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Topic: Segmentation (biology)

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	Segmentation - Wikipedia, the free encyclopedia
		Segmentation is a general term for the division or partition of something into separate pieces or segments.
		segmentation (biology), the structure that results from said process.
		Segmentation (memory), the division of main memory into memory subsystems.
	en.wikipedia.org /wiki/Segmentation (210 words)

	Segmentation (biology) - Wikipedia, the free encyclopedia
		Segmentation in biology refers to the division of some metazoan bodies and plant body plans into a series of semi-repetitive segments, and the question of the benefits and costs of doing so.
		Vertebrate vertebrae are also inherited in a segmented way, making it easy for those animals to adapt to have the correct number of these in their vertebral column.
		Among the plants, the horsetails are a clear example of segmentation.
	en.wikipedia.org /wiki/Segmentation_(biology) (141 words)

	Santiago Schnell's Research Interests
		Segmentation is a basic characteristic of many animal species including man, and usually corresponds to a repetition, along the anterior-posterior axis, of similar structures during early development.
		Functionally, segmentation is critical to ensure the movements of a rod-like structure, such as the vertebral column.
		The segmented distribution of the vertebrae derives from the earlier metameric pattern of embryonic structures known as somites.
	www.informatics.indiana.edu /schnell/research/embryology.asp (716 words)

	Earthworm Biology (Site not responding. Last check: 2007-10-26)
		The most noticeable external feature (Figure 3) is the ringing or segmentation of the body, which is not merely external but involves nearly all of the internal structure.
		Segmentation within the earthworm serves the same general function as the division of the animal body into organs--that is, different segments perform different functions.
		The first section of the earthworm, the anterior end or head, consists of the mouth and the prostomium, a lobe which serves as a covering for the mouth and as a wedge to force open cracks in the soil into which the earthworm may crawl.
	edis.ifas.ufl.edu /IN047 (1198 words)

	Elaine Seaver - Department of Zoology, University of Hawaii
		Segmented animals are found within 3 major clades: the chordates, arthropods and annelids.
		The annelids are the least understood at the molecular level of how they generate segments during development, and we are trying to understand the cellular and molecular basis by which segments are generated in polychaetes during larval development, adult growth and regeneration.
		One approach we have taken is to determine whether genes involved in the segmentation process of arthropods influence segment formation in polychaetes.
	www.hawaii.edu /zoology/faculty/seaver.htm (447 words)

	Evolutionary developmental Biology
		Segmentation seems to work in a complex way: first the front and rear body halves are identified, then each half is halved again.
		Segment polarity genes (wingless, engrailed) which specify the polarity within a segment - so the unit, as with bithorax seems to be half a segment.
		Does this mean a common ancestry for flies and man? The organisation of the rhombomeres (segments) in the chick and mouse hindbrain is such that boundaries correspond to the edges of homeobox gene expression.
	www.leeds.ac.uk /chb/lectures/edb16.html (3140 words)

	Segmentation in Drosophila: The maternal legacy
		Segment polarity genes- Within each segment either the anterior or posterior half is duplicated.
		At the time of cellularization there is no morphological evidence for segmentation or differentiation but cells at that stage are determined with respect to the segment they will form in the adult and in the larval fly.
		Results from experimental manipulations of insect embryos in the 1960's and 1970's (localized irradiation, embryo ligations, cytoplasmic leakage, and cytoplasmic transplantation experiments) suggested that there were determinants localized in the cytoplasm at the anterior and posterior poles of the eggs which had long range effects on the fate of the entire embryo.
	www.ucalgary.ca /UofC/eduweb/virtualembryo/D_m_segment_I.html (2496 words)

	Segmentation in Drosophila: Zygotic gene expression
		The activation of the pair-rule genes in striped patterns by the maternal coordinate genes and gap genes is the first sign of segmentation in the embryo.
		The expression patterns of the segment polarity genes engrailed (en) and wingless (wg) are established through positive and negative transcriptional regulation by the pair-rule genes.
		The regulation of the segment polarity genes by the pair-rule genes is only the first stage of regulation.
	www.ucalgary.ca /UofC/eduweb/virtualembryo/D_m_segment_II.html (2489 words)

	The Biology Of Annelids
		Unless they have spend time sampling ponds and mud flats, or scuba diving on coral reefs, few people realize that one group of worms, the annelids, is one of the great branches of animal life with many thousands of species.
		This technique shows many details of annelid functional biology: food being moved along the intestine by peristaltic contractions; the circulatory system including capillary beds where oxygen is picked up (worms breath through their skins); and excretory organs that act as miniature kidneys to remove urea.
		Their elongate, segmented body plan and other body features have allowed annelids to specialize at burrowing through substrates, and to radiate into other ecological niches.
	ebiomedia.com /prod/BOanelids.html (1307 words)

	Williams Biology Faculty and Staff Savage
		The long-term objective of my research is to investigate the cellular and molecular processes that control annelid development with an emphasis on understanding the evolution of segmental pattern formation.
		Much of what is known about segmentation in annelids comes from studies in highly derived body plan of the leech.
		The divergent roles of the segmentation gene hunchback.
	www.williams.edu /Biology/Faculty_Staff/rsavage/rsavage.shtml (510 words)

