Embryo organogenesis

Special morphogenetic factors seem also to exist in other induction systems. In all vertebrate embryos organogenesis of the cartilageneous vertebral column has been found to depend on the inductive activity of the spinal cord and the notochord (Strudel, 1967). Semitic mesenchyme isolated from early chick embryos does not form cartilage in contrast to somites taken from older embryos. In isolated somitic mesenchyme from 2- to 3-day-old embryos the formation of cartilage can be induced by extracts from spinal cord and notochord (Strudel, 1962). The chemical nature of the inducer is not yet known. Metachromatic... 

FGF (22 members) FGFs require heparan sulfate to activate their receptors FGFR Four members expressed as a number of splice variants Proliferation of many cell types. Embryo patterning and organogenesis, bone development, angiogenesis... 

Exposure to the fetus in the first 2 weeks after conception may have an all or nothing effect (i.e., could destroy the embryo or have no ill effect). Exposure during the period of organogenesis (18 to 60 days postconception) may result in structural anomalies (e.g., methotrexate, cyclophosphamide, diethylstilbestrol, lithium, retinoids, thalidomide, certain antiepileptic drugs, and coumarin derivative). 

Segment 11 teratogenicity study. This concentrates on the most sensitive part of gestation, from the time of implantation imtil major organogenesis is complete. This is the period during which a test substance is most likely to cause malformation of the embryo. Exposure of the mother to the test substance is usually confined to this period. Conventionally, the study is conducted in rats and rabbits. Rabbits are intolerant to antibiotics and the mouse is an acceptable alternative in most cases. 

Diethyl phthalate administered in the diet to rats during major organogenesis increased the incidence of fetal lumbar ribs only at 3200mg/kg/day, a maternally toxic dose. In another report, there also was an increased incidence of supernumerary ribs, but no other embryo/fetal effects, in the offspring of rats fed 5% DEP on gestational days 6-15 maternal toxicity was evident as reduced body weight gain. ... 

Fleeman TL, Cappon GD, Chapin RE et al (2005) Effects of feed restriction during organogenesis on embryo-fetal development in the rat. Birth Defects Res B Dev Reprod Toxicol 74 42 49... 

New DA (1978) Whole-embryo culture and the study of mammalian embryos during organogenesis. Biol Rev Camb Philos Soc 53(1 ) 81-122... 

The embryo-fetal development study aims to detect adverse effects on pregnant females (i.e., maternal toxicity) and on the development of embryos and fetuses (i.e., embryo-fetal death, altered growth, and structural changes) consequent to exposure of the female during organogenesis. 

Systematic screen for novel genes required in pattern formation, organogenesis and differentiation processes of the mouse embryo... 

Boron may be an essential nutrient in several species of aquatic vertebrates. Insufficient boron (<3 pg B/L 62 pg B/kg ration) interfered with the normal development of the South Afiican clawed frog (Xenopus laevis) during organogenesis, and substantially impaired normal reproductive function in adult frogs (Fort et al. 1998). Impaired growth of rainbow trout (Oncorhynchus mykiss) embryos was documented at <90 pg B/L, and death of zehrafish (Brachydanio rerio) embryos at <2 pg B/L (Rowe et al. 1998). 

Fig. 25.3 The pathways that can be taken in the development of plant tissue and cell cultures starting from a part of a plant (explant). The explant can via direct embryogenesis or oganogenesis form embryos or shoot and roots, respectively, which can be converted into plants. In another path, the explant can form a callus, which can then be used to form a suspension culture. In addition, indirect organogenesis or embryogenesis of the callus can lead to plant formation...

Rogers JM, Taubeneck MW, Daston GP, Sulik KK, Zucker RM, Elstein KH, Jankowski MA, Keen CL (1995) Zinc deficiency causes apoptosis but not cell cycle alterations in organogenesis-stage rat embryos effect of varying duration of deficiency. Teratology, 52(3) 149-159. 

The susceptibility of both an embryo and a fetus to a teratogen is variable, depending on the stage of development when exposure occurs. For gross anatomical abnormalities, the critical periods of organogenesis are the most susceptible to exposure, whereas other types of abnormality may have other critical periods for exposure. 

The sensitivity of the embryo to the induction of morphological defects is increased during the period of organogenesis. This period is essentially the time of the origination and development of the organs. The critical period graph (Figure 13.7) demonstrates this point and defines the embryonic and fetal periods. 

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