A multi-cell, multi-scale model of vertebrate segmentation and somite formation

Somitogenesis, the formation of the body's primary segmental structure common to all vertebrate development, requires coordination between biological mechanisms at several scales. Explaining how these mechanisms interact across scales and how events are coordinated in space and time is necessary for a complete understanding of somitogenesis and its evolutionary flexibility. So far, mechanisms of somitogenesis have been studied independently. To test the consistency, integrability and combined explanatory power of current prevailing hypotheses, we built an integrated clock-and-wavefront model including submodels of the intracellular segmentation clock, intercellular segmentation-clock coupling via Delta/Notch signaling, an FGF8 determination front, delayed differentiation, clock-wavefront readout, and differential-cell-cell-adhesion-driven cell sorting. We identify inconsistencies between existing submodels and gaps in the current understanding of somitogenesis mechanisms, and propose novel submodels and extensions of existing submodels where necessary. For reasonable initial conditions, 2D simulations of our model robustly generate spatially and temporally regular somites, realistic dynamic morphologies and spontaneous emergence of anterior-traveling stripes of Lfng. We show that these traveling stripes are pseudo-waves rather than true propagating waves. Our model is flexible enough to generate interspecies-like variation in somite size in response to changes in the PSM growth rate and segmentation-clock period, and in the number and width of Lfng stripes in response to changes in the PSM growth rate, segmentation-clock period and PSM length.     

Effectiveness of the Antenatal Psychosocial Health Assessment (ALPHA) form in detecting psychosocial concerns: a randomized controlled trial

BackgroundA pregnant woman''s psychological health is a significant predictor of postpartum outcomes. The Antenatal Psychosocial Health Assessment (ALPHA) form incorporates 15 risk factors associated with poor postpartum outcomes of woman abuse, child abuse, postpartum depression and couple dysfunction. We sought to determine whether health care providers using the ALPHA form detected more antenatal psychosocial concerns among pregnant women than providers practising usual prenatal care.MethodsA randomized controlled trial was conducted in 4 communities in Ontario. Family physicians, obstetricians and midwives who see at least 10 prenatal patients a year enrolled 5 eligible women each. Providers in the intervention group attended an educational workshop on using the ALPHA form and completed the form with enrolled women. The control group provided usual care. After the women delivered, both groups of providers identified concerns related to the 15 risk factors on the ALPHA form for each patient and rated the level of concern. The primary outcome was the number of psychosocial concerns identified. Results were controlled for clustering.ResultsThere were 21 (44%) providers randomly assigned to the ALPHA group and 27 (56%) to the control group. A total of 227 patients participated: 98 (43%) in the ALPHA group and 129 (57%) in the control group. ALPHA group providers were more likely than control group providers to identify psychosocial concerns (odds ratio [OR] 1.8, 95% confidence interval [CI] 1.1–3.0; p = 0.02) and to rate the level of concern as “high” (OR 4.8, 95% CI 1.1–20.2; p = 0.03). ALPHA group providers were also more likely to detect concerns related to family violence (OR 4.8, 95% CI 1.9–12.3; p = 0.001).InterpretationUsing the ALPHA form helped health care providers detect more psychosocial risk factors for poor postpartum outcomes, especially those related to family violence. It is a useful prenatal tool, identifying women who would benefit from additional support and interventions.The psychosocial health of a pregnant woman and her family is a significant predictor of intrapartum, newborn and postpartum outcomes.^1,2,3,4 A critical review of the literature has identified an association between antenatal psychosocial risk factors and the poor postpartum outcomes of woman abuse, child abuse, postpartum depression and couple dysfunction.⁵Clinicians have indicated that a practical tool to help them systematically collect and record prenatal psychosocial information would be helpful.⁶Although specific and often well-validated tools are available to predict or detect child abuse, woman abuse or depression,^7,8,9,10 clinicians are unlikely to use them because of time constraints.¹ Other forms aid in collecting more comprehensive antenatal psychosocial data,^11,12,13,14 but they are not evidence-based, and were developed to predict obstetric or newborn rather than psychosocial outcomes.In contrast, the Antenatal Psychosocial Health Assessment (ALPHA) form (Appendix 1) was designed to identify antenatal psychosocial risk factors for poor postnatal psychosocial outcomes. It incorporates 15 risk factors found through critical literature review⁵ to be associated with woman abuse, child abuse, postpartum depression and couple dysfunction.¹⁵ These risk factors are grouped intuitively by topic, with suggested questions, into 4 categories: family factors, maternal factors, substance use and family violence. The ALPHA form has been field-tested by obstetricians, family physicians, midwives and nurses,^15,16 who have found using it to be feasible and useful.¹⁵ Pregnant women appreciate and feel comfortable with the psychosocial enquiry.¹⁵ The ALPHA form was developed as a screening tool to help providers systematically identify areas of psychosocial concern. Once feasibility was established,¹⁵ the next step was to determine whether using it in regular practice would increase the number of concerns identified.We sought to determine whether health care providers using the ALPHA form detected more antenatal psychosocial concerns in their pregnant patients than clinicians practising usual prenatal care. A secondary objective was to determine women''s and providers'' satisfaction with the ALPHA form.     