	TRIZ in Biology teaching
		Segmentation - the reproductive organs can be made of more (and smaller) units so that there will be many more, smaller, offspring which will give each individual a greater chance of survival.
		Segmentation - which could suggest increasing the length of the toes, a very noticeable tendency in birds which tend to have their legs placed relatively far back on the body but need to keep their overall weight as low as possible.
		The students also made comments on the approach, pointing out that many of their solutions appeared to be available in nature already (though this may indicate that the students were not able to escape their biological environs).
	www.triz-journal.com /archives/2000/09/a (4225 words)

	Dr. Cordelia Rauskolb
		Segmentation serves to subdivide tissues into a series of repeating building blocks along either the body axis, or in some cases, the appendage axis, whereupon each basic unit can then be further elaborated upon during development.
		This requirement for a segmentally repeated pattern of Notch activation highlights the importance in establishing appropriately patterned expression of the regulators of Notch activation.
		Odd-skipped is of special interest because odd-skipped is required for embryonic segmentation in Drosophila and is expressed in a segmentally repeated pattern in both embryos and in leg discs.
	mbclserver.rutgers.edu /Waks/Rauskolb (1216 words)

	Untitled Document (Site not responding. Last check: 2007-10-26)
		The first reports of segmentation patterning genes in Drosophila melanogaster drew Dr. Strecker away from the chick to the fruit fly.
		With the emerging importance of stem cell research and its direct application to human medicine, bioethics is rapidly influencing the scope of basic research and medicine alike.
		Given the growing importance of bioethics, students in Developmental Biology at SMU are asked to engage in research and debate on issues that relate to basic and medical research in the 21 st century.
	www.smu.edu /biology/tstrecker/tstrecker.htm (1270 words)

	Biology 132 Handout Chapter 16 (Site not responding. Last check: 2007-10-26)
		This cell, with the nucleus of an adult but the environment of an egg, was induced to divide, was transplanted into a ewe and developed into a fully formed sheep.
		An example of differential gene expression: Role of differential gene expression in body segmentation: In some animals the segments of the body are very different, one from the next and this is the case in Drosophila.
		segment polarity genes — determine the boundaries and the anteroposterior organization of the segments.
	www.sewanee.edu /Biology/berner/Biology132/handouts/chapter16.html (1055 words)

	Schumacher college - Oscillators in Animal Segmentation
		This suggests that the dynamical principles of sequential segmentation might be equivalent throughout the animal kingdom although most of the genes involved in segment determination differ between distant phyla.
		Sequential segmentation in invertebrates occurs as follows: at the beginning of the segmentation process, the embryo shows very few segments or no segmental structure at all.
		However, the mechanism of invertebrate sequential segmentation remains elusive, in spite of some experimental evidence in favor of a CO-type mechanism from dissection and heat shock experiments in insects.
	www.schumachercollege.org.uk /HolisticScience/Johan.html (5288 words)

	Pharyngula::Strigamia maritima
		They're also analyzing segmentation in embryogenesis, and finding as expected that many of the same molecules we've found in other arthropods and in vertebrates and every other segmented animal are present here.
		One thing they have discovered is that segmentation proceeds from anterior to posterior, and the animal probably uses something like a segmentation clock to tick off segments.
		One of the surprises in analyzing segmentation in Drosophila was the presence of the pair rule genes—genes that are turned on in every other segment and create a two segment periodicity.
	pharyngula.org /index/weblog/comments/strigamia_maritima (1059 words)

	Tautz/Refs.
		Posterior segmentation of the Drosophila embryo in the absence of a maternal posterior organizer gene.
		Segmentation gene expression in the housefly Musca domestica.
		The genetic population structure of the grey mouse lemur (Microcebus murinus), a basal primate from Madagascar.
	www.uni-koeln.de /math-nat-fak/genetik/groups/Tautz/public.html (2846 words)

	MPIbpc 25 Years - Molecular Developmental Biology
		These act to control the expression of an interacting cascade of zygotic segmentation gene activities which subdivide the embryo into a series of increasingly smaller domains at a stage when all cells of the embryo are arranged in a single epithelial layer.
		The first zygotic segmentation genes which are activated in response to the maternal transcription factors encode also transcription factors which, however, act as repressors within the cis-acting control regions of the other zygotic segmentation genes.
		Eventually, the segmentation gene cascade culminates in a series of evenly spaced stripes which provide cell-specific positional information along the entire axis of the embryo to control genes involved in cell-cell communication events and genes which refine the position-dependent differentiation programm by regulating structural genes.
	www.mpibpc.gwdg.de /inform/25years/Jaeckle.html (530 words)

