Gene expression and digit homology in the chicken embryo wing

The bird wing is of special interest to students of homology and avian evolution. Fossil and developmental data give conflicting indications of digit homology if a pentadactyl "archetype" is assumed. Morphological signs of a vestigial digit I are seen in bird embryos, but no digit-like structure develops in wild-type embryos. To examine the developmental mechanisms of digit loss, we studied the expression of the high-mobility group box containing Sox9 gene, and bone morphogenetic protein receptor 1b (bmpR-1b)-markers for precondensation and prechondrogenic cells, respectively. We find an elongated domain of Sox9 expression, but no bmpR-1b expression, anterior to digit II. We interpret this as a digit I domain that reaches precondensation, but not condensation or precartilage stages. It develops late, when the tissue in which it is lodged is being remodeled. We consider these findings in the light of previous Hoxd-11 misexpression studies. Together, they suggest that there is a digit I vestige in the wing that can be rescued and undergo development if posterior patterning cues are enhanced. We observed Sox9 expression in the elusive "element X" that is sometimes stated to represent a sixth digit. Indeed, incongruity between digit domains and identities in theropods disappears if birds and other archosaurs are considered primitively polydactyl. Our study provides the first gene expression evidence for at least five digital domains in the chick wing. The failure of the first to develop may be plausibly linked to attenuation of posterior signals.     

Can folic acid protect against congenital heart defects in down syndrome?

BACKGROUND: Several studies have suggested a protective effect of folic acid (FA) on congenital heart anomalies. Down syndrome (DS) infants are known to have a high frequency of heart anomalies. Not all children with DS suffer from heart anomalies, which raises the question whether maternal factors might affect the risk of these anomalies. Our objectives were to investigate whether first-trimester FA use protects against heart anomalies among DS children. METHODS: Women with liveborn DS children participating in the Slone Epidemiology Center Birth Defects Study between 1976 and 1997 were included. We performed case-control analyses using DS, with heart anomalies as cases and DS, without heart anomalies as controls. Subanalyses were performed for defects that have been associated with FA in non-DS populations (conotruncal, ventricular septal [VSD]) and for those that are associated with DS (ostium secundum type atrial septal defects [ASD] and endocardial cushion defects [ECD]). Exposure was defined as the use of any FA-containing product for an average of at least 4 days per week during the first 12 weeks of pregnancy, whereas no exposure was defined as no use of FA in these 12 weeks. RESULTS: Of the 223 cases, 110 (49%) were exposed versus 84 (46%) of the 184 controls. After adjustment for possible confounders, no protective effect of FA was found on heart anomalies overall (OR 0.95, 95% CI: 0.61-1.47) nor separately for conotruncal defects, VSDs, ASDs, or ECDs. CONCLUSIONS: Our study does not show a protective effect of FA on heart anomalies among infants with DS.     

Prevalence of genital HPV infections and HPV serology in adolescent girls,prior to vaccination

Introduction: Monitoring the prevalence of type-specific HPV-DNA infections before and shortly after introduction of routine HPV vaccination offers the opportunity to evaluate early effects of the vaccination program. With this aim a cohort study was set up of 14- to 16-year-old girls eligible for HPV vaccination in the Netherlands. Annually, HPV-DNA and antibody status in vaginal self-samples and in serum respectively, will be studied among vaccinated (58%) and unvaccinated girls (42%). Here we present baseline data on vaginal HPV-DNA status in relation to serum antibodies. Methods: The 1800 enrolled girls filled out an internet-based questionnaire and provided a vaginal self-sample for genotype specific HPV-DNA detection using SPF₁₀ PCR amplification and reverse line probe hybridization. Furthermore, 64% of the girls provided a blood sample for HPV antibody analysis. IgG antibodies against virus-like particles were determined for 7 HPV genotypes. Results: At baseline, type-specific HPV-DNA was detected in 4.4% (n = 79) of the 1800 girls: 2.7% (n = 49) concerned a high risk HPV type (hrHPV-DNA). The three most common types were HPV type 16, 18 and 51 (40%). Out of the hrHPV-DNA positive girls, 32% was seropositive vs. 12% in HPV-DNA negative girls (p < 0.001). Risk factors independently associated with hrHPV-DNA infection among the sexually active girls were age >15 years vs. 14–15 years (OR = 2.6 (1.2–5.9)), age of sexual debut <14 vs. above 14 years (OR = 3.0 (1.1–8.2)), total number of lifetime partners above two vs. less than two partners (OR = 3.2 (1.3–8.0)) and age of partner >17 vs. under 17 years (OR = 4.2 (1.5–13.0)). Conclusion: A low hrHPV-DNA prevalence was found in the adolescent girls. The observed vs. expected age-related increase in HPV-DNA prevalence in this cohort in the coming years (with increased sexual activity) will provide understanding of the effect of HPV vaccination. Furthermore, this cohort study will offer the opportunity to improve knowledge of antibody responses following natural infection and vaccination.     

