Embryonic Resistance to Chemical and Physical Factors: Manifestation, Mechanism, Role in Reproduction and in Adaptation to Ecology

Abstract

Chemical and physical factors may adversely affect embryonic development. As an example of chemical factors, the effects of diabetic metabolic factors on embryonic development in mammals was reviewed. The existence of a stage-dependent reaction of embryos was found. At preimplantation stages diabetic metabolic factors are embryotoxic and lethal, and the blastocysts reacted by an "all-or-none" response. Early somite embryos showed a higher resistance to the effects of diabetic metabolic factors resulting in various types of malformations. Both groups of embryos showed a very high sensitivity to the effects of combined diabetic metabolic factors. Congenital defects in term foetuses were lower than those observed during middle phases of pregnancy because some of the severely malformed embryos resorb during gestation. The effects of temperature on embryonic development were presented as an example of physical influences. In man, hyperthermia in pregnancy seems to correlate with defects in the development of the nervous and skeletal systems. In domestic animals, changes in environmental temperature correlated with depressions of reproduction rate. In laboratory animals, hyperthermia caused the development of congenital malformations. Stage-dependent as well as genetic differences in embryonic susceptibility to hyperthermia were found. Critical periods in sensitivity of embryos to hyperthermic influences were also observed. It has been shown that, in spite of similar external manifestations of the reaction of embryos to effects of diabetes and hyperthermia, the mechanism of these reactions was different. High resistance of early reptile and bird embryos to influences of temperature was considered as an example of morphofunctional adaptations in early embryogenesis of vertebrates to their development in terrestrial conditions.

Lethality of inappropriate plasma exposure on chicken embryonic development

“…This is likely due to the establishment of a complete embryo structure by the end of stage HH 20, which would result in increased resistance to the harmful external factors. In addition, this is supported by the facts that embryos have stage-dependent resistances to various external factors during embryogenesis [ 12 – 14 ]. But we are not sure whether mammals have stage-dependent resistance to non-thermal DBD plasma because the embryonic development of mammals is different from that of chickens.…”

“…When incubation starts, embryonic development continues, the embryo contains all organs needed to sustain life after hatching and the majority of these organs can be easily identified by the end of Hamburger-Hamilton (HH) stage 20 [ 10 ]. During embryonic development, a stage-dependent reaction on chemical and physical factors was found in mammals [ 12 ]. Unlike mammals, chicken embryos have no preimplantation stages, but resistance of chicken embryos at different stages of development to various external forces [ 13 ] and an age-related cellular resistance to viral infections were also found during chicken embryogenesis [ 14 ].…”

A Matter of Privilege: Infant Mortality in the Garrison Town of Gibraltar, 1870-1899

“…The underlying causes of stillbirths are complex and often correlated with an array of biological factors (sex, age and parity of the mother, birth spacing, father's age, multiple births, Rh incompatibility), social factors (socioeconomic status, nutrition), and environmental factors. 103 In general, stillbirths become another proxy measure for women's underlying physiological constitution.…”