	Developmental Biology Lab
		The molecules that are important in the development and specification of the segmental body plan of the Drosophila embryo have been discovered and analyzed by looking for mutants that specifically disrupt that body plan.
		The analysis of these genes showed that the specification of the segments of the fly embryo is carried out through a cascade of transcription factors that delineate regions of the embryo and ultimately regulate the genes responsible for giving each segment its individual identity.
		The head segments of the developing embryo involute during late gastrulation and so they are internal to the thoracic segments.
	www.brynmawr.edu /biology/devbiology/labs/drosophila1.html (2216 words)

	Organismal Biology Course Descriptions
		In Developmental Biology the basic aspects of morphogenesis including cell movements and cell interactions in determination, differentiation, and pattern formation are discussed with examples from vertebrates, invertebrates and plants.
		We also examine the impact of recent discoveries in the field of molecular biology, such as the role of homeotic and segmentation genes in development and segmentation of organisms.
		Prerequisites: Biology 131 and 132; Chemistry 101 and 231.
	www.holycross.edu /departments/biology/website/biocourses/biomajorganismal.html (1055 words)

	ScienceWeek
		This segmental pattern of the body axis is established early in embryogenesis through the rhythmic production of the somites, paired blocks of paraxial mesoderm which bud off sequentially from the anterior extremity of the presomitic mesoderm.
		The segmentation clock drives the periodic transcription in the presomitic mesoderm of so-called "cyclic genes", most of which are related to the Notch signalling pathway.
		Early cell divisions of the fertilized egg, establishment of head-to-tail polarity, and the genetic circuit for body segmentation have all been modified, apparently as adaptations to the parasitic life-style.
	scienceweek.com /2003/sc031024-1.htm (531 words)

	NYU \| Department of Biology \| Faculty \| Stephen Small
		The segmentation genes we study are distributed in asymmetric expression domains along the anterior-posterior axis.
		in developmental biology in 1988 from the University of Cincinnati.
		At the undergraduate level, I teach an upper level course in Developmental Biology with Dr. Benfey, and participate in core courses such as Principles of Biology and Molecular and Cell Biology, which are team-taught.
	www.nyu.edu /fas/dept/biology/faculty/small (1008 words)

	Integrative and Comparative Biology: Unsegmented annelids? Possible origins of four lophotrochozoan worm taxa
		Despite this paradigm shift, the phylogenetic importance and evolutionary plasticity of segmentation still has not been examined in a phylogenetically rigorous manner with a sufficient number of taxa to permit a clear understanding of its role in protostome evolution.
		For these four groups, the interpretation of how their bodies are segmented (or not segmented) has been fundamental to judgments about their phylogenetic position.
		At some point, all four taxa have been considered to be derived annelids, suggesting that their body architectures are secondarily derived from a segmented ancestor.
	www.findarticles.com /p/articles/mi_qa4054/is_200206/ai_n9119129 (1203 words)

	BCM - Developmental Biology - Randy L. Johnson
		Present efforts to understand the segmentation mechanisms in our laboratory include functional characterization of novel families of transcription factors expressed in the presomitic mesoderm.
		Evrard YA, Lun Y, Aulehla A, Gan L, Johnson RL (1998) lunatic fringe is an essential mediator of somite segmentation and patterning.
		Pressman CL, Chen H, Johnson RL (2000) LMX1B, a LIM homeodomain class transcription factor, is necessary for normal development of multiple tissues in the anterior segment of the murine eye.
	www.bcm.edu /db/db_fac-johnson.html (453 words)

	Integrative and Comparative Biology: Poster Abstracts
		Arthropods, chordates and annelids are the three segmented phyla in the animal kingdom.
		Examination of Drosophila segmentation genes in vertebrates has not yielded any striking evidence for a common segmented ancestor of vertebrates and arthropods, but a recent article, which shows the involvement of Delta and Notch in the segmentation of the spider Cupiennius salei, supports the homology of segments.
		To examine a possible ancestral function of the Notch-Delta pathway in segmentation, it is important to examine members of the third major phylum of segmented animals, the annelids.
	www.findarticles.com /p/articles/mi_qa4054/is_200412/ai_n9520517/pg_68 (1197 words)

	Charles Kimmel
		Ongoing work is to understand the origin of segmental patterning of the hindbrain and pharynx, and the specification and morphogenesis of the head skeleton.
		Whereas segmentation has long been known to be a prominent component of developmental patterning of the head, we do not yet understand how the segments are initially patterned, and by what cells.
		Signaling by Fgf3 and Fgf8 is required for segmental patterning in the hindbrain, shown in whole mount with anterior to the left.
	www.neuro.uoregon.edu /ionmain/htdocs/faculty/kimmel.html (1497 words)

	Multiscale Segmentation of the Aorta in 3D Ultrasound Images
		Fast, reliable segmentation of the abdominal aorta from three dimensional ultrasound remains a difficult problem.
		Standard methods based on local information like thresholding, region growing or active contours fail in separating the arteries from the veins and suffer from the lack of homogeneity of the vessel intensity and from the partial contour information.
		After an interactive selection of the desired lines, a model of the aorta is generated using the radii information and compared to a manual segmentation.
	lmi.bwh.harvard.edu /papers/papers/krissianEMBS03.html (270 words)

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