Fractal Patterns of Neural Activity Exist within the Suprachiasmatic Nucleus and Require Extrinsic Network Interactions

The mammalian central circadian pacemaker (the suprachiasmatic nucleus, SCN) contains thousands of neurons that are coupled through a complex network of interactions. In addition to the established role of the SCN in generating rhythms of ∼24 hours in many physiological functions, the SCN was recently shown to be necessary for normal self-similar/fractal organization of motor activity and heart rate over a wide range of time scales—from minutes to 24 hours. To test whether the neural network within the SCN is sufficient to generate such fractal patterns, we studied multi-unit neural activity of in vivo and in vitro SCNs in rodents. In vivo SCN-neural activity exhibited fractal patterns that are virtually identical in mice and rats and are similar to those in motor activity at time scales from minutes up to 10 hours. In addition, these patterns remained unchanged when the main afferent signal to the SCN, namely light, was removed. However, the fractal patterns of SCN-neural activity are not autonomous within the SCN as these patterns completely broke down in the isolated in vitro SCN despite persistence of circadian rhythmicity. Thus, SCN-neural activity is fractal in the intact organism and these fractal patterns require network interactions between the SCN and extra-SCN nodes. Such a fractal control network could underlie the fractal regulation observed in many physiological functions that involve the SCN, including motor control and heart rate regulation.     

Carbon metabolism of Frankia spp. in root nodules of Alnus glutinosa and Hippophaë rhamnoides

The occurrence and localization of enzymes involved in glycolysis, tricarboxylic acid cycle and glyoxylate cycle in root nodules of Alnus glutinosa (L.) Vill. and Hippophaë rhamnoides L. ssp. rhamnoides were studied. The following enzymes, catalyzing reversible steps in the glycolysis, were found in both the endophyte Frankia spp. and the plant cytosol of Alnus nodules: fructose-1,6-diphosphate aldolase, glyceralde-hyde-3-phosphate dehydrogenase, phosphoglycerate kinase and enolase. The enzymes catalyzing irreversible steps in glycolysis, viz. hexokinase and pyruvate kinase, were detectable only in the plant cytosol. Similar results were obtained with nodule homogenates of Hippophaë. This indicates the absence of a complete glycolysis in the endophyte. Vesicle clusters of the nodule endophyte of Alnus contained various dehydrogenases of the tricarboxylic acid cycle and showed activity of glutamate oxaloacetate transaminase. Respiration studies showed that vesicle clusters take up oxygen when supplied with NAD, glutamate and malate together. No oxygen uptake was found when any of these compounds was omitted. Vesicle clusters from both Alnus and Hippophaë nodules showed no detectable activity of the glyoxylate cycle enzymes isocitrate lyase and malate synthase. Since these enzymes are known to be present in Frankia Avcll, when grown in a medium with Tween 80 as carbon source, it is suggested that the glyoxylate cycle enzymes are repressed in the root-nodule symbioses.