Resource-allocation rules and the heritability of traits

I hypothesize that the heritability of a trait, and thus its evolutionary responsiveness to natural selection, should be positively related to the priority with which resources are allocated to that trait. Low-priority traits are more sensitive to environmental effects, thus reducing the relative effect of genetic differences on phenotypic variation of these traits. This allocation-priority hypothesis explains why life-history traits, such as those involving growth and reproduction, generally have lower heritabilities than higher-priority morphological and physiological traits related to body maintenance. This hypothesis also shows how an organism-centered approach, as used in physiological ecology, can contribute to the development of evolutionary theory.     

Macroinvertebrate assemblages in Pennsylvania (U.S.A.) springs

Five distinct macroinvertebrate assemblages were identified using cluster analysis of the rank-order abundances of 13 orders in 15 freshwater springs of central Pennsylvania, U.S.A. A principal components analysis of 20 environmental factors indicated that an insect-dominated assemblage occurred in low pH, softwater sandstone springs and an amphipod-dominated assemblage was associated with medium to hardwater springs with a silt to gravel substratum. Three other assemblages were found in hardwater limestone springs: the peracaridan-hydrobiid assemblage was characterized by dense macrophyte beds and a silt to cobble substratum, the peracaridan-triclad-glossosomatid assemblage by a rubbly, gravel-cobble substratum and relatively high discharge, and the peracaridan-hydrobiid-oligochaete assemblage by a silty substratum and dense mats of green algae.Most of the common macroinvertebrate species were associated with specific physical, chemical, and (or) vegetational factors, but abundance associations between species pairs were generally lacking. We infer that assemblages are primarily determined by the match between the environmental mosaic of individual springs and the ecological requirements of the available species, rather than by strong interspecific interactions.Species-environment associations were assessed in an additional study of five closely neighboring springs in which some environmental variables of the wider study were nearly constant.     

Explorations in Anthropology and Theology

Explorations in Anthropology and Theology. Frank A. Salamone and Walter Randolph Adams. eds. Lanham, MD: University Press of America, 1997. 279 pp.     

The role of site-specific N-glycosylation in secretion of soluble forms of rabies virus glycoprotein

Rabies virus glycoprotein is important in the biology and pathogenesis of neurotropic rabies virus infection. This transmembrane glycoprotein is the only viral protein on the surface of virus particles, is the viral attachment protein that facilitates virus uptake by the infected cell, and is the target of the host humoral immune response to infection. The extracellular domain of this glycoprotein has N- glycosylation sequons at Asn37, Asn247, and Asn319. Appropriate glycosylation of these sequons is important in the expression of the glycoprotein. Soluble forms of rabies virus glycoprotein were constructed by insertion of a stop codon just external to the transmembrane domain. Using site-directed mutagenesis and expression in transfected eukaryotic cells, it was possible to compare the effects of site-specific glycosylation on the cell-surface expression and secretion of transmembrane and soluble forms, respectively, of the same glycoprotein. These studies yielded the surprising finding that although any of the three sequons permitted cell surface expression of full-length rabies virus glycoprotein, only the N-glycan at Asn319 permitted secretion of soluble rabies virus glycoprotein. Despite its biological and medical importance, it has not yet been possible to determine the crystal structure of the full-length transmembrane form of rabies virus glycoprotein which contains heterogeneous oligosaccharides. The current studies demonstrate that a soluble form of rabies virus glycoprotein containing only one sequon at Asn319 is efficiently secreted in the presence of the N-glycan processing inhibitor 1-deoxymannojirimycin. Thus, it is possible to purify a conformationally relevant form of rabies virus glycoprotein that contains only one N-glycan with a substantial reduction in its microheterogeneity. This form of the glycoprotein may be particularly useful for future studies aimed at elucidating the three-dimensional structure of this important glycoprotein.      

Psychological outcomes following maternal serum screening: a cohort study

BACKGROUND: Maternal serum screening is used to assist in the prenatal detection of congenital anomalies. Its use is controversial, and one concern that has been expressed is its psychological effects on women. The authors examined whether this test leads to an increase in anxiety and depression among women who have a false-positive result as compared with those who have a true-negative result or do not undergo testing. METHODS: A prospective cohort study with baseline assessment at 15 to 18 weeks'' gestation and follow-up at 24 weeks'' gestation was conducted. Pregnant women at 8 geographically diverse sites across Ontario were recruited. The main outcome measures were the state portion of the State--Trait Anxiety Inventory and the Center for Epidemiologic Studies Depression Scale. RESULTS: Of the 2418 potential subjects 2020 (83.5%) were enrolled and eligible; 1741 (86.2%) completed the follow-up. A total of 1177 women (67.6%) underwent maternal serum screening. No overall adverse psychological effects as a result of testing were found at 24 weeks'' gestation. Women with a false-positive result had a mean increase in anxiety score of 1.6 (95% confidence interval [CI] -1.7 to 4.9), whereas women with a true-negative result had a mean decrease of 1.1 (95% CI -1.8 to -0.3) and those not tested had a mean decrease of 0.4 (95% CI -1.3 to 0.5). The mean depression score increased by 0.5 (95% CI -0.9 to 2.0) in the false-positive group, was unchanged (95% CI -0.3 to 0.4) in the true-negative group and increased by 0.2 (95% CI -1.7 to 1.2) in the not tested group. Of the women who underwent testing, 87 (7.6%) were unsure of their result at the time of follow-up. INTERPRETATION: The results suggest that maternal screening in Ontario is not causing serious psychological harm to women. Communication regarding test results could be improved, since a substantial proportion of women were unsure of their test result.