Invasive Crayfish Threaten the Development of Submerged Macrophytes in Lake Restoration

Submerged macrophytes enhance water transparency and aquatic biodiversity in shallow water ecosystems. Therefore, the return of submerged macrophytes is the target of many lake restoration projects. However, at present, north-western European aquatic ecosystems are increasingly invaded by omnivorous exotic crayfish. We hypothesize that invasive crayfish pose a novel constraint on the regeneration of submerged macrophytes in restored lakes and may jeopardize restoration efforts. We experimentally investigated whether the invasive crayfish (Procambarus clarkii Girard) affects submerged macrophyte development in a Dutch peat lake where these crayfish are expanding rapidly. Seemingly favourable abiotic conditions for macrophyte growth existed in two 0.5 ha lake enclosures, which provided shelter and reduced turbidity, and in one lake enclosure iron was added to reduce internal nutrient loading, but macrophytes did not emerge. We transplanted three submerged macrophyte species in a full factorial exclosure experiment, where we separated the effect of crayfish from large vertebrates using different mesh sizes combined with a caging treatment stocked with crayfish only. The three transplanted macrophytes grew rapidly when protected from grazing in both lake enclosures, demonstrating that abiotic conditions for growth were suitable. Crayfish strongly reduced biomass and survival of all three macrophyte species while waterfowl and fish had no additive effects. Gut contents showed that crayfish were mostly carnivorous, but also consumed macrophytes. We show that P. clarkii strongly inhibit macrophyte development once favourable abiotic conditions for macrophyte growth are restored. Therefore, expansion of invasive crayfish poses a novel threat to the restoration of shallow water bodies in north-western Europe. Prevention of introduction and spread of crayfish is urgent, as management of invasive crayfish populations is very difficult.     

Proliferation of Murine Midbrain Neural Stem Cells Depends upon an Endogenous Sonic Hedgehog (Shh) Source

The Sonic Hedgehog (Shh) pathway is responsible for critical patterning events early in development and for regulating the delicate balance between proliferation and differentiation in the developing and adult vertebrate brain. Currently, our knowledge of the potential role of Shh in regulating neural stem cells (NSC) is largely derived from analyses of the mammalian forebrain, but for dorsal midbrain development it is mostly unknown. For a detailed understanding of the role of Shh pathway for midbrain development in vivo, we took advantage of mouse embryos with cell autonomously activated Hedgehog (Hh) signaling in a conditional Patched 1 (Ptc1) mutant mouse model. This animal model shows an extensive embryonic tectal hypertrophy as a result of Hh pathway activation. In order to reveal the cellular and molecular origin of this in vivo phenotype, we established a novel culture system to evaluate neurospheres (nsps) viability, proliferation and differentiation. By recreating the three-dimensional (3-D) microenvironment we highlight the pivotal role of endogenous Shh in maintaining the stem cell potential of tectal radial glial cells (RGC) and progenitors by modulating their Ptc1 expression. We demonstrate that during late embryogenesis Shh enhances proliferation of NSC, whereas blockage of endogenous Shh signaling using cyclopamine, a potent Hh pathway inhibitor, produces the opposite effect. We propose that canonical Shh signaling plays a central role in the control of NSC behavior in the developing dorsal midbrain by acting as a niche factor by partially mediating the response of NSC to epidermal growth factor (EGF) and fibroblast growth factor (FGF) signaling. We conclude that endogenous Shh signaling is a critical mechanism regulating the proliferation of stem cell lineages in the embryonic dorsal tissue.     

Mortality from Congenital Heart Disease in Mexico: A Problem on the Rise

Background and Objectives

Temporal trends in mortality from congenital heart disease (CHD) vary among regions. It is therefore necessary to study this problem in each country. In Mexico, congenital anomalies were responsible for 24% of infant mortality in 2013 and CHD represented 55% of total deaths from congenital anomalies among children under 1 year of age. The objectives of this study were to analyze the trends in infant mortality from CHD in Mexico (1998 to 2013), its specific causes, age at death and associated socio-demographic factors.

Methods

Population-based study which calculated the compounded annual growth rate of death rom CHD between 1998 and 2013. Specific causes, age at which death from CHD occurred and risk factors associated with mortality were analyzed for the year 2013.

Results

Infant mortality from CHD increased 24.8% from 1998 to 2013 (114.4 to 146.4/ 100,000 live births). A total of 3,593 CHD deaths occurred in 2013; the main causes were CHD with left-to-right shunt (n = 487; 19.8/100,000 live births) and cyanotic heart disease (n = 410; 16.7/100,000). A total of 1,049 (29.2%) deaths from CHD occurred during the first week of life. Risk factors associated with mortality from CHD were, in order of magnitude: non-institutional birth, rural area, birth in a public hospital and male sex.

Conclusions

Mortality from CHD has increased in Mexico. The main causes were CHD with left-to-right shunt, which are not necessarily fatal if treated promptly. Populations vulnerable to death from CHD were identified. Approximately one-third of the CHD occurred during the first week of life. It is important to promote early diagnosis, especially for non-institutional births.     

