(n.) A small fishlike animal (Amphioxus lanceolatus), remarkable for the rudimentary condition of its organs. It is the type of the class Leptocardia. See Amphioxus, Leptocardia.
Example Sentences:
(1) Phylogenetic comparisons of 18S ribosomal RNA sequences from two hagfishes, two lampreys, a tunicate, a lancelet, and a number of gnathostomes support the monophyly of the cyclostomes.
(2) The segmented trunk muscle (myotome muscle) of the lancelet (Branchiostoma lanceolatum), a pre-vertebrate chordate, was studied in order to gain information regarding the evolution of excitation-contraction (EC) coupling.
(3) The significance of the presence of rhabdomeric and ciliary photoreceptors in the lancelet brain is discussed.
(4) We have determined the complete sequences of 5S rRNAs from a lamprey (Lampetra reissneri), a lancelet (Branchiostoma belcheri), silkworms (Philosamia cynthia ricini, Bombyx mori, Antheraea pernyi), and a silkworm hybrid (artificially fertilized hybrid species of Philosamia cynthia ricini male x Bombyx mori female), as well as those of cotton seeds (Gossypium hirsutum L.).
(5) Nerve endings of epithalamic, hypothalamic and spinal neurosecretory areas were studied by light and electron microscopy in various vertebrates (from fishes up to mammals) including the lancelet.
(6) A third photoreceptive cell of the lancelet, the lamellate cell, is of ciliary type.
Primitive
Definition:
(a.) Of or pertaining to the beginning or origin, or to early times; original; primordial; primeval; first; as, primitive innocence; the primitive church.
(a.) Of or pertaining to a former time; old-fashioned; characterized by simplicity; as, a primitive style of dress.
(a.) Original; primary; radical; not derived; as, primitive verb in grammar.
(n.) An original or primary word; a word not derived from another; -- opposed to derivative.
Example Sentences:
(1) Cloacal exstrophy, centered on the maldevelopment of the primitive streak mesoderm and cloacal membrane, results in bladder and intestinal exstrophy, omphalocele, gender confusion, and hindgut deformity.
(2) Evx-1 RNA is first detected shortly before the onset of gastrulation in a region of ectoderm containing cells that will soon be found in the primitive streak.
(3) As an extension of the previous study which indicated that mesoglea is a primitive basement membrane which has retained some characteristics of interstitial extracellular matrix, the present study was undertaken to analyze the role of mesoglea components during head regeneration in Hydra vulgaris.
(4) neuroblastomas, primitive neuroectodermal tumours (PNETs), rhabdomyosarcomas and malignant lymphomas.
(5) We concluded that the primitive eukaryote D.discoideum contains proteins which show functional and physical similarity with the alpha-subunits of vertebrate G-proteins.
(6) Mechanisms are suggested whereby rudimentary appetitive programs already encoded along facing dendrite membrane pairs within the specialized intrafascicular milieu, may trigger and control nipple search and suckling in the still blind and only primitively mobile neonate.
(7) Thus, the progeny of infected primitive multipotential cells are competent to express integrated proviruses.
(8) Multiple tuberculomas have simulated either an alcoolic encephalopathy in one case or a primitive cerebral tumour in another one.
(9) This increased cell flow down the early stages of the red cell pathway in CML suggests that heightened proliferation and differentiation of primitive hemopoietic cells may be a more general phenomenon than previously suspected in this disease.
(10) The Lerner & Lerner Scale for assessing primitive defenses is reviewed.
(11) Only tumors of astrocytic lineage like astrocytomas and glioblastomas, or tumors of mixed lineage as oligo-astrocytomas and multipotential primitive neuroectodermal tumors (PNET) expressed TNF-alpha-like immunoreactivity.
(12) This epithelial cell was tentatively identified as primitive extraembryonic endoderm by its ultrastructural appearance and its possession of cytokeratin intermediate filaments.
(13) The long-term culture corresponded to mouse MXT and MCF-7 cell lines whereas the primary culture corresponded to primitive breast cancers squashed onto histologic slides and maintained in cultures for between 12 and 48 h. Cell proliferation was evaluated by means of digital cell image analysis of Feulgen-stained nuclei.
(14) From these facts, it was concluded that the follicular, as well as acanthomatous, ameloblastoma is liable to undergo squamous differentiation, whereas the plexiform ameloblastoma remains in primitive stage of tumor differentiation.
(15) A cluster of spermatogonia may be derived from one primitive germ cell and it develops round a "Sertoli" cell.
(16) Shielded marrow self renewal capacity, a measurement reflecting primitive hematopoietic stem cell function, remained depressed and did not recover with time.
(17) In a 3-year-old child, a rare combination of a Dandy-Walker syndrome, a primitive trigeminal artery and a facial haemangioma was found.
(18) As the histochemical and ultrastructural findings are non specific, we believe, according to recent opinions, that this tumor could originate in a very primitive cell, able to differentiate to endocrine or exocrine elements, almost always incompletely.
(19) It is likely that the development of these malignancies is an expression of the multipotential nature of primitive germ cells.
(20) Morphology of the mature spermatozoon is modified from that of the classic primitive or ect-aquasperm type by having 1) the acrosome embedded in the nucleus (the only known example within the Mollusca), 2) a deep basal invagination in the nucleus containing proximal and distal centrioles and an enveloping matrix (derived from the rootlet), 3) laterally displaced periaxonemal mitochondria, and 4) a tail extending from the basal invagination of the nucleus.