innovative model provides an excellent training opportunity for centers that are starting a fetoscopic SBa repair program. It is the first simulation model with adjustable spinal defect and placental localisation. Further objective validation is required, but the potential for using this model in preoperative planning is promising.     

Congenital small bowel obstruction: Prenatal detection and outcome

Objective

To evaluate and compare the outcome of fetuses and neonates with congenital small bowel obstructions (SBO), evaluate the screening performance of prenatal ultrasound for SBO and identify possible risk factors for adverse outcomes.

Methods

All cases referred to the Amsterdam University Medical Centers between 2007 and 2021 for a prenatal suspected SBO, supplemented by cases of postnatal diagnosis of SBO, were included. The primary outcome was survival after 24 weeks of gestation until the first year of life.

Results

147 cases of SBO were included with a survival rate of 86.2% (119/138) after 24 weeks of gestation until the first year of age. Additional structural or chromosomal anomalies were found to have an increased risk of adverse outcomes. Intrauterine fetal demise occurred in 10/147 (6.8%) cases and 9/147 (6.1%) cases died during postnatal follow-up. The overall positive predictive value of all prenatally diagnosed cases was 91.5%. Surgical correction was performed in 123/128 (96.0%) of the live-born cases.

Conclusions

Congenital SBO has an overall favorable prognosis, but the outcome is negatively impacted by the possible presence of additional structural or chromosomal anomalies. Fetal monitoring in the early third trimester should be considered, since all cases of Intrauterine fetal demise occurred between 30 and 35 weeks of gestation.