Patterns of population structure at microsatellite and mitochondrial DNA markers in the franciscana dolphin (Pontoporia blainvillei)

The franciscana dolphin, Pontorporia blainvillei, is an endemic cetacean of the Atlantic coast of South America. Its coastal distribution and restricted movement patterns make this species vulnerable to anthropogenic factors, particularly to incidental bycatch. We used mitochondrial DNA control region sequences, 10 microsatellites, and sex data to investigate the population structure of the franciscana dolphin from a previously established management area, which includes the southern edge of its geographic range. F‐statistics and Bayesian cluster analyses revealed the existence of three genetically distinct populations. Based on the microsatellite loci, similar levels of genetic variability were found in the area; 13 private alleles were found in Monte Hermoso, but none in Claromecó. When considering the mitochondrial DNA control region sequences, lower levels of genetic diversity were found in Monte Hermoso, when compared to the other localities. Low levels of gene flow were found between most localities. Additionally, no evidence of isolation by distance nor sex‐biased dispersal was detected in the study area. In view of these results showing that populations from Necochea/Claromecó, Monte Hermoso, and Río Negro were found to be genetically distinct and the available genetic information for the species previously published, Argentina would comprise five distinct populations: Samborombón West/Samborombón South, Cabo San Antonio/Buenos Aires East, Necochea/Claromecó/Buenos Aires Southwest, Monte Hermoso, and Río Negro. In order to ensure the long‐term survival of the franciscana dolphin, management and conservation strategies should be developed considering each of these populations as different management units.     

Mitochondrial implications in human pregnancies with intrauterine growth restriction and associated cardiac remodelling

Intrauterine growth restriction (IUGR) is an obstetric complication characterised by placental insufficiency and secondary cardiovascular remodelling that can lead to cardiomyopathy in adulthood. Despite its aetiology and potential therapeutics are poorly understood, bioenergetic deficits have been demonstrated in adverse foetal and cardiac development. We aimed to evaluate the role of mitochondria in human pregnancies with IUGR. In a single‐site, cross‐sectional and observational study, we included placenta and maternal peripheral and neonatal cord blood mononuclear cells (PBMC and CBMC) from 14 IUGR and 22 control pregnancies. The following mitochondrial measurements were assessed: enzymatic activities of mitochondrial respiratory chain (MRC) complexes I, II, IV, I + III and II + III, oxygen consumption (cell and complex I‐stimulated respiration), mitochondrial content (citrate synthase [CS] activity and mitochondrial DNA copy number), total ATP levels and lipid peroxidation. Sirtuin3 expression was evaluated as a potential regulator of bioenergetic imbalance. Intrauterine growth restriction placental tissue showed a significant decrease of MRC CI enzymatic activity (P < 0.05) and CI‐stimulated oxygen consumption (P < 0.05) accompanied by a significant increase of Sirtuin3/β‐actin protein levels (P < 0.05). Maternal PBMC and neonatal CBMC from IUGR patients presented a not significant decrease in oxygen consumption (cell and CI‐stimulated respiration) and MRC enzymatic activities (CII and CIV). Moreover, CS activity was significantly reduced in IUGR new‐borns (P < 0.05). Total ATP levels and lipid peroxidation were preserved in all the studied tissues. Altered mitochondrial function of IUGR is especially present at placental and neonatal level, conveying potential targets to modulate obstetric outcome through dietary interventions aimed to regulate Sirtuin3 function.     

Effects of temperature and water availability on light energy utilization in photosynthetic processes of Deschampsia antarctica

Regional climate change in Antarctica would favor the carbon assimilation of Antarctic vascular plants, since rising temperatures are approaching their photosynthetic optimum (10–19°C). This could be detrimental for photoprotection mechanisms, mainly those associated with thermal dissipation, making plants more susceptible to eventual drought predicted by climate change models. With the purpose to study the effect of temperature and water availability on light energy utilization and putative adjustments in photoprotective mechanisms of Deschampsia antarctica Desv., plants were collected from two Antarctic provenances: King George Island and Lagotellerie Island. Plants were cultivated at 5, 10 and 16°C under well‐watered (WW) and water‐deficit (WD, at 35% of the field capacity) conditions. Chlorophyll fluorescence, pigment content and de‐epoxidation state were evaluated. Regardless of provenances, D. antarctica showed similar morphological, biochemical and functional responses to growth temperature. Higher temperature triggered an increase in photochemical activity (i.e. electron transport rate and photochemical quenching), and a decrease in thermal dissipation capacity (i.e. lower xanthophyll pool, Chl a/b and β carotene/neoxanthin ratios). Leaf mass per unit area was reduced at higher temperature, and was only affected in plants exposed to WD at 16°C and exhibiting lower electron transport rate and amount of chlorophylls. D. antarctica is adapted to frequent freezing events, which may induce a form of physiological water stress. Photoprotective responses observed under WD contribute to maintain a stable photochemical activity. Thus, it is possible that short‐term temperature increases could favor the photochemical activity of this species. However, long‐term effects will depend on the magnitude of changes and the plant's ability to adjust to new growth temperature.     

Age at acquisition of Helicobacter pylori infection: comparison of two areas with contrasting risk of gastric cancer

Background. Helicobacter pylori infection is usually acquired during childhood and is a known risk factor for the development of gastric malignancies in adulthood. It has been reported that early age at first infection may determine a neoplastic outcome in adults. The purpose of this study was to determine the prevalence of Helicobacter pylori infection in children residing in areas with high (Pasto) and low risk (Tumaco) of gastric cancer in Colombia to evaluate whether differences in the age of acquisition of H. pylori infection were present in the two populations. Materials and Methods. The study sample was based on a census taken in 1999. Using the ¹³C‐urea breath test, we compared the prevalence of H. pylori infection among children aged 1–6 years. Results. Among 345 children in Pasto, 206 (59.7%) were H. pylori‐positive, compared with 188 (58.6%) among 321 children in Tumaco. The two populations share a common pattern of very early age at infection and marked increase in prevalence during the first 4 years of life. No differences in any one year were observed when comparing the two groups. Conclusions. The prevalence of infection was similarly high and increased with age in both populations. In these populations the age of acquisition of H. pylori after 1 year of age does not appear to be a primary factor responsible for the differences in the rates of gastric cancer incidence in adults. Previous findings in adults showed lower prevalence of the most virulent genotypes in Tumaco compared to Pasto, and bacterial virulence may play a key role in determining cancer outcome.