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Tube Development (tube + development)
Selected AbstractsEtiology, pathogenesis and prevention of neural tube defectsCONGENITAL ANOMALIES, Issue 2 2006Rengasamy Padmanabhan ABSTRACT Spina bifida, anencephaly, and encephalocele are commonly grouped together and termed neural tube defects (NTD). Failure of closure of the neural tube during development results in anencephaly or spina bifida aperta but encephaloceles are possibly post-closure defects. NTD are associated with a number of other central nervous system (CNS) and non-neural malformations. Racial, geographic and seasonal variations seem to affect their incidence. Etiology of NTD is unknown. Most of the non-syndromic NTD are of multifactorial origin. Recent in vitro and in vivo studies have highlighted the molecular mechanisms of neurulation in vertebrates but the morphologic development of human neural tube is poorly understood. A multisite closure theory, extrapolated directly from mouse experiments highlighted the clinical relevance of closure mechanisms to human NTD. Animal models, such as circle tail, curly tail, loop tail, shrm and numerous knockouts provide some insight into the mechanisms of NTD. Also available in the literature are a plethora of chemically induced preclosure and a few post-closure models of NTD, which highlight the fact that CNS malformations are of hetergeneitic nature. No Mendelian pattern of inheritance has been reported. Association with single gene defects, enhanced recurrence risk among siblings, and a higher frequency in twins than in singletons indicate the presence of a strong genetic contribution to the etiology of NTD. Non-availability of families with a significant number of NTD cases makes research into genetic causation of NTD difficult. Case reports and epidemiologic studies have implicated a number of chemicals, widely differing therapeutic drugs, environmental contaminants, pollutants, infectious agents, and solvents. Maternal hyperthermia, use of valproate by epileptic women during pregnancy, deficiency and excess of certain nutrients and chronic maternal diseases (e.g. diabetes mellitus) are reported to cause a manifold increase in the incidence of NTD. A host of suspected teratogens are also available in the literature. The UK and Hungarian studies showed that periconceptional supplementation of women with folate (FA) reduces significantly both the first occurrence and recurrence of NTD in the offspring. This led to mandatory periconceptional FA supplementation in a number of countries. Encouraged by the results of clinical studies, numerous laboratory investigations focused on the genes involved in the FA, vitamin B12 and homocysteine metabolism during neural tube development. As of today no clinical or experimental study has provided unequivocal evidence for a definitive role for any of these genes in the causation of NTD suggesting that a multitude of genes, growth factors and receptors interact in controlling neural tube development by yet unknown mechanisms. Future studies must address issues of gene-gene, gene-nutrient and gene,environment interactions in the pathogenesis of NTD. [source] Early differentiation and migration of cranial neural crest in the opossum, Monodelphis domesticaEVOLUTION AND DEVELOPMENT, Issue 2 2003Janet L. Vaglia SUMMARY Marsupial mammals are born at a highly altricial state. Nonetheless, the neonate must be capable of considerable functional independence. Comparative studies have shown that in marsupials the morphogenesis of many structures critical to independent function are advanced relative to overall development. Many skeletal and muscular elements in the facial region show particular heterochrony. Because neural crest cells are crucial to forming and patterning much of the face, this study investigates whether the timing of cranial neural crest differentiation is also advanced. Histology and scanning electron microscopy of Monodelphis domestica embryos show that many aspects of cranial neural crest differentiation and migration are conserved in marsupials. For example, as in other vertebrates, cranial neural crest differentiates at the neural ectoderm/epidermal boundary and migrates as three major streams. However, when compared with other vertebrates, a number of timing differences exist. The onset of cranial neural crest migration is early relative to both neural tube development and somite formation in Monodelphis. First arch neural crest cell migration is particularly advanced and begins before any somites appear or regional differentiation exists in the neural tube. Our study provides the first published description of cranial neural crest differentiation and migration in marsupials and offers insight into how shifts in early developmental processes can lead to morphological change. [source] Adhesion and development of the root rot fungus (Heterobasidion annosum) on conifer tissues: effects of spore and host surface constituentsFEMS MICROBIOLOGY ECOLOGY, Issue 2 2000Frederick O Asiegbu Abstract The objective of this study was to correlate the occurrence of particular root and woody stump surface components with the ability of spores of the root rot fungus (Heterobasidion annosum) to adhere, germinate and establish on conifer tissues. With the aid of high performance liquid chromatography, several sugars (pinitol, xylitol, dulcitol, mannitol, D -glucose, mannose, fructose) were detected on both stump and fine root surfaces of Scots pine and Norway spruce. Of all the sugars observed, xylose and arabinose were poorly utilized for initiation of germ tube growth whereas spore germination was enhanced in the presence of D -glucose, mannose or fructose. Oxidation of these sugars by pretreatment of wood discs or roots with periodic acid abolished the ability of the spores to germinate. Non-sugar components such as long chain fatty acids on spores and root surfaces as detected with nuclear magnetic resonance were found to have a significant influence on adhesion and initiation of germ tube development. Removal of these aliphatic compounds from the root surface increased spore germination by 2-fold, whereas similar treatment on spores led to a 5-fold decrease in adhesiveness to root material. In vitro studies revealed that the di-ethyl ether extract from the roots had no long term adverse effect on spore germination which suggests that the fungus may possess the capability to detoxify this substance. Similarly, adhesion of spores was affected by low and freezing temperatures. The role of significant levels of mannitol and trehalose accumulated in spores and hyphae of the fungi on viability, survival and tolerance to adverse conditions such as oxidative stress, freezing and desiccation are discussed. [source] Sfrp1, Sfrp2, and Sfrp5 regulate the Wnt/,-catenin and the planar cell polarity pathways during early trunk formation in mouseGENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 2 2008Wataru Satoh The secreted frizzled-related protein gene family encodes proteins that regulate Wnt signaling. Msx1 in situ hybridization of 9.5 days post coitus mouse embryos showing normal neural tube development in an Sfrp1; Sfrp2 double mutant (left) but severe neural tube defects in a Looptail (Lp/+); Sfrp1; Sfrp2 triple mutant (right). These findings suggest that Sfrps regulate the Wnt planar cell polarity pathway. See Satoh et al. in this issue. [source] Rapid Screening Method of Cassava Cultivars for Resistance to Colletotrichum gloeosporioides f.sp. manihotisJOURNAL OF PHYTOPATHOLOGY, Issue 1 2002C. N. FOKUNANG An in vitro method for assessing cassava anthracnose disease (CAD) resistance was developed as a preliminary screen to a CAD-resistant breeding programme. Potato dextrose agar (PDA) media was amended by extracts from the stem cortex of 10 cassava cultivars (30001; 30572, 30211, 88/02549, 88/00695, 88/01336, 91/00344, 91/00313, 91/00684 and 91/00475), and assayed for efficacy of inhibition of the growth of Colletotrichum gloeosporioides f. sp. manihotis isolates (05FCN, 10FCN, 12FCN, and 18FCN). Morphological and physiological data indicated that there was a significant difference (P , 0.05), in mycelial growth, spore germination and sporulation among the four isolates on PDA amended with cassava stem extracts. Extracts from cassava cultivars 30211, 91/00684 and 91/00313 showed higher inhibition of germ tube development, mycelial growth and sporulation of the fungal isolates, whereas cultivars 88/02549 and 88/01336 showed the least inhibition. The 10 cultivars were further tested in both greenhouse and field conditions, under disease pressure for two planting seasons, to corroborate resistance to the fungus as observed in vitro. Greenhouse and field trials with the 10 cassava cultivars showed a significant difference (P , 0.05) in CAD resistance. Cultivars 88/02549 and 88/01336 were highly CAD-susceptible, as shown in the in vitro assays and confirmed in the greenhouse and field tests. The other eight cultivars were either resistant (30211, 91/00684), or moderately resistant (30572, 88/00695, 91/00475, 91/00344, 30001 and 91/00313) to CAD. The study shows that an in vitro screening assay of cassava for resistance to CAD could serve as a convenient preliminary screening technique to discriminate CAD-resistant from CAD-susceptible cassava cultivars. The in vitro screening method considerably reduces time and labour in comparison with the current screening techniques of cassava, which involve field planting, inoculation and evaluation. [source] | ||||||||||